CN114481606B - Nickel-containing carbon nano tube/copper composite fiber and preparation method thereof - Google Patents

Abstract

The invention discloses a nickel-containing carbon nanotube/copper composite fiber and a preparation method thereof. The preparation method includes: densifying the original carbon nanotube fibers, forming a sawtooth structure on the surface of the highly densified carbon nanotube fibers while obtaining the densified carbon nanotube fibers; Nickel nanoparticles are deposited on the surface of the carbon nanotube fibers; and, using an electrochemical deposition technique, a copper layer is continuously deposited on the surface of the densified carbon nanotube fibers to obtain nickel-containing carbon nanotube/copper composite fibers. The invention utilizes the synergistic effect of densification process and nickel nanoparticles to prepare nickel-containing carbon nanotube/copper composite fiber, which can realize the improvement of comprehensive mechanical properties such as elongation, modulus and tensile strength of the composite fiber, and can also improve the composite fiber. The bonding strength of the interface; and no new substances are introduced, thereby ensuring the purification of the carbon nanotube fiber, which is conducive to the excellent performance of the carbon nanotube fiber itself.

Description

Nickel-containing carbon nanotube/copper composite fiber and preparation method thereof

technical field

The invention relates to a nickel-containing carbon nanotube/copper composite fiber and a preparation method thereof, belonging to the technical field of post-treatment of carbon nanotubes.

Background technique

In today's society, electronic and electrical equipment is used in all aspects of society. Copper has become an indispensable wire material in electronic equipment due to its relatively low price and excellent electrical conductivity (5.8×105S cm ^-1 , 25°C); at the same time, copper It also has good processability and corrosion resistance. However, the tensile strength of copper wire is low. When copper is in a hard state, its tensile strength is between 350 and 470 MPa, and the density of copper is relatively high (8.9g cm ^-3 ), which will cause copper wire In the actual service process, under the action of its own gravity, it continuously deforms, which eventually leads to the failure and fracture of the copper wire.

As a new type of conductive material, carbon nanotubes have a density of about 1 g cm ^-3 , and their theoretical strength can reach 50-200 GPa, and their mechanical properties far exceed those of copper wires. At the same time, the P orbital electrons of carbon atoms that make up carbon nanotubes can form delocalized π bonds in a wide range. The special conjugation effect of this electronic structure endows carbon nanotubes with unique electrical properties. The unique aspect ratio of the body makes carbon nanotubes have a large mean free path of electrons. Studies have shown that the mean electron free path of carbon nanotubes can exceed 30 μm (copper is 40nm), and the extremely large electron mean free path is of great significance to the improvement of the conductivity of carbon nanotubes, and its theoretical conductivity can be an order of magnitude higher than that of copper. At the same time, carbon nanotubes also have excellent characteristics such as low density, good chemical stability, high thermal conductivity, and high mechanical strength. Therefore, carbon nanotubes are one of the candidates for a new generation of high-strength and high-conductivity materials.

However, the various forms of carbon nanotubes are difficult to overcome the structural defects in the preparation process (such as more voids inside the macroscopic body, less contact area between carbon nanotubes and poor orientation of carbon nanotubes), etc. Influenced by a series of factors, the actual electrical properties of the carbon nanotube macroscopic body are far inferior to the theoretical properties; at the same time, because the grown carbon nanotube fibers often have a loose microstructure, their mechanical properties are often low. For example, the electrical conductivity of carbon nanotube fibers prepared by the floating catalytic method is usually two orders of magnitude lower than that of copper, and its electrical conductivity level is low; its mechanical properties are often around 1GPa, which is also far behind the theoretical value. In order to solve the problem of low electrical conductivity of carbon nanotube fibers, carbon nanotubes and copper are often combined, and through the play of their respective advantages, composite fibers with high strength and high conductivity are obtained. However, due to the respective atomic structure characteristics of copper atoms and carbon nanotubes, the bonding between the two is at the level of van der Waals force, resulting in low bonding strength of the "copper/carbon" interface, which seriously affects the final mechanical properties of the composite fiber.

At present, while increasing the tensile strength of composite fibers in existing technologies, the elongation is often greatly reduced, which is not conducive to the comprehensive mechanical properties of elongation, stiffness and tensile strength of composite materials.

Furthermore, the prior art often builds a strong bonding interface through the interlayer structure of "carbon nanotubes-strong bonding phase-copper" through the addition of a large amount of strong bonding mesophase. The construction of this sandwich structure often hinders the copper layer and carbon The transmission of electrons between nanotube fibers is not conducive to the electrical properties of composite fibers; moreover, after the preparation of "carbon nanotube/copper" composite materials, heat treatment is often required, and the content of alloy elements in the strong bonding phase is relatively high , these large amounts of alloying elements will inevitably diffuse during high-temperature heat treatment, which will not only reduce the promotion effect of the "strong bonding phase" on the mechanical properties of the composite fiber, but also cause alloying of the copper layer, and ultimately reduce the electrical properties of the surface copper layer .

