Method and application for growing carbon nanotubes by using a core-shell structure catalyst supported on the surface of carbon fiber

Abstract

The present invention discloses a method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fibers, as well as a carbon nanotube-carbon fiber multi-scale reinforcement prepared based on this method and its applications. The implementation method of the present invention includes the following steps: after the carbon fibers are surface-activated, they are first uniformly impregnated in a solution of precursor A0 and the solvent is dried, and then thermally reduced in an airtight manner to convert precursor A0 into the core component A of the catalyst; next, the carbon fibers loaded with component A are sent into a solution of precursor B0 again for uniform impregnation and drying of the solvent, and the same thermal reduction method is used to form the shell component B of the catalyst. Using this method can effectively utilize the different catalytic properties of different components, thereby growing carbon nanotubes with regular structures and high yields on the surface of carbon fibers, while reducing the co-generation of amorphous carbon impurities and reducing the damage suffered by carbon fibers during this process.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber surface modification, and particularly to a method and application for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fibers. Background Art

[0002] The statements in this section merely mention the background art related to the present invention and do not necessarily constitute prior art.

[0003] As one of the emerging high-performance materials that have received wide attention, carbon fibers have been widely used in weaponry, aerospace, building reinforcement, geological mining, vehicles and ships, and sporting goods. However, its most important application form, carbon fiber reinforced composites, is limited in various mechanical properties by the poor bonding of the fiber / matrix interface. Growing a carbon nanotube network in-situ on the surface of carbon fibers to achieve nano-scale reinforcement of the "interface phase" with a certain thickness, that is, the "carbon nanotube-carbon fiber multi-scale reinforcement", has become one of the most promising interface strengthening methods. The preparation method of this multi-scale reinforcement has been realized continuously and has advantages such as easy operation and low equipment cost.

[0004] The catalyst is the core element for preparing carbon nanotube-carbon fibers. Under its catalytic action, carbon source molecules are divided into active carbon units, and these carbon units diffuse in the catalyst particles and assemble into a carbon nanotube structure on the surface of carbon fibers. Currently, widely used carbon nanotube catalysts include magnetic nanoparticles such as iron, cobalt, nickel, and non-magnetic nanoparticles such as copper. The catalyst is formed in-situ on the surface of carbon fibers by the conversion of precursors. Metals with different physical properties will form nanoparticles with different distributions and sizes on the surface of carbon fibers and also exhibit different catalytic behaviors. Currently, the disclosed catalysts include single-component catalysts and multi-component catalysts composed of two or more metals. However, from the perspective of a single particle, its composition structure is a homogeneous metal or alloy, that is, a catalyst with a homogeneous structure.

[0005] The currently prepared carbon nanotube-carbon fiber multi-scale reinforcements have the following problems: irregular carbon nanotube structures, uneven carbon nanotube distributions, the surface of carbon fibers being coated with a large amount of amorphous carbon impurities, and the catalyst etching the surface of carbon fibers resulting in a decrease in strength, etc. These problems will further lead to weaknesses such as internal defects, stress concentration, and poor resin infiltration in their composites. Using different metals as catalysts can avoid one or two of these problems, but other problems will correspondingly intensify, which is a difficult problem that homogeneous structure catalysts are difficult to overcome.

[0006] In summary, various homogeneous structure catalysts used in the prior art have difficulty in solving various drawbacks existing in the carbon nanotube-carbon fiber prepared by them, such as the structure, distribution, impurities of carbon nanotubes, and the damage of the catalyst to the fiber strength. The homogeneous composition structure makes it difficult to synergistically exert the catalytic performance of various metals. Summary of the Invention

[0007] In view of this, the present invention provides a method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber and its application. Due to the difference in the diffusion mechanism of activated carbon units in the surface layer and the interior of the catalyst particles, the formation of carbon nanotubes mainly depends on surface layer diffusion. The catalyst provided by the present invention has a heterogeneous core-shell structure, which can effectively improve the regularity and yield of carbon nanotubes, and at the same time reduce the formation of amorphous carbon impurities, thereby significantly improving the mechanical properties of carbon nanotube-carbon fiber multi-scale reinforcements and their composites.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber, which is characterized by including the following steps:

