CN110820322B - A method for growing carbon nanotubes on carbon fibers using sodium lignosulfonate and bimetallic catalysts - Google Patents

Abstract

The invention relates to a method for growing carbon nanotubes on carbon fibers by using the combined action of lignin and a bimetallic catalyst. The preparation method comprises the following steps: step 1: winding the carbon fiber into a vertical CVD furnace, introducing nitrogen, and keeping the temperature at 450 ℃ for 1.5h to remove a sizing agent; step 2: the carbon fiber is electrolyzed and desized and is led into an electrolytic bath, and the electrolyte is NH₄H₂PO₄Electrolyzing the aqueous solution, washing with water and drying; and step 3: loading catalyst with solute including ferric nitrate, nickel nitrate and sodium lignosulfonate and solvent including absolute alcohol, and stoving. And 4, step 4: introducing carbon fiber into a tube furnace, introducing N₂And H₂The temperature in the furnace is 450 ℃ and the time is 5min, the aim is to reduce the catalyst, then the carbon fiber is led into another tube furnace to grow the carbon nano tube, and the gas which is led in is N₂、H₂And C₂H₂The long tube time is 5 min. The method can overcome the problem of poor connection between the carbon nanotube and the carbon fiber, thereby improving the mechanical property of the treated carbon fiber.

Description

A kind of using sodium lignosulfonate and bimetallic catalyst to work together on carbon fiber Method for growing carbon nanotubes

technical field

The invention belongs to the preparation of a multi-scale combination of carbon fibers and carbon nanotubes, in particular to a method for catalyzing growth of carbon nanotubes on the surface of carbon fibers with a bimetallic catalyst and using lignin to improve the connection between carbon fibers and carbon nanotubes. This method can improve the mechanical properties of carbon fibers.

Background technique

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

Carbon fiber reinforced polymer composites (CFRPs) have excellent high specific strength, high specific modulus, light weight, fatigue and corrosion resistance, etc., and are increasingly used in aerospace, military and industrial, sporting goods such as racquet clubs and other fields. widely. Because the surface of carbon fiber after carbonization is inert, smooth and low in surface energy, when CFRPs are prepared by combining with the resin matrix, the interface phase tends to become the primary location for stress concentration and damage when subjected to external force due to poor adhesion, which seriously restricts the production of CFRPs. The development and application of CFRPS.

Therefore, the performance of carbon fiber composites mainly depends on the interface between the fibers and the matrix. A good interface connection provides structural integrity for the composite material and ensures the effective transmission and release of loads. The surface of the untreated carbon fiber is smooth, and when the composite material is subjected to stress, it is easy to cause the debonding of the carbon fiber and the matrix, which limits the further improvement of its mechanical properties. In recent years, chemical grafting of carbon nanotubes (CNTs) to form bonds with the surface of carbon fibers to improve the mechanical properties of composites has been a hot frontier scientific and technological focus. Due to the introduction of CNTs at the interface of the multi-scale reinforcement composite, the interface between the carbon fiber and the resin is increased, and a transitional buffer interface is formed at the same time, which can effectively transfer and transfer stress when subjected to external force loads, which significantly improves CFRPS. mechanical properties. In addition, due to the excellent mechanical properties, electrical properties and thermal properties of CNTs themselves, CFRP also endows CFRP with more characteristics and has a wider range of applications.

By practicing known chemical vapor deposition (CVD) methods, carbon nanotubes can be grown on the surface of carbon fibers.

The principle of growing carbon nanotubes on the surface of carbon fibers is that carbon source gases such as C ₂ H ₂ will be catalyzed by metal elements to crack out carbon atoms. Tube. To obtain the simple metal, the metal compound is first loaded on the carbon fiber, and then hydrogen is introduced for reduction to obtain the simple metal.

Zheng Linbao et al. (Study on the growth of carbon nanotubes on the surface of continuous carbon fibers and their structural properties [D]. Shandong University, 2018.) Using cobalt nitrate as catalyst, using methane as carbon source, using argon as protective gas, deposition at 650 ℃ Within 10 minutes, carbon nanotubes were grown on the surface of carbon fibers, which improved the degree of graphitization of carbon fibers.