Contents of the invention

The main purpose of the present invention is to provide a nickel-containing carbon nanotube/copper composite fiber and its preparation method to overcome the deficiencies in the prior art.

In order to realize the aforementioned object of the invention, the technical solutions adopted in the present invention include:

The embodiment of the present invention provides a kind of preparation method of nickel-containing carbon nanotube/copper composite fiber, which comprises:

Densify the original carbon nanotube fibers, and form a zigzag structure on the surface of the highly densified carbon nanotube fibers while obtaining the densified carbon nanotube fibers;

depositing nickel nanoparticles on the surface of densified carbon nanotube fibers having a zigzag structure; and,

Electrochemical deposition technology is used to continuously deposit copper layer on the surface of densified carbon nanotube fiber to obtain nickel-containing carbon nanotube/copper composite fiber.

In some embodiments, the preparation method specifically includes:

(1) first fully soaking the original carbon nanotube fiber in chlorosulfonic acid, taking it out and leaving it in the air, so that the chlorosulfonic acid and the moisture in the air fully react to generate concentrated sulfuric acid;

(2) Soak the carbon nanotube fibers obtained in step (1) in chlorosulfonic acid again at the first rate, so that the carbon nanotube fibers expand rapidly, and continue to stand still in chlorosulfonic acid until the carbon nanotubes The diameter and volume of the fibers shrink;

(3) taking out the carbon nanotube fibers obtained in step (2) from the chlorosulfuric acid at the second rate, and standing in the air so that the chlorosulfuric acid and the moisture in the air fully react to generate concentrated sulfuric acid, wherein, the first rate is greater than the second rate;

(4) Under vacuum conditions, perform high-temperature annealing treatment on the carbon nanotube fibers obtained in step (3), so that the concentrated sulfuric acid is volatilized and removed to obtain densified carbon nanotube fibers.

In some embodiments, the preparation method specifically includes:

Immerse the densified carbon nanotube fibers with a zigzag structure in a nickel salt solution for more than 24 hours, and place them in an environment with a temperature of 0°C to 20°C. The carbon nanotube fiber is immersed in hydrochloric acid for 10 minutes to 60 minutes, and then dried, so that nickel nanoparticles are deposited on the surface of the densified carbon nanotube fiber with a zigzag structure.

The embodiment of the present invention also provides the nickel-containing carbon nanotube/copper composite fiber prepared by the aforementioned method.

Compared with the prior art, the advantages of the present invention include:

1) The present invention utilizes the synergistic effect of chlorosulfonic acid densification process and nickel nanoparticles to prepare nickel-containing carbon nanotubes/copper composite fibers, which can improve the comprehensive mechanical properties of composite fibers such as elongation, modulus and tensile strength , can also improve the bonding strength of the composite interface; and, the present invention does not introduce new substances, thereby ensuring the purification of carbon nanotube fibers, which is conducive to the excellent performance of carbon nanotube fibers themselves;

2) The addition of nickel element in the preparation process of the present invention can not only promote the good deposition of copper on the surface of carbon nanotube fibers, but also directly improve the bonding strength between "C-Cu", and effectively avoid copper in the heat treatment process. The alloying of the layer can achieve the dual purpose of simultaneously improving the mechanical properties and electrical properties.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments described in the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is a process flow diagram of carrying out densification treatment to carbon nanotube fibers in a typical embodiment of the present invention;

Figure 2a is a surface topography diagram of the original carbon nanotube fiber before densification treatment in Example 1 of the present invention;

Figure 2b is a cross-sectional view of the original carbon nanotube fiber before densification treatment in Example 1 of the present invention;

Fig. 2c is a surface topography diagram of densified carbon nanotube fibers after densification treatment in Example 1 of the present invention;

Figure 2d is a cross-sectional morphology diagram of densified carbon nanotube fibers after densification treatment in Example 1 of the present invention;

Fig. 3 is the promotion effect diagram of densification treatment to the mechanical property of carbon nanotube fiber in embodiment 1 of the present invention;

Fig. 4a is the topography diagram of composite interface structure after copper plating of original carbon nanotube fibers in Example 1 of the present invention;

Figure 4b is a topography diagram of the composite interface structure of the zigzag structure carbon nanotube fibers formed after the densification treatment in Example 1 of the present invention after copper plating;