[0010] S1: Surface activation of carbon fiber;

[0011] S2: Uniformly impregnate the solution of precursor A 0 on the surface of the surface-activated carbon fiber, and then dry the solvent in the solution to load precursor A 0 onto the surface of the carbon fiber to obtain carbon fiber loaded with precursor A 0 ;

[0012] S3: Perform thermal reduction treatment on the carbon fiber loaded with precursor A 0 in a heating device isolated from air and filled with hydrogen, so that precursor A 0 is converted into nanoparticle A to obtain carbon fiber loaded with nanoparticle A;

[0013] S4: Send the carbon fiber loaded with nanoparticle A into the solution of precursor B 0 for impregnation, and then dry the solvent in the solution to load precursor B 0 onto the surface of the carbon fiber to obtain carbon fiber loaded with nanoparticle A and precursor B 0 ; Perform thermal reduction treatment on the carbon fiber loaded with nanoparticle A and precursor B 0 in a heating device isolated from air and filled with hydrogen, so that precursor B 0 is reduced to nanoparticle B on the outer layer of nanoparticle A, that is, carbon fiber with an A@B core-shell structure catalyst in-situ loaded on the surface is obtained;

[0014] S5: Feed the carbon fiber with the A@B core-shell structure catalyst in-situ loaded on its surface into a chemical vapor deposition furnace filled with hydrogen and gaseous carbon source, and decompose the gaseous carbon source under the action of the catalyst to form carbon nanotubes, thus obtaining the carbon nanotube-carbon fiber multi-scale reinforcement.

[0015] In the second aspect, the present invention provides a carbon nanotube-carbon fiber multi-scale reinforcement prepared by a method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of the above carbon fiber.

[0016] In the third aspect, the present invention provides a carbon fiber composite material, and the carbon fiber composite material comprises the carbon nanotube-carbon fiber multi-scale reinforcement described in the second aspect.

[0017] In the fourth aspect, the present invention provides the applications of the above carbon fiber composite material in military equipment, aerospace, sports goods, industrial equipment, infrastructure, ships and vehicles, and new energy components.

[0018] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0019] (1) The present invention can effectively combine the different catalytic performances of the two catalyst components A and B. When a metal with uniform particle size and distribution and relatively low melting point is selected as component A (core), such as copper or copper-nickel alloy, and a metal with high catalytic efficiency is selected as component B (shell), such as nickel, a catalyst with excellent performance can be obtained; meanwhile, using a metal with a small diffusion coefficient in the carbon fiber as component A, such as copper, can significantly reduce the damage of fiber strength.

[0020] (2) The excellent catalyst prepared by the present invention can effectively improve the regularity and yield of carbon nanotubes, and at the same time reduce the formation of amorphous carbon impurities, thereby significantly improving the mechanical properties of the carbon nanotube-carbon fiber multi-scale reinforcement and its composite materials.

[0021] (3) The preparation method of the carbon nanotube-carbon fiber multi-scale reinforcement described in the present invention has good adaptability to the existing mainstream process operations and process equipment, is simple to operate, has low process requirements, and has the conditions for continuous preparation. Therefore, it has the potential for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0023] Figure 1 It is a schematic diagram of the mechanism of the process described in the present invention, and the right-side inset is the element scan diagram of the catalyst obtained in step 4 of Example 1;

[0024] Figure 2 (a) Transmission electron microscope image of carbon nanotubes in the carbon nanotube-carbon fiber multi-scale reinforcement obtained in Example 1, Figure 2 (b) Transmission electron microscope image of carbon nanotubes in the carbon nanotube-carbon fiber multi-scale reinforcement obtained in Comparative Example 2;

[0025] Figure 3 (a) Secondary electron scanning electron microscope image of the surface of the carbon nanotube-carbon fiber multi-scale reinforcement obtained in Example 1, Figure 3 (b) Secondary electron scanning electron microscope image of the surface of the carbon nanotube-carbon fiber multi-scale reinforcement obtained in Comparative Example 2. Detailed implementation manners

