KR20170011838A

KR20170011838A - Process for preparing carbon nanotube fiber

Info

Publication number: KR20170011838A
Application number: KR1020150105189A
Authority: KR
Inventors: 오유진; 김지은; 김주한
Original assignee: 주식회사 엘지화학
Priority date: 2015-07-24
Filing date: 2015-07-24
Publication date: 2017-02-02
Also published as: KR101883034B1

Abstract

The present invention relates to a method for producing carbon nanotube fibers.

Description

PROCESS FOR PREPARING CARBON NANOTUBE FIBER [0002]

The present invention relates to a method for producing carbon nanotube fibers.

Carbon nanotubes (CNTs), a kind of carbon isotopes, have a diameter of several to several tens of nanometers and are several hundreds of micrometers to several millimeters long, reported in the journal Nature in 1991 by Dr. Iijima, Due to its physical properties and high aspect ratio, research has been conducted in various fields. The inherent properties of these carbon nanotubes are due to the sp2 bond of carbon, stronger than iron, lighter than aluminum, and exhibit electrical conductivity similar to that of metals. According to the number of nanotubes, single-wall carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-walled carbon nanotubes (Multi- Wall carbon nanotube (MWNT), and can be divided into zigzag, armchair, and chiral structures depending on the asymmetry / chirality.

Methods for fabricating carbon nanotube (CNT) fibers include forest radiation and direct radiation. The forest radiation is obtained by depositing a catalyst on a substrate, synthesizing a CNT fork in a direction perpendicular to the substrate, and pulling the CNT at the end of the substrate with a tweezers or a tape to form CNTs connected by van der Waals attraction between the CNTs It is a method to radiate CNT fiber while coming out. This method has the disadvantage that it can not increase the production amount because the continuous process is impossible.

On the other hand, carbon nanotube (CNT) fibers contain various kinds of impurities. Among them, the most abundant impurities are amorphous carbon which is decomposed in the gas phase and formed inside and outside of the fiber. These impurities must be removed because they degrade the quality of the fibers.

Accordingly, there is a method for removing amorphous carbon by passing the fibers through a heat source such as a furnace by a method of removing amorphous carbon. However, this method has a problem in that it is not economical because expensive furnaces must be used. And because of the length limitation of the furnace, there is a problem that it is uneconomical to install several furnaces in order to increase the retention time of the fibers. In another method, there is a method of lowering the moving speed of the fiber passing through the reactor, which also has a problem of lowering the productivity. Therefore, a new method for removing impurities is required.

Korean Patent No. 10-1286751

There is a problem that the apparatus for removing impurities from the carbon nanotube (CNT) fiber of the prior art is not economical. There is also a problem of lowering the productivity.

Accordingly, it is an object of the present invention to provide a carbon nanotube fiber manufacturing method which is capable of easily removing impurities and simplifying the apparatus.

In order to accomplish the above object, the present invention provides a method of manufacturing a carbon nanotube fiber, comprising: preparing a carbon nanotube fiber by reacting a spinning material with a carrier gas; applying a voltage to the carbon nanotube fiber during or after the manufacturing step; Thereby removing amorphous carbon contained in the carbon nanotube fibers. According to a preferred embodiment of the present invention, the manufacturing step comprises the steps of: (a) forming a carbon nanotube fiber by reacting a spinning material with a carrier gas; (b) winding the carbon nanotube fibers. Preferably, a step of applying a voltage to the carbon nanotube fibers may be performed between the step (a) and the step (b).

According to a preferred embodiment of the present invention, the spinning material may be a catalyst precursor dispersed in a liquid or gaseous carbon compound, and the spinning material may further include a catalytic activator. According to a preferred embodiment of the present invention, the carrier gas may be a hydrocarbon gas, an inert gas, a reducing gas or a mixture thereof.

The present invention can provide a method for manufacturing carbon nanotube fibers that can remove amorphous carbon simply by applying joule heating to carbon nanotube fibers. Further, the method of producing carbon nanotube fibers of the present invention is simple and economical.