Fig. 4c is a diagram showing the influence of the original carbon nanotube fiber copper plating on the bonding force of the composite interface in Example 1 of the present invention;

Fig. 4d is a graph showing the effect of copper plating on the composite interface binding force of zigzag structure carbon nanotube fibers formed after densification treatment in Example 1 of the present invention;

Fig. 5 a is the interfacial structure topography diagram of the copper layer deposited on the surface of carbon nanotube fibers without nickel nanoparticles in Example 1 of the present invention;

Figure 5b is an interface structure topography diagram of a copper layer deposited on the surface of a carbon nanotube fiber containing nickel nanoparticles in Example 1 of the present invention;

Fig. 6a is a structural diagram of the promotion effect of the densification treatment and the synergistic effect of nickel nanoparticles on the tensile mechanical properties of carbon nanotubes/Cu composite fibers in Example 1 of the present invention;

Fig. 6b is a structural diagram of the synergistic effect of densification treatment and nickel nanoparticles on the interfacial mechanical properties of carbon nanotubes/Cu composite fibers in Example 1 of the present invention;

Fig. 7a and Fig. 7b are the fracture topography diagrams of the composite fiber after the original carbon nanotube fiber is copper-plated in the embodiment 1 of the present invention;

Fig. 7c and Fig. 7d are the fracture morphology diagrams of the composite fiber after the zigzag structure carbon nanotube fiber formed after the densification treatment in Example 1 of the present invention after copper plating;

Fig. 7e and Fig. 7f are fracture morphology diagrams of the carbon nanotube/Cu composite fiber subjected to the synergistic effect of densification treatment and nickel nanoparticles in Example 1 of the present invention.

Detailed ways

In view of the deficiencies in the prior art, the inventor of this case was able to propose the technical solution of the present invention after long-term research and a lot of practice, mainly starting from strengthening the mechanical properties of the carbon nanotube fiber body material, and utilizing the synergy of the densification process and nickel nanoparticles Effect, to improve the mechanical properties of carbon nanotube fibrils; at the same time, the design and preparation of the zigzag structure morphology was realized on the surface of the densified carbon nanotube fibers, in order to improve the combination of "carbon nanotubes/copper" composite interface Strength lays the groundwork. The technical solution, its implementation process and principle will be further explained as follows.

A method for preparing a nickel-containing carbon nanotube/copper composite fiber provided by an aspect of the embodiments of the present invention (also referred to as "a post-treatment method for improving the mechanical properties of a carbon nanotube-copper composite fiber") includes:

Densify the original carbon nanotube fibers, and form a zigzag structure on the surface of the highly densified carbon nanotube fibers while obtaining the densified carbon nanotube fibers;

depositing nickel nanoparticles on the surface of densified carbon nanotube fibers having a zigzag structure; and,

Electrochemical deposition technology is used to continuously deposit copper layer on the surface of densified carbon nanotube fiber to obtain nickel-containing carbon nanotube/copper composite fiber.

The reaction mechanism of the present invention is that: the present invention proceeds from strengthening the mechanical properties of the carbon nanotube fiber body material, and utilizes the densification process of the carbon nanotube fiber to greatly improve the mechanical properties of the carbon nanotube fiber; at the same time, The design and preparation of the zigzag structure morphology was realized on the surface of the densified carbon nanotube fiber, which laid a foundation for improving the bonding strength of the "carbon nanotube/copper" composite interface. Second: the preparation of nickel nanoparticles below 5nm was carried out on the surface of carbon nanotube fibers with zigzag structure to improve the quantity and quality of copper nucleation during electroplating. On the microscopic scale, uniform and continuous deposition of copper can be achieved on the surface of carbon nanotube fibers with a zigzag structure; on the nanoscopic scale, the "C-Ni-Cu" bonding strength can also be directly realized under the action of nickel nanoparticles improvement. The size of nickel nanoparticles on the surface of carbon nanotubes is small, some even at the atomic level, and the bonding strength of Ni-C is stronger than that of Ni-Cu, so nickel atoms are mainly distributed on the surface of carbon nanotubes during heat treatment , will not cause alloying of the copper layer, and ultimately achieve the maximum protection of the electrical properties of the copper layer.

Among them, the mechanism of forming the sawtooth structure is that after the chlorosulfonic acid molecules act on the carbon nanotubes, it will cause the redistribution of the surface charges of the carbon nanotubes, which will lead to a strong electrostatic attraction between the carbon nanotubes and the carbon nanotubes. Under the action of electrostatic attraction, the diameter of carbon nanotube fibers will be significantly reduced. When the fiber diameter is reduced, due to the different densities of the fibers in each radial direction, the degree of shrinkage of the fibers will be different, and then in Adjacent regions with different degrees of shrinkage produce aliasing.