Chinese patent document CN102199872A discloses a method for in-situ growth of carbon nanotubes on the surface of fibers. Carbon nanotubes were synthesized by using ethanol or acetone as carbon source, ferrocene as catalyst, sulfur-containing substances such as sulfur and thiophene as co-catalyst, and hydrogen or a mixture of hydrogen and other inert gases as carrier gas. This method needs to be synthesized at a high temperature of 600-1000 °C, and the reaction device uses a horizontal electric furnace, which cannot produce samples on a large scale.

SUMMARY OF THE INVENTION

In order to overcome the above problems, the present invention provides a production method with simple operation, easy replication and implementation, high efficiency and low cost. It solves the problem that the use of a single type of metal catalyst to grow carbon nanotubes at higher temperatures in the past resulted in high fiber damage, and carbon nanotubes are prone to agglomeration on the fiber surface, poor dispersibility, which seriously affects the mechanical properties of composite materials. The connection between the carbon nanotubes and the carbon fibers on the carbon fibers is not very tight, and it is easy to fall off.

For realizing the above-mentioned technical purpose, the technical scheme adopted in the present invention is as follows:

A method for growing carbon nanotubes on carbon fibers using sodium lignosulfonate and a bimetallic catalyst, comprising:

The carbon fiber is desizing, electrolytically oxidized, immersed in a mixed solution of sodium lignosulfonate and bimetallic catalyst, dried, and then carbon nanotubes are grown on the above-treated carbon fiber by chemical vapor deposition.

This application solves the problems of uneven growth of carbon nanotubes and poor connection effect in the past. The effect of using a bimetallic catalyst is obviously better and more stable than that of a single metal catalyst, and lignin is introduced to further strengthen the carbon nanotubes and carbon fibers. The connection between the two, and the production process is stable and controllable, which is convenient for continuous and industrial production.

In some embodiments, the temperature of the desizing is 450-460° C. for 1.5-2 hours to remove the resin material on the surface and improve the strength of the carbon fiber.

In some embodiments, the electrolyte is a 5-6%wt ammonium dihydrogen phosphate solution, and the electrolysis is performed for 80-90 s under the condition that the current intensity is 0.4-0.5A. It utilizes the properties of strong electrolyte of ammonium dihydrogen phosphate, and the price is relatively cheap. When electrolysis is used, because its modification degree is relatively mild, the subsequent modification effect of lignin can be effectively improved. In addition, electrolysis is easy to operate, the current intensity is controllable and stable, and it is more economical in industrial production.

The specific type of the bimetallic catalyst is not particularly limited in this application. In some embodiments, the bimetallic catalyst is composed of ferric nitrate and nickel sulfate, so as to improve the bonding interface strength of carbon nanotubes and carbon fibers and the mechanical properties of carbon fibers. performance.

In some embodiments, the molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate is 1:1:1-1.5. The growth of carbon tubes under the dual catalysts is relatively uniform, and the addition of lignin also improves the bonding interface strength of carbon nanotubes and carbon fibers.

With the increase of metal ion concentration, the catalytic efficiency improves, but when the metal ion concentration reaches a certain value, the catalytic efficiency is not improved by continuing to increase the metal ion concentration. In some embodiments, in the mixed solution of sodium lignosulfonate and bimetallic catalyst, the total concentration of metal ions is 0.01-0.05 mol/L, which improves the catalytic efficiency.

In some embodiments, the dipping time is 5-6 min, and the method is a wire running method. By controlling the wire running speed, the dipping time can be effectively controlled.

In some embodiments, the steps of the chemical vapor deposition method are: reducing the catalyst, re-growing carbon nanotubes, and finally recovering the tow with a wire take-up machine; by controlling the wire running speed, the reduction time and the long tube time are both 5min , and finally the tow is recovered with a wire take-up machine.