[0026] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0027] As introduced in the background art, various homogeneous structure catalysts used in the prior art are difficult to solve the various disadvantages existing in the carbon nanotubes-carbon fibers prepared by them, such as the structure, distribution, impurities of the carbon nanotubes, and the damage of the catalyst to the fiber strength. Based on this, the present invention provides a method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fibers, including the following steps:

[0028] S1: Activate the surface of the carbon fiber to make its surface have polar functional groups and rough grooves, which is convenient for the penetration of the subsequent precursor solution and the attachment of the reduced nanoparticles;

[0029] S2: Uniformly impregnate the solution of precursor A 0 on the surface of the activated carbon fiber, and then dry the solvent to load the solute precursor A 0 onto the fiber surface;

[0030] S3: Perform a thermal reduction treatment on the carbon fiber loaded with precursor A 0 in a heating device isolated from air and filled with hydrogen, so that precursor A 0 is converted into nanoparticles A;

[0031] S4: Send the carbon fiber loaded with nanoparticles A into the solution of precursor B 0 for impregnation, and then dry the solvent to load precursor B 0 onto the fiber surface; perform a thermal reduction treatment on the carbon fiber loaded with nanoparticles A and precursor B 0 in a heating device isolated from air and filled with hydrogen, so that precursor B 0The outer layer of nanoparticle A is reduced to nanoparticle B; the obtained carbon fiber is collected, and thus the carbon fiber with the A@B core-shell structure catalyst in-situ loaded on the surface is obtained.

[0032] S5: Feed the carbon fiber with the A@B core-shell structure catalyst in-situ loaded on the surface into a chemical vapor deposition furnace filled with hydrogen and gaseous carbon source, and decompose the carbon source under the action of the catalyst to form carbon nanotubes; collect the obtained fiber, which is the carbon nanotube-carbon fiber multi-scale reinforcement.

[0033] In some embodiments, the above steps can be carried out separately or continuously on a continuous device. When carried out continuously, the traveling speed of the carbon fiber tow is 5 - 25 cm / min, preferably 15 - 20 cm / min.

[0034] In some embodiments, the carbon fiber is any one of T300 grade, T700 grade, T800 grade, and T1000 grade, the number of its filaments is any one of 1K, 3K, 6K, and 12K, and its form is any one of short-cut carbon fiber, continuous carbon fiber, carbon fiber fabric, and carbon fiber paper; the carbon fiber is un-sized carbon fiber or carbon fiber after desizing of commercial carbon fiber.

[0035] In some embodiments, the method for surface activation in step S1 is electrochemical oxidation treatment method or chemical oxidation method.

[0036] In some embodiments, the method for surface activation in step S1 is preferably electrochemical oxidation treatment method, and the specific treatment method is: using the carbon fiber as the anode and graphite as the cathode, the charge density in the carbon fiber is 50 - 150 C / g, the electrolyte is deionized aqueous solution of ammonium dihydrogen phosphate, diammonium hydrogen phosphate or ammonium bicarbonate, and its concentration is 2 - 6 wt.%; preferably, the charge density is 80 - 120 C / g, and the electrolyte is 3 - 5 wt.% deionized aqueous solution of ammonium dihydrogen phosphate.

[0037] In some embodiments, the precursor A 0 and the precursor B 0 are respectively any one or more of metal chlorides, metal nitrates, and metal metallocenes corresponding to the two components A and B. The solvent in the precursor solution is any one of deionized water, ethanol, and acetone, and the total concentration of metal ions in the precursor solution is 0.01 - 0.1 mol / L; preferably, the precursor is metal nitrate, the solvent is ethanol, and the total concentration of metal ions in the solution is 0.02 - 0.05 mol / L.