In some embodiments, the preparation method specifically includes:

(1) first fully soaking the original carbon nanotube fiber in chlorosulfonic acid, taking it out and leaving it in the air, so that the chlorosulfonic acid and the moisture in the air fully react to generate concentrated sulfuric acid;

(2) Soak the carbon nanotube fibers obtained in step (1) in chlorosulfonic acid again at the first rate, so that the carbon nanotube fibers expand rapidly, and continue to stand still in chlorosulfonic acid until the carbon nanotubes The diameter and volume of the fibers shrink;

(3) taking out the carbon nanotube fibers obtained in step (2) from the chlorosulfuric acid at the second rate, and standing in the air so that the chlorosulfuric acid and the moisture in the air fully react to generate concentrated sulfuric acid, wherein, the first rate is greater than the second rate;

(4) Under vacuum conditions, perform high-temperature annealing treatment on the carbon nanotube fibers obtained in step (3), so that the concentrated sulfuric acid is volatilized and removed to obtain densified carbon nanotube fibers.

In some embodiments, the raw carbon nanotube fibers include carbon nanotube narrow ribbons, carbon nanotube fibers, and the like.

In some embodiments, step (1) includes: fully soaking the original carbon nanotube fiber in chlorosulfonic acid for 1-2 hours, taking it out and standing it in the air for 30-60 minutes, so that the chlorosulfonic acid and the moisture in the air generate Fully react to generate concentrated sulfuric acid. This step of the present invention skillfully utilizes the intrinsic characteristic of chlorosulfonic acid: chlorosulfonic acid is easy to infiltrate carbon nanotube fiber, but the electrostatic repulsion force that chlorosulfonic acid molecule brings is not enough to make fiber take place violent expansion; After being taken out from the chlorosulfonic acid, the chlorosulfonic acid reacts with the moisture in the air to form concentrated sulfuric acid, and the concentrated sulfuric acid has strong water absorption, which causes a large amount of water to be absorbed inside the fiber. When the fiber with a large amount of water is put into it again When the chlorosulfonic acid is inside, the moisture inside the fiber will react violently with the chlorosulfonic acid molecules to form hydrogen chloride gas. The strong air pressure causes the fiber to expand instantly, and the expanded carbon nanotube fiber is due to the electrostatic repulsion of the chlorosulfonic acid molecules. , will slowly shrink to achieve the purpose of plastic rounding, but the shrinkage is small, and further densification needs to be vacuum annealed.

In some embodiments, step (2) includes: re-immersing the carbon nanotube fibers obtained in step (1) in chlorosulfonic acid at a first rate within 3 to 5 seconds (ie, a faster rate), so that the The volume of the carbon nanotube fiber rapidly expands to 10-30 times within 1 second, and the appearance of the carbon nanotube fiber presents a cylindrical shape. The densification of carbon nanotube fibers is based on the electrostatic interaction between carbon nanotube monomers, and the cylindrical shape of the fiber will promote more carbon nanotube monomers, or more carbon nanotubes clustered in three-dimensional space. Attract each other, and then realize the close connection between carbon nanotubes and carbon nanotubes, and finally realize the densification of carbon nanotube fibers through electrostatic force. Before this step, the faster rate is used because the violent reaction between water molecules and chlorosulfonic acid is needed. If the speed is slow, the hydrogen chloride pressure generated by the reaction between water molecules and chlorosulfonic acid is not enough to cause the fiber to swell violently. Then the purpose of fiber expansion cannot be achieved, so the insertion speed must be fast enough.

In some embodiments, step (2) includes: standing the expanded carbon nanotube fibers in chlorosulfonic acid for 3 to 6 hours until the diameter and volume of the carbon nanotube fibers shrink to 20% to 30% of the expanded volume. %, the volume reduction at this time comes from the inherent van der Waals force of carbon nanotubes, and macromolecules tend to attract each other.

In some embodiments, step (3) includes: slowly taking out the carbon nanotube fibers obtained in step (2) from chlorosulfonic acid at a second rate (i.e. a slower rate), and the duration of the taking out process is more than 15 minutes , Stand in the air for 30-60 minutes to make the chlorosulfonic acid fully react with the moisture in the air to generate concentrated sulfuric acid. In this step, the carbon nanotube fibers are quite fluffy at this time, and the mechanical properties of the fluffy fibers are extremely reduced. If the removal speed is too fast, the carbon nanotube fibers will be broken.