In some embodiments, the catalyst is reduced in a mixed gas of N ₂ and H ₂ , and the flow rate ratio of N ₂ and H ₂ is 1:1-1.2, which improves the reduction efficiency and reduction effect.

The present invention also provides the carbon nanotube/carbon fiber reinforcement prepared by any of the above methods.

The present invention also provides the application of the above-mentioned carbon nanotube/carbon fiber reinforced body in the fields of aerospace, military and industry, and sporting goods, and the sporting goods include rackets and clubs.

The beneficial effects of the present invention are:

(1) The present invention provides a kind of production method with simple operation, feasible technological process and lower cost, because this method reduces the growth temperature of carbon nanotubes, so the damage to the fiber itself is less, and the growth of carbon tubes under dual catalysts is relatively low. Evenly, the addition of lignin also improves the bonding interface strength of CNTs and CFs. This product can significantly improve the mechanical properties of carbon fiber.

(2) The operation method of the present application is simple, low in cost, universal, and easy for large-scale production.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application.

FIG. 1 is a secondary electron scanning microscope image of the carbon fiber obtained in Example 1 of the present invention. (A) Carbon fiber fabric grown with carbon nanotubes; (B) Carbon nanotubes grown uniformly on the surface of carbon fiber fabric.

FIG. 2 is a secondary electron scanning microscope image of the carbon fiber obtained in Example 2 of the present invention. (A) Carbon fiber fabric grown with carbon nanotubes; (B) Carbon nanotubes grown uniformly on the surface of carbon fiber fabric.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

As described in the background art, for the current single type of metal catalysts, the growth of carbon nanotubes at higher temperatures has high damage to fibers, and carbon nanotubes are prone to agglomeration on the surface of fibers, and the dispersibility is poor, which seriously affects the mechanical properties of composite materials. However, the connection between carbon nanotubes and carbon fibers on the carbon fibers after production is not very tight, and it is easy to fall off. Therefore, the present invention proposes a method for growing carbon nanotubes on carbon fibers by using sodium lignosulfonate and a bimetallic catalyst, comprising the following steps:

Step 1: Put the carbon fiber into a vertical CVD furnace, heat it to 450°C at a heating rate of 20°C/min for 1.5h under a nitrogen atmosphere, remove the sizing agent on the surface of the fiber, and take it out after cooling to room temperature;

Step 2: Pass the carbon fiber fabric obtained in Step 1 through an electrolytic cell filled with a concentration of 5% wt ammonium dihydrogen phosphate solution, electrolyze it for 80s under the condition of a current intensity of 0.4A, and then dry it in an oven after washing with water to remove the surface electrolyte. ;

Step 3: take the same molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate as the solute, and take absolute ethanol as the solvent to prepare a solution, the total concentration of metal ions as the catalyst is 0.05mol/L, and the lignin salt is also the same. The concentration of the same is also 0.05mol, and then the electrolytically etched carbon fiber processed in step 2 is passed into the catalyst solution for 10min, and the catalyst precursor is loaded on the surface of the carbon fiber;

Step 4: The carbon fiber treated in step 3 is first reduced by a tube furnace at 450 °C to reduce the catalyst. The flow rates of H ₂ and N ₂ are both 0.5L/min. After reduction, it is then introduced into another tube furnace with a temperature of 450 ° C for growth. Carbon nanotubes, the gases introduced into the furnace at this time are N ₂ , H ₂ and C ₂ H ₂ , and the flow rates of the gases are 0.3L/min, 0.3L/min and 0.6L/min in turn. The reduction time and long tube time are both 5min, and finally the tow is recovered by a wire take-up machine.

Wherein, in the step 2, the current intensity can be 0.1A-0.4A, preferably 0.4A, and the electrolysis time can be 60s-100s, preferably 80s.

Wherein, the total concentration of metal ions in the step 3 may be 0.01mol/L, 0.02mol/L, 0.03mol/L, 0.04mol/L and 0.05mol/L.

Wherein, the carbon nanotube growth temperature in the step 4 may be 400°C, 450°C, 500°C, and 550°C. 450°C is preferred.