By using the method for producing carbon nanotube fibers according to the present invention, it is possible to obtain carbon nanotube fibers from which impurities are removed and which are excellent in strength and elasticity. Accordingly, it is desired to provide a reinforcing material for a multifunctional composite material, a strain and damage sensor using a stable and repeated piezoresistance effect, a transmission line using high conductivity, a high specific surface area, an electrochemical device using excellent mechanical characteristics and electric conductivity, It is expected to be applicable to various fields such as microelectrode material, supercapacitor, actuator and the like.

FIG. 1 illustrates a method of removing amorphous carbon contained in carbon nanotube fibers according to an embodiment of the present invention. Referring to FIG.
2 is an SEM photograph of the carbon nanotube fiber of Example 1. Fig.
3 is an SEM photograph of the carbon nanotube fiber of Comparative Example 1. Fig.
4 is an SEM photograph of the carbon nanotube fiber of Comparative Example 2. Fig.

Hereinafter, the present invention will be described in detail. The following detailed description is merely an example of the present invention, and therefore, the present invention is not limited thereto.

In the drawings, like reference numerals are used for similar elements.

The term "and / or" includes any one or a combination of the plurality of listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it is to be understood that other elements may be directly connected or connected, or intervening elements may be present.

The singular expressions include plural expressions unless otherwise specified.

The terms "comprises", "having", or "having" mean that there is a feature, a value, a step, an operation, an element, a component or a combination thereof described in the specification, Does not exclude the possibility that a number, a step, an operation, an element, a component, or a combination thereof may be present or added.

The term "carbon nanotube fibers" in the present specification refers to both carbon nanotubes grown in a fiber form or formed by fusing a plurality of carbon nanotubes in a fiber form.

Techniques for producing carbon nanotube fibers include solution spinning, array spinning, aerogel spinning and / or film twisting or rolling. The present invention follows a process of directly spinning carbon nanotube fibers or ribbons from a carbon nanotube aerogel formed immediately after the introduction of a spinning material in a reactor by using chemical vapor deposition (CVD).

In the direct spinning, carbon nanotubes are synthesized in a heating furnace by injecting carbon nanotubes at a constant rate in a vertical furnace together with a carrier gas by adding a catalyst to the carbon nanotubes, and pure carbon nanotubes Carbon nanotube fibers are continuously produced.

The catalyst precursor of the present invention is a substance which is not contained in the catalyst cycle but is changed into an active catalyst (or produces an active catalyst) in the course of the catalytic reaction, and in the present invention, the catalyst precursor forms a catalyst Then, CNT is synthesized.

In the conventional method of manufacturing carbon nanotube (CNT) fibers, there is a method of passing impurities through a heat source such as a furnace to remove impurities. However, this method has a problem in that it is not economical because a costly furnace must be used have.

Accordingly, the present inventors made an effort to solve this problem by finding a method of manufacturing carbon nanotube fibers using Joule heating.

The method includes the steps of: preparing a carbon nanotube fiber by reacting a spinning material with a carrier gas; and applying a voltage to the carbon nanotube fiber during or after the manufacturing step, And removing amorphous carbon contained in the fiber.

Hereinafter, the present invention will be described more specifically with reference to the drawings.

According to a preferred embodiment of the present invention, the manufacturing step comprises the steps of: (a) forming a carbon nanotube fiber by reacting a spinning material with a carrier gas; (b) winding the carbon nanotube fibers. More specifically, when the spinning material and the carrier gas are continuously reacted, carbon nanotubes are synthesized. Then, the synthesized carbon nanotubes are successively gathered by growing or fusing, and cylindrical carbon nanotube fibers are formed. Then, the formed carbon nanotube fibers are wound using a winding means. At this time, the carbon nanotube fibers include amorphous carbon. Therefore, a voltage is applied to the carbon nanotube fibers during or after the step of manufacturing to remove amorphous carbon. Preferably, the carbon nanotube fibers are wound while the voltage is applied in the step (b). Most preferably, a step of applying a voltage to the carbon nanotube fibers between the step (a) and the step (b) may be performed.