In some embodiments, step (4) includes: keeping the carbon nanotube fibers obtained in step (3) in a tight state, and then performing high-temperature annealing treatment in a vacuum tube furnace, wherein the temperature of the high-temperature annealing treatment is 150 ℃～350℃, the degree of vacuum is 1～4×10 ^-4 Pa, and the time of high temperature annealing treatment is 15～25h.

Specifically, the present invention applies the slow volatilization process of chlorosulfonic acid and sulfuric acid under vacuum conditions, the vacuum degree is 1-4×10 ^-4 Pa, and the evaporation temperature is between 150°C and 350°C.

The densification treatment step of the present invention starts from the action mechanism of chlorosulfonic acid on carbon nanotubes, and through the development of a new process, the carbon nanotube fibers are sequentially soaked, expanded and left standing in chlorosulfonic acid, and finally realizes the densification of carbon nanotubes. The appearance and morphology of carbon nanotube fibers are changed, and the densification degree of carbon nanotube fibers is greatly improved at the same time.

The present invention is applied to the long-time protonation and short-time expansion treatment of carbon nanotube fibers in chlorosulfonic acid; the reaction of comprehensive chlorosulfonic acid and carbon nanotube fibers, the reaction of chlorosulfonic acid and moisture in the air and the carbon nanotube fibers The slow shrinkage behavior of chlorosulfonic acid realizes the change of appearance and densification of carbon nanotube fibers.

In some embodiments, the preparation method specifically includes:

Immerse the densified carbon nanotube fibers with a sawtooth structure in a nickel salt solution for more than 24 hours, and place them in an environment with a temperature of 0°C to 20°C, and then perform pyrolysis at 100°C to 1000°C after taking them out (pyrolysis After that, the nickel salt can decompose nickel atoms, and then realize the plating of nickel atoms on the surface of the carbon nanotubes; the decomposition temperature of the nickel salt is controlled at 100 ° C ~ 1000 ° C), and then the carbon nano tube fibers are immersed in hydrochloric acid for 10 minutes ~ 60min, followed by drying, so as to deposit and form nickel nanoparticles on the surface of the densified carbon nanotube fibers with a zigzag structure.

In terms of adding metals with strong binding force, the amount of nickel element added in the present invention is very small, which can not only promote the good deposition of copper on the surface of carbon nanotube fibers, but also directly improve the bonding strength between "C-Cu", and at the same time It can effectively avoid the alloying of the copper layer in the heat treatment process, and realize the dual purpose of improving the mechanical properties and electrical properties at the same time.

Further, the particle size of the nickel nanoparticles is below 5nm.

Further, the concentration of the nickel salt solution is above 0.05 mol/L, preferably 0.05 mol/L to saturation concentration.

Further, the nickel salt solution may be nickel acetate ethanol solution, but not limited thereto.

In some embodiments, the preparation method specifically includes:

Provide copper protectant solution;

Electrochemical deposition technology is used to electroplate the surface of densified carbon nanotube fibers to form a copper layer, then take it out of the electroplating solution, and place it in a copper protectant solution to fully soak for 5 seconds to 30 seconds (to ensure complete soaking) to obtain nickel-containing carbon Nanotube/copper composite fibers.

Further, the process conditions of the electrochemical deposition technology include: the output current is 0.001A-0.01A, the electroplating time is 10s-100s, and the electroplating temperature is 5°C-35°C.

Another aspect of the embodiments of the present invention also provides the nickel-containing carbon nanotube/copper composite fiber prepared by the aforementioned preparation method.

Further, the nickel element content in the nickel-containing carbon nanotube/copper composite fiber is below 0.01wt%.

Further, the thickness of the copper layer on the surface of the nickel-containing carbon nanotube/copper composite fiber is 1 μm to 10 μm.

Further, compared with the original carbon nanotube fiber, the elongation of the nickel-containing carbon nanotube/copper composite fiber is increased by 20% to 50%.

Further, the stiffness of the nickel-containing carbon nanotube/copper composite fiber is about 600MPa˜1500MPa.

Further, the tensile strength of the nickel-containing carbon nanotube/copper composite fiber is 1GPa-4GPa, and the final value reaches about 4GPa.

Further, the interface strength of the nickel-containing carbon nanotube/copper composite fiber is 15MPa-25MPa.

In summary, the present invention utilizes the synergistic effect of chlorosulfonic acid densification process and nickel nanoparticles to improve the mechanical properties of carbon nanotube fibrils. Construction, and with the help of nickel nanoparticles to promote copper deposition, the uniform and continuous coverage of the copper layer on the surface of carbon nanotube fibers was realized; finally, based on the construction of the sawtooth composite interface structure, the metal copper layer and carbon nanotube fibers were closely bonded. Occlusion, thereby improving the bonding strength of the composite interface.