The present invention will be further described in detail below with reference to specific embodiments. It should be pointed out that the specific embodiments are intended to explain rather than limit the present invention.

Example 1

Step 1: Put the carbon fiber fabric into a vertical CVD furnace, heat it to 450°C for 1.5h at a heating rate of 15°C/min under a nitrogen atmosphere, remove the sizing agent on the fiber surface, and take it out after cooling to room temperature;

Step 2: The obtained carbon fiber fabric is filled with 5% wt ammonium dihydrogen phosphate solution. The electrolytic cell was electrolyzed for 80s under the condition of the current intensity of 0.4A, followed by washing with water to remove the surface electrolyte and drying in an oven;

Step 3: take the same molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate as the solute, and take absolute ethanol as the solvent to prepare a solution, the metal ion concentration as the catalyst is all 0.05mol/L, and the lignin salt is also the same. The concentration of the same is also 0.05mol/L, then the carbon fiber after electrolytic etching processed in step 2 is passed into the catalyst solution for 10min, and the catalyst precursor is loaded on the surface of the carbon fiber;

Step 4: The carbon fiber treated in step 3 is first reduced by a tube furnace at 450 °C, and the flow rates of H ₂ and N ₂ are both 0.5L/min. After reduction, it is then introduced into another tube furnace with a temperature of 450 ° C. To grow carbon nanotubes, the gases introduced into the furnace are N ₂ , H ₂ and C ₂ H ₂ , and the flow rates of the gases are 0.3L/min, 0.3L/min and 0.6L/min in turn. By controlling the wire running speed The reduction time and the long tube time are both 5min, and the tow is finally recovered with a wire take-up machine.

FIG. 1 is a secondary electron scanning microscope image of the carbon fiber obtained in Example 1 of the present invention. (A) Carbon fiber fabric grown with carbon nanotubes; (B) Carbon nanotubes grown uniformly on the surface of carbon fiber fabric.

Example 2

Step 1: Put the carbon fiber into a vertical CVD furnace, heat it to 450°C for 1.5h at a heating rate of 15°C/min under a nitrogen atmosphere, remove the sizing agent on the surface of the fiber, and take it out after cooling to room temperature;

Step 2: The obtained carbon fiber is electrolyzed for 100s under the condition of a current intensity of 0.2A through an electrolytic cell filled with a concentration of 5% wt ammonium dihydrogen phosphate solution, followed by washing with water to remove the surface electrolyte, and drying in an oven;

Step 3: take the same molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate as the solute, and take absolute ethanol as the solvent to prepare a solution, the metal ion concentration as the catalyst is all 0.03mol/L, and the lignin salt is also the same. The concentration of the same is also 0.03mol/L, then the carbon fiber after electrolytic etching processed in step 2 is passed into the catalyst solution for 10min, and the catalyst precursor is loaded on the surface of the carbon fiber;

Step 4: The carbon fiber treated in step 3 is first reduced by a tube furnace at 450 °C, and the flow rates of H ₂ and N ₂ are both 0.5L/min. After reduction, it is then introduced into another tube furnace with a temperature of 400 ° C. To grow carbon nanotubes, the gases introduced into the furnace are N ₂ , H ₂ and C ₂ H ₂ , and the flow rates of the gases are 0.3L/min, 0.3L/min and 0.6L/min in turn. By controlling the wire running speed The reduction time was set to 5 minutes and the long tube time was set to 10 minutes, and finally the tow was recovered with a wire take-up machine.

FIG. 2 is a secondary electron scanning microscope image of the carbon fiber obtained in Example 2 of the present invention. (A) carbon fiber fabric with growing carbon nanotubes; (B) carbon nanotubes dispersed and uniformly grown on the surface of carbon fiber fabric;

Example 3

Step 1: Put the carbon fiber fabric into a vertical CVD furnace, heat it to 450°C for 1.5h at a heating rate of 15°C/min under a nitrogen atmosphere, remove the sizing agent on the fiber surface, and take it out after cooling to room temperature;