[0038] In some embodiments, the component A is a mixture of any one or more of copper, iron, cobalt, and nickel, and the component B is a mixture of any one or more of copper, iron, cobalt, and nickel different from component A. Preferably, the component A is copper, cobalt, or a copper-nickel alloy with a molar ratio of 1-5:1, and the component B is nickel, iron, or a copper-nickel alloy different from component A and with a molar ratio of 0.2-1:1.

[0039] In some embodiments, the heating device in steps S3 and S4 is a tube furnace. The temperature of the thermal reduction treatment is 350-500 °C, the flow rate of hydrogen is 0.2-1.5 L / min, and the time of the thermal reduction treatment is 2-15 min.

[0040] In some embodiments, the gaseous carbon source is any one or more of methane, acetylene, carbon monoxide, and gaseous ethanol, and the flow rate ratio of hydrogen to the gaseous carbon source is 0.8-3:1. Preferably, the carbon source is acetylene, and the flow rate ratio of hydrogen to the gaseous carbon source is 1-1.5:1.

[0041] In some embodiments, the furnace temperature of the chemical vapor deposition furnace is 500-750 °C, and the chemical vapor deposition reaction time is 2-15 min; preferably, the furnace temperature of the chemical vapor deposition furnace is 600-650 °C, and the chemical vapor deposition reaction time is 3-10 min.

[0042] In another embodiment of the present invention, a carbon nanotube-carbon fiber multi-scale reinforcement prepared by a method for growing carbon nanotubes on the surface of the above carbon fiber loaded with a core-shell structure catalyst is provided.

[0043] In another embodiment of the present invention, an application of the above carbon nanotube-carbon fiber multi-scale reinforcement in the preparation of composites is provided, including but not limited to directly using the continuous fiber obtained by the continuous equipment of the present invention to prepare a unidirectional composite material, or making the carbon fiber into a fabric and then using it for the preparation of a composite material. The obtained carbon nanotube-carbon fiber multi-scale reinforcement is mainly used in the preparation of resin-based composites, and can also be used to prepare composites by compounding with other matrices.

[0044] In order to enable those skilled in the art to more clearly understand the technical solutions of the present invention, the following will further describe the present invention in detail with specific embodiments.

[0045] Example 1

[0046] Step 1: Desize the commercial T800 grade carbon fiber (12K) and send it into the electrolytic cell. A 5 wt.% ammonium dihydrogen phosphate solution is used as the electrolyte in the electrolytic cell, a graphite plate is used as the cathode, and the continuously advancing carbon fiber filament bundle is used as the anode. The charge density on the carbon fiber is 100 C / g. Subsequently, wash off the electrolyte in deionized water and dry it in an oven at 70 °C.

[0047] Step 2: Soak the activated carbon fiber obtained in Step 1 in an anhydrous ethanol solution containing 0.03 mol / L copper nitrate for 10 min, and then dry it in an oven at 70 °C.

[0048] Step 3: Feed the carbon fiber with copper ions obtained in Step 2 into a tube furnace (A) for treatment for 5 min. Hydrogen is introduced into the furnace at a flow rate of 0.6 L / min, and the furnace temperature is 400 °C.

[0049] Step 4: Soak the carbon fiber with nano copper particles obtained in Step 3 in an anhydrous ethanol solution containing 0.02 mol / L nickel nitrate for 10 min, then dry it in an oven at 70 °C, and feed it into a tube furnace (B) with the same settings as the tube furnace (A) for treatment for 5 min.

[0050] Step 5: Feed the carbon fiber carrying the catalyst obtained in Step 4 into a tube furnace (C) filled with a mixed gas of hydrogen and acetylene under air isolation for treatment for 8 min. The hydrogen flow rate in the furnace is 0.4 L / min, the acetylene flow rate is 0.2 L / min, and the furnace temperature is 650 °C.

[0051] After Step 5, collect the obtained carbon fiber to obtain the carbon nanotube–carbon fiber multi-scale reinforcement.

[0052] Example 2

[0053] The difference from Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.02 mol / L copper nitrate and 0.01 mol / L nickel nitrate.

[0054] Example 3

[0055] The difference from Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.03 mol / L cobalt nitrate.