The technical solutions of the present invention will be described in further detail below in conjunction with several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. For the experimental methods without specific conditions indicated in the following examples, the conventional conditions or the conditions suggested by the manufacturer are usually followed.

Example 1

Please refer to shown in Fig. 1, the specific technical steps of the preparation method of a kind of nickel-containing carbon nanotube/copper composite fiber of the present embodiment are as follows:

(1) Densification treatment of carbon nanotube fibers and preparation of serrated surface morphology

Take a carbon nanotube fiber with a length of 35-45 cm and slowly put it into a graduated cylinder filled with chlorosulfonic acid, and place it for about 1-2 hours, so that the chlorosulfonic acid can fully infiltrate the carbon nanotube fiber; then take out the carbon nanotube from the chlorosulfonic acid fiber, and stand in the air for about 30 to 60 minutes, so that the chlorosulfonic acid in the carbon nanotube fiber and the moisture in the air fully react to generate concentrated sulfuric acid; after that, within 3 to 5 seconds, at a faster rate (as far as possible) In 3 ~ 5 seconds, the fiber is completely entered in the chlorosulfonic acid solution to ensure that the reaction produces enough hydrogen chloride pressure) the carbon nanotube fiber is put back into the chlorosulfonic acid to make the fiber significantly expand in a short time (volume expand to 10 to 30 times the original size), the appearance of the fiber becomes an obvious cylindrical shape; keep the carbon nanotube fiber standing in chlorosulfonic acid for about 3 to 6 hours until the volume of the fiber shrinks significantly, as shown in Figure 1 ; Then slowly take out the carbon nanotube fibers from the chlorosulfonic acid, the whole taking out process lasts no less than 15 minutes, and put it in the air for 30-60 minutes, until the reaction between the carbon nanotube fibers and the moisture in the air is completed. Fix the above-mentioned carbon nanotube fibers on the quartz frame. During this process, keep the carbon nanotube fibers in a tight state, and then place the quartz frame in a vacuum tube furnace for high-temperature vacuum treatment; the processing temperature is between 150 ° C and The temperature is between 350°C, the degree of vacuum is 1 to 4×10 ^-4 Pa, and the treatment time is about 15 to 25 hours. Finally, the densification of carbon nanotube fibers and the preparation of the zigzag interface of carbon nanotube fibers are realized.

(2) Preparation of nickel nanoparticles on the surface of carbon nanotube fibers

Prepare a nickel acetate ethanol solution with a concentration of 0.05mol/L~saturated, and stir it magnetically for about 4 hours, then soak the densified carbon nanotube fibers in the nickel acetate ethanol solution, and place it in the refrigerator. The immersion time is controlled at more than 24 hours, and then the carbon nanotube fibers are taken out and subjected to pyrolysis at 100°C to 1000°C. After decomposition, the carbon nanotube fibers are soaked in hydrochloric acid for 10min to 60min, and then dried. Finally, the preparation of nickel nanoparticles with a particle size of less than 5 nm is realized on the surface of the carbon nanotube fiber with a zigzag structure.

(3) Electroplating of carbon nanotube fibers

The carbon nanotube fibers prepared in step (2) are fixed on the copper support, and the support carrying the carbon nanotube fibers is sealed with a resin glue gun to ensure the insulation of the support part. Adjust the output current of the electrochemical workstation to 0.001A to 0.01A, control the plating time to 10s to 100s, and configure a copper protective agent solution with a concentration of 15ml/L to 25ml/L, and adjust the indoor temperature so that the indoor temperature is between 5°C and 35°C. ℃. Afterwards, the carbon nanotube fibers are electroplated. After the electroplating, the fibers are quickly taken out from the copper solution, placed in a protective agent to fully infiltrate them, and then taken out for storage.

The inventor of this case carried out the structural characterization and performance test of the microstructure of the finally obtained nickel-containing carbon nanotube/copper composite fiber, as follows:

(1) The promotion of densification process on the mechanical properties of carbon nanotube fibers

As shown in Figure 2a and Figure 2b, the surface of the original carbon nanotube fiber is relatively smooth, and the size is large, presenting a narrow band shape. After the densification treatment, the size of the carbon nanotube fibers is significantly reduced, and more wrinkles are formed on the surface of the carbon nanotubes, as shown in Figure 2c; in its cross-sectional view, it can be observed that the wrinkles on the surface of the carbon nanotube fibers present The sawtooth morphology feature is shown in Figure 2d. Therefore, it can be concluded that after the densification treatment, the cross-sectional area of the carbon nanotube fibers is significantly reduced, and the fluffy pore structure inside the carbon nanotube fibers is also well eliminated.