Step 2: the obtained carbon fiber is electrolyzed for 60s under the condition of a current intensity of 0.2A through an electrolytic cell filled with a concentration of 5% wt ammonium dihydrogen phosphate solution, followed by washing with water to remove the surface electrolyte, and drying in an oven;

Step 3: take the same molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate as the solute, and take absolute ethanol as the solvent to prepare a solution, the metal ion concentration as the catalyst is all 0.03mol/L, and the lignin salt is also the same. The concentration of the same is also 0.03mol/L, then the carbon fiber after electrolytic etching processed in step 2 is passed into the catalyst solution for 10min, and the catalyst precursor is loaded on the surface of the carbon fiber;

Step 4: The carbon fiber treated in step 3 is first reduced by a tube furnace at 450 °C, and the flow rates of H ₂ and N ₂ are both 0.5L/min. After reduction, it is then introduced into another tube furnace with a temperature of 500 ° C. To grow carbon nanotubes, the gases introduced into the furnace are N ₂ , H ₂ and C ₂ H ₂ , and the flow rates of the gases are 0.3L/min, 0.3L/min and 0.6L/min in turn. By controlling the wire running speed The reduction time and the long tube time are both 5min, and the tow is finally recovered with a wire take-up machine.

Example 4

Step 1: Put the carbon fiber fabric into a vertical CVD furnace, heat it to 450°C for 1.5h at a heating rate of 15°C/min under a nitrogen atmosphere, remove the sizing agent on the fiber surface, and take it out after cooling to room temperature;

Step 2: The obtained carbon fiber is electrolyzed for 60s under the condition of a current intensity of 0.4A through an electrolytic cell filled with a concentration of 5%wt ammonium dihydrogen phosphate solution, followed by washing with water to remove the surface electrolyte, and then drying in an oven;

Step 3: take the same molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate as the solute, and take absolute ethanol as the solvent to prepare a solution, the metal ion concentration as the catalyst is all 0.03mol/L, and the lignin salt is also the same. The concentration of the same is also 0.03mol/L, then the carbon fiber after electrolytic etching processed in step 2 is passed into the catalyst solution for 10min, and the catalyst precursor is loaded on the surface of the carbon fiber;

Step 4: The carbon fiber treated in step 3 is first reduced by a tube furnace at 450 °C, and the flow rates of H ₂ and N ₂ are both 0.5L/min. After reduction, it is then introduced into another tube furnace with a temperature of 500 ° C. To grow carbon nanotubes, the gases introduced into the furnace are N ₂ , H ₂ and C ₂ H ₂ , and the flow rates of the gases are 0.3L/min, 0.3L/min and 0.6L/min in turn. By controlling the wire running speed The reduction was made for 5 minutes, the long tube time was 10 minutes, and the tow was finally recovered with a wire take-up machine.

Example 5

Step 1: Put the carbon fiber fabric into a vertical CVD furnace, heat it to 450°C for 1.5h at a heating rate of 15°C/min under a nitrogen atmosphere, remove the sizing agent on the fiber surface, and take it out after cooling to room temperature;

Step 2: the obtained carbon fiber is electrolyzed for 80s under the condition of a current intensity of 0.3A through an electrolytic cell filled with a concentration of 5%wt ammonium dihydrogen phosphate solution, followed by washing with water to remove the surface electrolyte, and then drying in an oven;

Step 3: take the same molar ratio of ferric nitrate, nickel sulfate and sodium lignosulfonate as the solute, and take absolute ethanol as the solvent to prepare a solution, the metal ion concentration as the catalyst is all 0.03mol/L, and the lignin salt is also the same. The concentration of the same is also 0.05mol/L, then the carbon fiber after electrolytic etching processed in step 2 is passed into the catalyst solution for 10min, and the catalyst precursor is loaded on the surface of the carbon fiber;

Step 4: The carbon fiber treated in step 3 is first reduced by a tube furnace at 450 °C, and the flow rates of H ₂ and N ₂ are both 0.5L/min. After reduction, it is then introduced into another tube furnace with a temperature of 550 ° C. To grow carbon nanotubes, the gases introduced into the furnace are N ₂ , H ₂ and C ₂ H ₂ , and the flow rates of the gases are 0.3L/min, 0.3L/min and 0.6L/min in turn. By controlling the wire running speed The reduction was made for 5 minutes, the long tube time was 10 minutes, and the tow was finally recovered with a wire take-up machine.