[0056] Example 4

[0057] The difference from Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.01 mol / L copper nitrate and 0.02 mol / L cobalt nitrate.

[0058] Example 5

[0059] The difference from Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.04 mol / L copper nitrate; the anhydrous ethanol solution in Step 4 contains 0.01 mol / L nickel nitrate.

[0060] Example 6

[0061] The difference from Example 1 is that: the anhydrous ethanol solution in Step 4 contains 0.02 mol / L iron nitrate.

[0062] Example 7

[0063] It is different from Example 1 in that: the absolute ethanol solution in Step 4 contains cobalt nitrate at a concentration of 0.02 mol / L.

[0064] Example 8

[0065] A continuous process for growing carbon nanotubes on the surface of continuous carbon fibers is implemented using a continuous device. In the following continuously performed steps, the traveling speed of the carbon fiber tow is set at 20 cm / min;

[0066] Step 1: The continuous non-sized T300 grade carbon fiber (3K) first passes through an electrolytic cell for surface activation, then passes through a deionized water bath for cleaning, and then is dried in an oven at 70 °C; among them, the electrolyte is a deionized aqueous solution of ammonium dihydrogen phosphate at 3 wt.%, the cathode is a graphite plate, and the charge density in the carbon fiber is 80 C / g;

[0067] Step 2: The carbon fiber treated in Step 1 then enters a mixed acetone solution of copper nitrate and cobalt nitrate and is soaked for 5 min, and then is dried in an oven at 70 °C;

[0068] Step 3: The carbon fiber treated in Step 2 is then thermally reduced in a tubular furnace with argon gas seals at both ends and filled with a hydrogen mixed gas inside for 10 min; among them, the concentration of copper ions in the solution is 0.02 mol / L, the cobalt ions are 0.02 mol / L, the temperature of the tubular furnace is 500 °C, and the hydrogen flow rate is 1 L / min;

[0069] Step 4: The carbon fiber treated in Step 3 then enters a nickel nitrate acetone solution and is soaked for 5 min, and then is dried in an oven at 70 °C, and then is thermally reduced in a tubular furnace with argon gas seals at both ends and filled with a hydrogen mixed gas inside for 10 min; among them, the concentration of nickel ions in the solution is 0.01 mol / L, the temperature of the tubular furnace is 500 °C, and the hydrogen flow rate is 1 L / min;

[0070] Step 5: The carbon fiber treated in Step 4 then enters a tubular furnace with nitrogen gas seals at both ends and filled with a hydrogen and methane mixed gas inside for carbon nanotube growth for 15 min; the temperature of the tubular furnace is 700 °C, the hydrogen flow rate is 0.7 L / min, and the methane flow rate is 0.3 L / min;

[0071] After Step 5, the product is continuously collected by a wire winding machine, and a continuous carbon nanotube-carbon fiber multi-scale reinforcement is obtained.

[0072] Example 9

[0073] Step 1: Immerse the chopped T700 carbon fiber in acetone for 24 h to remove the sizing agent, take it out and dry it in an oven at 60 °C, then immerse it in 10 wt.% hydrogen peroxide for 30 min to activate the surface, take it out and dry it in an oven at 60 °C;

[0074] Step 2: Immerse the carbon fiber obtained in Step 1 in an aqueous solution of cobalt nitrate in deionized water at 0.03 mol / L for 10 min, then take it out and dry it in an oven at 60 °C;

[0075] Step 3: Then put the carbon fiber dried in Step 2 into a closed furnace, exhaust the air and introduce hydrogen at 1.2 L / min, and heat up to 450 °C and hold for 10 min;

[0076] Step 4: Take out the carbon fiber obtained in Step 3, immerse it in an aqueous solution of iron nitrate in deionized water at 0.02 mol / L for 10 min, then take it out and dry it in an oven at 60 °C. Then put the carbon fiber into a closed furnace, exhaust the air and introduce hydrogen at 1.2 L / min, heat up to 450 °C and hold for 10 min, and then introduce acetylene at 0.8 L / min and heat up to 600 °C and hold for 10 min;

[0077] Collect the carbon fiber obtained in Step 4, which is the chopped carbon nanotube–carbon fiber multi-scale reinforcement.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.05 mol / L of copper nitrate; after Step 3, Step 4 is not carried out, and Step 5 is directly carried out.