Figure 3 shows the changes in mechanical properties of carbon nanotube fibers before and after densification treatment, the lower line in Figure 3 shows the tensile properties of the original carbon nanotube fibers, and the upper line shows the tensile properties of the densified fibers. Tensile data show that after densification treatment, the tensile strength, elongation and stiffness of carbon nanotube fibers have been significantly improved, that is, densification treatment can promote the mechanical properties of carbon nanotube fibers; among them, elongation Increased to 20% to 50% of the original, stiffness increased to about 210% of the original, tensile strength increased to about 400% of the original, and the final value reached about 4GPa.

(2) Influence of carbon nanotube fiber zigzag structure on "carbon nanotube/copper" composite interface

Figures 4a-4d show the structure characteristics of two composite interfaces after copper plating of original carbon nanotube fibers and carbon nanotube fibers with sawtooth interface, so as to prove the influence of the sawtooth structure formed by densification on the bonding force of the composite interface . The results show that the bonding interface between the original carbon nanotube fiber and the copper layer is relatively straight and the microstructure inside the fiber is fluffy, as shown in Figure 4a and Figure 4c, which is not conducive to the improvement of the bonding force of the composite interface; while the zigzag interface carbon nanotube The composite interface formed by the fiber and the copper layer has obvious occlusal characteristics, as shown in Figure 4b and Figure 4d, which is conducive to the improvement of the composite strength of the composite interface.

(3) Effect of nanoparticles on the copper layer deposited on the surface of carbon nanotube fibers

Figure 5a-Figure 5b shows the effect of nickel nanoparticles on the microstructure of the composite interface. When there are no nickel nanoparticles on the surface of carbon nanotube fibers, there are more gaps at the joint between the copper layer and the surface of carbon nanotube fibers, as shown in Figure 5a As shown, it shows that the bonding strength between the copper layer and the carbon nanotubes is weak; when the nickel nanoparticles are plated on the surface of the carbon nanotube fibers, the existence of voids has not been observed at the junction of the copper-carbon surface, as As shown in Figure 5b, it shows that under the action of nickel nanoparticles, the bonding force between the copper layer and the surface of carbon nanotube fibers has been significantly improved.

Figures 6a-6b show the tensile and interfacial mechanical characteristics of the composite fibers under three conditions. The results show that compared with the original copper-coated carbon nanotube fibers, the tensile mechanical properties of the composite fibers of the densified carbon nanotube fiber copper-coated and the densified carbon nanotube fiber copper-coated with nickel nanoparticles have been significantly improved. The fiber modulus, elongation and tensile strength of the latter two are significantly better than those of fibril copper-coated composite fibers, as shown in Fig. 6a. At the same time, the interfacial mechanics of composite fibers were also tested and analyzed. The results showed that the simple densification of carbon nanotube fibers did not promote the interfacial mechanics of composite fibers. However, the densification of carbon nanotubes with nickel nanoparticles The nanotube composite fiber has an obvious positive effect on the strength improvement of the "carbon nanotube/copper" composite interface, as shown in Figure 6b. In summary, the research results show that under the synergistic effect of densification treatment and nickel nanoparticles, the mechanical properties of the composite fibers can be promoted, and the tensile and interfacial mechanical properties of the composite fibers have been significantly improved.

Figures 7a-7f show the fracture morphology of the composite fibers under three conditions. The fracture microstructure of the original carbon nanotube fiber copper-plated is loose, and there are many carbon nanotube filaments, which show a certain degree of backlash. Elastic morphology, the number of carbon nanotube filaments pulled out is small, and the length is different, as shown in Figure 7a and Figure 7b; the number of carbon nanotube filaments at the fracture of the composite fiber of the densified carbon nanotube fiber copper plating significantly reduced, the rebound morphology of these filaments is significantly weakened, and the morphology characteristics of the overall fracture of the carbon nanotube fiber bundle can be observed at the fracture, as shown in Figure 7c and Figure 7d. After densification and adding nickel nanoparticles, the fracture of the copper-plated composite fiber is smooth, and the existence of carbon nanotube filaments is hardly observed, as shown in Figure 7e and Figure 7f.

In addition, the inventors of the present case also conducted experiments with reference to the foregoing examples, using other raw materials, process operations, and process conditions mentioned in this specification, and obtained satisfactory results.