The emissive material may comprise carbon compounds in gaseous form as well as in liquid form. The liquid or gaseous carbon compound diffuses as a carbon source as a catalyst and is synthesized into carbon nanotubes. The molecular weight distribution, concentration, viscosity, surface tension, dielectric constant and properties of the solvent to be used are taken into consideration.

According to a preferred embodiment of the present invention, the liquid or gaseous carbon compound is selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, vinyl acetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, And one or more selected from the group consisting of polyethylene glycol, ethyl formate, mesitylene, tetrahydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride and pentane. Specifically, the liquid carbon compound may be at least one selected from the group consisting of ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetate, diethyl ether, polyethylene glycol, ethyl formate, mesitylene, tetrahydrofuran And may include one or more selected from the group consisting of formamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride, and pentane. (C ₂ H ₅ OH), xylene (C ₈ H ₁₀ ), diethyl ether [(C ₂ H ₅ ) ₂ _O ], polyethylene glycol [(CH ₂ -CH ₂ -O) ₉ ] 1-propanol _{(CH 3 CH 2 CH 2 OH} ), acetone (CH ₃ OCH _3), ethyl formate (CH ₃ CH ₂ COOH), benzene (C ₆ H _6), hexane (C ₆ H ₁₄₎ and mesitylene [C ₆ H ₃ (CH ₃ ) ₃ ]. The gas-phase carbon compound may include at least one selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, and vinyl acetylene.

According to a preferred embodiment of the present invention, the spinning material may be a catalyst precursor dispersed in a liquid or gaseous carbon compound. The spinning material may be mixed with 0.5 to 5 wt%, preferably 1 to 5 wt%, or 1.5 to 4 wt% of the catalyst precursor to the liquid or gaseous carbon compound. If excess catalyst precursor is used in comparison with the liquid or gaseous carbon compound of the spinning material, the catalyst acts as an impurity and it is difficult to obtain high purity carbon nanotube fibers. It may also be a factor that hinders the thermal, electrical and / or physical properties of the carbon nanotube fibers. In the present invention, the catalyst precursor may include at least one selected from the group consisting of metallocene including ferrocene, iron, nickel, cobalt, platinum, ruthenium, molybdenum, vanadium and oxides thereof, no. The catalyst precursor may also be in the form of nanoparticles. And preferably in a metallocene form such as ferrocene, which is a compound containing iron, nickel, cobalt and the like; Iron such as iron chloride (FeCl ₂ ); cobalt; And a nickel atom may be used as the catalyst precursor.

According to a preferred embodiment of the present invention, the spinning material may further include a catalytic activator. Generally, carbon nanotubes are synthesized by diffusion of carbon into the catalyst in the molten state of the catalyst, followed by precipitation of the carbon nanotubes. The catalyst activator is used as a promoter in the synthesis of carbon nanotubes to increase the carbon diffusion rate, Thereby synthesizing carbon nanotubes. As the catalytic activator, thiophene (C ₄ H ₄ S) may be used. Thiophene reduces the melting point of the catalyst and removes the amorphous carbon, allowing synthesis of high purity carbon nanotubes at low temperatures. The content of the catalytic activator may also affect the structure of the carbon nanotubes. For example, when 1 to 5% by weight of thiophene is mixed with ethanol as the carbon compound, multiwall carbon nanotube fibers are obtained And when the thiophene is mixed with ethanol in an amount of 0.5% by weight or less, single-walled carbon nanotube fibers can be obtained. According to a preferred embodiment of the present invention, the catalyst precursor and the catalytic activator may be liquid in the liquid carbon compound, and may be vapor in the vapor carbon compound. Therefore, the liquid carbon compound can be injected by dissolving the catalyst precursor or the catalytic activator, and vaporized into the gas-phase carbon compound to be injected into the gas form.

Further, the carrier gas may be a hydrocarbon gas, an inert gas, a reducing gas, or a mixed gas thereof. The inert gas may be argon, nitrogen, or a mixed gas thereof, and the reducing gas may be hydrogen, ammonia, or a mixed gas thereof.