[0080] Comparative Example 2

[0081] The difference from Comparative Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.05 mol / L of nickel nitrate.

[0082] Comparative Example 3

[0083] The difference from Comparative Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.05 mol / L of cobalt nitrate.

[0084] Comparative Example 4

[0085] The difference from Comparative Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.02 mol / L of copper nitrate and 0.03 mol / L of nickel nitrate.

[0086] Comparative Example 5

[0087] The difference from Comparative Example 1 is that: the anhydrous ethanol solution in Step 2 contains 0.03 mol / L of copper nitrate and 0.02 mol / L of nickel nitrate.

[0088] Combined with Figure 1 From the element scanning results in

[0088] and the X-ray photoelectron spectroscopy element analysis results in Table 1, it can be seen that the catalyst obtained in Step 4 of Example 1 has a core-shell structure with nickel on the outer layer and copper on the inner layer.

[0089] Table 1 Composition of the catalyst obtained in Step 4 of Example 1 characterized by X-ray photoelectron spectroscopy at different etching depths

[0090] Etching depth Cu atomic ratio in metal (at.%) Ni atomic ratio in metal (at.%) 1 nm 8 92 5 nm 33 67 9 nm 72 28 13 nm 64 36 17 nm 42 58

[0091] Table 2 is a comparison table of the graphitization degree of carbon nanotube–carbon fiber multi-scale reinforcements prepared in Examples 1-2 and Comparative Examples 1-5 of the present invention.

[0092] Table 2 Comparison table of the graphitization degree of carbon nanotube–carbon fiber multi-scale reinforcements

[0093]

[0094]

[0095] As can be seen from Table 2, the graphitization degree of the carbon nanotubes grown in the carbon nanotube–carbon fiber multi-scale reinforcements prepared with the core-shell structure catalyst loaded on the carbon fiber surface according to the present invention is significantly better (i.e., the Raman R value is smaller) compared to each of the comparative examples using homogeneous catalysts. As Figure 2 can be seen, the carbon nanotubes on the surface of the product obtained in Example 1 have a regular hollow tubular structure, while the surface of Comparative Example 2 with a single nickel component is a nanowire structure. As Figure 3 can be seen, the carbon nanotube–carbon fiber multi-scale reinforcements obtained in Example 1 are uniform in thickness, very clear, and almost free of nodules and clusters, while the carbon nanotube–carbon fiber multi-scale reinforcements prepared in Comparative Example 2 are more disordered and accompanied by a large amount of impurities. From the chemical vapor deposition (CVD) products and distribution summarized in Table 2, in the comparative examples, either the products are scarce (such as Comparative Example 1), or they are too dense and accompanied by adverse structures such as impurities and clusters, while the CVD deposition products obtained in the present invention are mainly carbon nanotubes, which are uniformly distributed and relatively dense on the carbon fiber surface.

[0096] Table 3 shows the physical properties of the carbon nanotube–carbon fiber multi-scale reinforcements prepared in Examples 1-2 and Comparative Examples 1-5 of the present invention.

[0097] Table 3 Physical properties of carbon nanotube–carbon fiber multi-scale reinforcements

[0098]

[0099]