Comparative Example 1

The difference from Example 1 is that sodium lignosulfonate is not added to the solute in step 3.

Comparative Example 2

The difference from Example 1 is that in Step 2: the obtained carbon fiber fabric is put into a hydrogen peroxide solution with a concentration of 30 wt % at 70° C. for 1.5 hours, taken out, washed and dried.

Table 1 Performance comparison table of carbon nanotube/carbon fiber fabric reinforcements prepared in this application

It can be seen from the scanning diagram that the carbon nanotubes grown by this method are obviously distributed evenly and cover the carbon fiber, and the numerical value in the monofilament tensile test also shows that because the carbon nanotubes are uniform and have a good degree of connection with the carbon fiber, so Increased strength.

Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will still Modifications may be made to the technical solutions described in the foregoing embodiments, or equivalent replacements may be made to some of them. 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. Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative work. Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (11)

1. a method using sodium lignosulfonate and bimetallic catalyst to grow carbon nanotubes on carbon fiber is characterized in that, comprising: carbon fiber desizing, electrolytic oxidation, dipping in sodium lignosulfonate and bimetallic catalyst The mixed solution of the catalyst is dried, and then carbon nanotubes are grown on the treated carbon fibers by chemical vapor deposition. 2. The method for growing carbon nanotubes on carbon fibers by using sodium lignosulfonate and a bimetallic catalyst to work together as claimed in claim 1, wherein the desizing temperature is 450-460°C for 1.5-2h . 3. the method for growing carbon nanotubes on carbon fiber by using sodium lignosulfonate and bimetallic catalyst together as claimed in claim 1, it is characterized in that, electrolyte is that concentration is 5～6%wt ammonium dihydrogen phosphate solution , the current intensity is 0.4 ~ 0.5A under the condition of electrolysis 80 ~ 90s. 4 . The method for growing carbon nanotubes on carbon fibers by using sodium lignosulfonate and a bimetallic catalyst to work together as claimed in claim 1 , wherein the bimetallic catalyst is composed of ferric nitrate and nickel sulfate. 5 . 5. the method for growing carbon nanotubes on carbon fiber using sodium lignosulfonate and bimetallic catalyst as claimed in claim 4, it is characterized in that, the mole of described ferric nitrate, nickel sulfate and sodium lignosulfonate The ratio is 1:1:1～1.5. 6. the method for growing carbon nanotubes on carbon fiber by using sodium lignosulfonate and bimetallic catalyst as claimed in claim 1, it is characterized in that, in the mixed solution of sodium lignosulfonate and bimetallic catalyst, metal The total concentration of ions is 0.01～0.05mol/L. 7 . The method for growing carbon nanotubes on carbon fibers by using sodium lignosulfonate and a bimetallic catalyst to work together as claimed in claim 1 , wherein the dipping time is 5-6 min, and the method is a wire-moving method. 8 . 8. the method for growing carbon nanotubes on carbon fiber by using sodium lignosulfonate and bimetallic catalyst to act together as claimed in claim 1, it is characterized in that, the step of described chemical vapor deposition method is: catalyst is reduced, The carbon nanotubes are re-grown, and finally the tow is recovered with a winder. 9. The method for growing carbon nanotubes on carbon fibers by using sodium lignosulfonate and a bimetallic catalyst to work together as claimed in claim 8, wherein the catalyst is reduced in a mixture of N ₂ and H ₂ , The flow rate ratio of N ₂ and H ₂ is 1:1-1.2. 10. The carbon nanotube/carbon fiber reinforcement prepared by the method of any one of claims 1-9. 11. The application of the carbon nanotube/carbon fiber reinforcement of claim 10 in the fields of aerospace, military and industry, and sporting goods, the sporting goods including rackets and clubs.

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