Aspects, embodiments, features and examples of the present invention are to be considered illustrative in all respects and not intended to be limiting, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made without departing from the spirit and scope of the invention and that substantial, etc. Effects replace elements of the described embodiments. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is not intended that the invention be limited to the particular embodiments disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (8)

1. A preparation method of nickel-containing carbon nanotube/copper composite fiber, characterized in that, comprising: Carrying out densification treatment to the original carbon nanotube fiber, while obtaining the densification carbon nanotube fiber, a zigzag structure morphology is formed on the surface of the highly densification carbon nanotube fiber; the densification treatment specifically includes: (1) Fully soak the original carbon nanotube fibers in chlorosulfonic acid for 1-2 hours, take it out and let it stand in the air for 30-60 minutes, so that the chlorosulfonic acid can fully react with the moisture in the air to generate concentrated sulfuric acid, and Relying on the water absorption of concentrated sulfuric acid, water molecules can fully enter the interior of carbon nanotube fibers; (2) soaking the carbon nanotube fibers obtained in step (1) in chlorosulfonic acid again within 3 to 5 seconds at the first rate, so that the water inside the carbon nanotube fibers reacts with the chlorosulfonic acid molecules to generate hydrogen chloride gas, thereby causing the volume of the carbon nanotube fiber to rapidly expand to 10 to 30 times in 1 second, and the appearance of the carbon nanotube fiber presents a cylindrical shape; and the expanded carbon nanotube fiber is continued in chlorosulfonic acid Stand still for 3-6 hours until the diameter and volume of carbon nanotube fibers shrink to 20%-30% of the expanded volume; (3) Slowly take out the carbon nanotube fibers obtained in step (2) from the chlorosulfonic acid at the second speed, and the duration of the taking out process is more than 15 minutes, and stand in the air for 30-60 minutes, so that the chlorosulfonic acid and The moisture in the air fully reacts to generate concentrated sulfuric acid, wherein the first rate is greater than the second rate; (4) Under vacuum conditions, keep the carbon nanotube fibers obtained in step (3) in a tight state, and then perform high-temperature annealing treatment in a vacuum tube furnace to volatilize concentrated sulfuric acid to obtain densified carbon nanotube fibers ; Wherein, the temperature of the high temperature annealing treatment is 150 ℃ ~ 350 ℃, the degree of vacuum is 1 ~ 4 × 10 ^-4 Pa, and the time of the high temperature annealing treatment is 15 ~ 25 h; The densified carbon nanotube fibers with a sawtooth structure were immersed in a nickel salt solution for more than 24 hours, and placed in an environment with a temperature of 0 ^o C to 20 ^o C, and then pyrolyzed at 100 ° C to 1000 ° C after being taken out. Afterwards, the carbon nanotube fibers are immersed in hydrochloric acid for 10 min to 60 min, and then dried, so that nickel nanoparticles are deposited on the surface of the densified carbon nanotube fibers with a zigzag structure; and, Provide copper protectant solution; Electrochemical deposition technology is used to form a copper layer on the surface of the densified carbon nanotube fiber, and then it is taken out of the electroplating solution, and placed in a copper protectant solution to fully soak for 5 to 30 seconds to obtain a nickel-containing carbon nanotube/copper composite fiber; the process conditions of the electrochemical deposition technology include: the output current is 0.001 A~0.01 A, the electroplating time is 10 s~100 s, and the electroplating temperature is 5 ℃~35 ℃; The content of nickel in the nickel-containing carbon nanotube/copper composite fiber is below 0.01wt%; compared with the original carbon nanotube fiber, the elongation of the nickel-containing carbon nanotube/copper composite fiber is increased by 20%~ 50%, the stiffness of the nickel-containing carbon nanotube/copper composite fiber is 600 MPa~1500 MPa, the tensile strength of the nickel-containing carbon nanotube/copper composite fiber is 1 GPa~4GPa, the nickel-containing carbon nanotube The interface strength of the tube/copper composite fiber is 15 MPa~25 MPa. 2. The preparation method according to claim 1, characterized in that: the original carbon nanotube fibers are carbon nanotube narrow bands or carbon nanotube fibers. 3. The preparation method according to claim 1, characterized in that: the particle diameter of the nickel nanoparticles is below 5 nm. 4. The preparation method according to claim 1, characterized in that: the concentration of the nickel salt solution is more than 0.05 mol/L. 5. The preparation method according to claim 4, characterized in that: the concentration of the nickel salt solution is 0.05 mol/L to saturation concentration. 6. The preparation method according to claim 1, characterized in that: the nickel salt solution is nickel acetate ethanol solution. 7. The nickel-containing carbon nanotube/copper composite fiber prepared by the preparation method described in any one of claims 1-6. 8. The nickel-containing carbon nanotube/copper composite fiber according to claim 7, characterized in that: the thickness of the copper layer on the surface of the nickel-containing carbon nanotube/copper composite fiber is 1 μm-10 μm.

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