[0100] As can be seen from Table 3, the carbon deposition amount of the carbon nanotube-carbon fiber multi-scale reinforcement prepared according to the present invention is significantly higher than that of Comparative Examples 1 and 3 using pure copper and pure cobalt catalysts, comparable to that of Comparative Examples 4 and 5 using copper-nickel alloy catalysts, and lower than that of Comparative Example 2 using pure nickel catalyst. Although Comparative Examples 2, 4, and 5 have higher carbon deposition amounts, as can be seen from Tables 2 and Figure 3 It can be seen that there are more amorphous carbon impurities in Comparative Examples 2, 4 and 5. Too little carbon nanotube growth will result in insufficient interfacial bonding of the resin, while too many carbon nanotubes and associated impurities will block the resin and prevent it from being immersed. The present invention not only avoids the large-scale generation of impurities, but also obtains more high-quality deposition products. These advantages can also be seen from the specific surface area and contact angle data in Table 3. The larger specific surface area reflects that there are fewer carbon impurities blocking the pores in the product of the present invention; the lower contact angle indicates better wettability and higher porosity, which also reflects less amorphous impurity carbon. The above data show that the carbon nanotube-carbon fiber multi-scale reinforcement prepared by the present invention has significant structural advantages over the prior art.

[0101] Table 4 is a comparison table of the interface properties of the carbon nanotube-carbon fiber multi-scale reinforcements prepared in the embodiments of the present invention and the comparative examples.

[0102] Table 4 Interface properties of carbon nanotube-carbon fiber multi-scale reinforcement

[0103]

[0104] The structural advantages in the microscopic field have greatly improved the interface performance of the carbon nanotube-carbon fiber multi-scale reinforcement prepared by the present invention. Table 4 shows that the interface shear strength and interlaminar shear strength of the carbon nanotube-carbon fiber multi-scale reinforcement prepared by Examples 1 and 2 are significantly ahead of the comparative examples. The comparison of interlaminar shear modulus shows that the carbon nanotubes prepared by the present invention have a significant reinforcement effect on the interface of the composite material, greatly improving its modulus. The strong bonding of the interface greatly improves the mechanical properties of the prepared composite material, which shows that the carbon nanotube-carbon fiber multi-scale reinforcement obtained by catalyzing the growth of carbon nanotubes using a core-shell structure catalyst loaded on carbon fibers in situ has excellent performance.

[0105] Table 5 is a comparison table of the tensile properties of the single fiber of the carbon nanotube-carbon fiber multi-scale reinforcement prepared in the embodiments of the present invention and the comparative examples after loading the catalyst and growing the carbon nanotubes.

[0106] Table 5 Tensile properties of single fiber after catalyst loading and carbon nanotube growth

[0107]

[0108] The loading of metal catalysts will lead to the weakening of the strength of carbon fibers, while the CVD process will repair the strength of carbon fibers to a certain extent. Different types of metals cause different degrees of damage. Copper causes less damage to carbon fibers than cobalt and nickel. However, the catalytic efficiency of copper is low, so the repair caused by it during the CVD process is also less. As can be seen from Table 5, Example 1 of the core-shell structure catalyst with copper as the core and nickel as the outer layer combines the advantages of both, reducing the damage caused by catalyst loading and ensuring a high repair effect. Finally, the carbon nanotube-carbon fiber multi-scale reinforcement with the highest tensile strength and modulus is obtained, and its tensile properties are even better than those of the carbon fiber used as the raw material. The enhancement of the tensile properties of the reinforcement will also enhance the mechanical properties of its composite materials.

[0109] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber, characterized in that, it includes the following steps: S1: Activate the surface of the carbon fiber; S2: Impregnate the precursor A 0 solution uniformly on the surface of the surface-activated carbon fiber, and then dry the solvent in the solution to load the precursor A 0 onto the surface of the carbon fiber, obtaining the carbon fiber loaded with the precursor A 0 ; S3: Thermally reduce the carbon fiber loaded with precursor A in a heating device that is airtight and filled with hydrogen, so that precursor A 0 is converted into nanoparticle A, obtaining carbon fiber loaded with nanoparticle A; 0 ​ S4: Feed the carbon fiber loaded with nanoparticle A into precursor B 0 and immerse it in the solution. Subsequently, dry the solvent in the solution to load precursor B 0 onto the surface of the carbon fiber, obtaining a carbon fiber loaded with nanoparticle A and precursor B 0 ; perform a thermal reduction treatment on the carbon fiber loaded with nanoparticle A and precursor B 0 in a heating device with air isolated and hydrogen filled, so that precursor B 0 is reduced to nanoparticle B on the outer layer of nanoparticle A, thus obtaining a carbon fiber with an A@B core-shell structure catalyst in-situ loaded on its surface; S5: Feed the carbon fiber with the A@B core-shell structure catalyst loaded in situ on the surface into a chemical vapor deposition furnace filled with hydrogen and a gaseous carbon source, and decompose the gaseous carbon source under the action of the catalyst to form carbon nanotubes, thus obtaining a carbon nanotube-carbon fiber multi-scale reinforcement; The precursor A 0 and the precursor B 0 are respectively any one or more of metal chlorides, metal nitrates, and metal metallocenes corresponding to the two components A and B. The solvent in the precursor solution is any one of deionized water, ethanol, and acetone, and the total concentration of metal ions in the precursor solution is 0.01 - 0.1 mol / L; The component A is any one or a mixture of copper, iron, cobalt, and nickel, and the component B is any one or a mixture of copper, iron, cobalt, and nickel different from component A.

2. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the precursor is metal nitrate, the solvent is ethanol, and the total concentration of metal ions in the solution is 0.02 - 0.05 mol / L.

3. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the component A is copper, cobalt, or a copper-nickel alloy with a molar ratio of 1 - 5:1, and the component B is nickel, iron, or a copper-nickel alloy different from component A and with a molar ratio of 0.2 - 1:

1.

4. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the heating equipment in steps S3 and S4 is a tube furnace, the temperature of the thermal reduction treatment is 350 - 500 °C, the flow rate of hydrogen is 0.2 - 1.5 L / min, and the time of the thermal reduction treatment is 2 - 15 min.

5. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the gaseous carbon source is any one or more of methane, acetylene, carbon monoxide, and gaseous ethanol, and the flow rate ratio of hydrogen to the gaseous carbon source is 0.8 - 3:1; the furnace temperature of the chemical vapor deposition furnace is 500 - 750 °C, and the chemical vapor deposition reaction time is 2 - 15 min.

6. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the carbon source is acetylene, and the flow rate ratio of hydrogen to the gaseous carbon source is 1 - 1.5:

1.

7. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the furnace temperature of the chemical vapor deposition furnace is 600 - 650 °C, and the chemical vapor deposition reaction time is 3 - 10 min.

8. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, characterized in that, the carbon fiber is any one of T300 grade, T700 grade, T800 grade, and T1000 grade, the number of filaments of the carbon fiber is any one of 1K, 3K, 6K, and 12K, and the morphology of the carbon fiber is any one of short-cut carbon fiber, continuous carbon fiber, carbon fiber fabric, and carbon fiber paper; the carbon fiber is an un-sized carbon fiber or a carbon fiber obtained by desizing a commercial carbon fiber.

9. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1, It is characterized in that It includes The surface activation method described in step S1 is an electrochemical oxidation treatment method or a chemical oxidation method.

10. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 1 It is characterized in that It includes The surface activation method described in step S1 is an electrochemical oxidation treatment method. The specific treatment method is: using carbon fiber as the anode and graphite as the cathode, the charge density in the carbon fiber is 50-150 C / g, and the electrolyte is an aqueous deionized solution of ammonium dihydrogen phosphate, diammonium hydrogen phosphate or ammonium bicarbonate, and its concentration is 2-6 wt.%.

11. The method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to claim 10 It is characterized in that The charge density is 80-120 C / g, and the electrolyte is an aqueous deionized solution of 3-5 wt.% ammonium dihydrogen phosphate.

12. A carbon nanotube-carbon fiber multi-scale reinforcement prepared by the method for growing carbon nanotubes by loading a core-shell structure catalyst on the surface of carbon fiber according to any one of claims 1-11.

13. A carbon fiber composite material It is characterized in that The carbon fiber composite material contains the carbon nanotube-carbon fiber multi-scale reinforcement according to claim 12.

14. The application of the carbon fiber composite material according to claim 13 in military equipment, aerospace, sports goods, industrial equipment, infrastructure, ships and vehicles, and new energy components.

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