According to a preferred embodiment of the present invention, the reaction temperature of the producing step may be 1,000 to 3,000 ° C. Preferably 1,000 to 2,000 deg. C, 1,000 to 1,500 deg. C, or 1,000 to 1,300 deg. C, and more preferably 1,100 to 1,200 deg. If it is less than 1000 ° C, carbon nanotube fibers may not be formed. If the temperature is higher than 3000 ° C, carbon nanotubes may be vaporized. Therefore, the above range is preferable.

The carbon nanotube fiber is an aggregate formed of carbon nanotubes, and the step of collecting and winding the carbon nanotube fiber is performed. By applying voltage during or after this step, line heating is generated. As a result, the amorphous carbon, which is an impurity contained in the carbon nanotube and / or the carbon nanotube fiber, is removed.

That is, the present invention applies a voltage to both ends of carbon nanotube fibers including amorphous carbon, thereby generating joule heating in the fibers themselves. At this time, the amorphous carbon may be removed from the carbon nanotube fibers by Joule heating.

Meanwhile, the amorphous carbon can be oxidized and removed at a temperature of 300 to 500 ° C, preferably 400 to 500 ° C. Thus, the voltage may be between 1 and 15 volts, and preferably between 8 and 11 volts. If it is less than 1 V, there may be a problem that the amorphous carbon is not removed, and when it exceeds 11 V, carbon nanotube fibers may be oxidized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a step of applying a voltage to a carbon nanotube fiber according to a preferred embodiment of the present invention. FIG. Specifically, carbon nanotube fibers are fixed to a certain length by two guides such as a copper electrode. By applying a voltage to the guide, joule heating of 300 to 500 ° C is generated on the carbon nanotube fibers to remove impurities such as amorphous carbon. Or for continuous reaction, the carbon nanotube fibers can be slidly moved to the guide and a voltage can be applied at the same time.

According to a preferred embodiment of the present invention, the carbon nanotube fibers from which the amorphous carbon has been removed may be wound. The winding speed affects the orientation of the carbon nanotubes in the fibers in the fiber axis direction, thereby determining the thermal, electrical, and physical properties of the carbon nanotube fibers. Preferably, it can be wound in the range of 5 to 100 rpm.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Changes and modifications may fall within the scope of the appended claims.

Example One

A spinning solution was prepared by mixing 1.6% by weight of the ferrocene catalyst precursor and 0.8% by weight of thiophene in 97.6% by weight of the acetone liquid carbon compound. And we prepared the hydrogen carrier. The spinning solution was introduced at the rate of 10 ml / hr and the carrier gas was fed at the rate of 2 L / min to the top of the cylindrical reactor at a temperature of 1173 ° C. The carbon nanotube fibers discharged to the discharge port at the bottom of the reactor were wound with a winding means composed of two bobbins. Two copper electrodes were provided between the two bobbins, and a voltage was connected to the copper electrode. Then, a voltage of 10 V was applied to both ends of the carbon nanotube fiber, and a 480 ° C. line heating was generated.

Comparative Example One

The same procedure as in Example 1 was carried out except that no voltage was applied.

Comparative Example 2

Except that a voltage of 16 V was applied.

Experimental Example One

SEM-EDS of the carbon nanotube fibers prepared in Example 1, Comparative Example 1 and Comparative Example 2 was measured and shown in Table 1 and Figs. 2 to 4.

division Example 1 Comparative Example 1 Comparative Example 2 Element Weight Atomic Weight Atomic Weight Atomic C 64.00 81.53 69.45 85.50 11.63 24.40 O 12.92 12.36 9.54 8.81 31.70 50.00 Fe 23.08 6.11 0.57 0.29 56.67 25.60 S - - 20.44 5.40 - - Totals 100.00 100.00 100.00 100.00 100.00 100.00

Fig. 2 is a SEM photograph of Example 1, Fig. 3 is Comparative Example 1, and Fig. 4 is Comparative Example 2. Fig.

Specifically, referring to the drawings and Table 1, in Example 1, the temperature of the CNT fiber is maintained at 480 DEG C to remove amorphous carbon, and the highly crystalline CNT remains without being removed. It was also observed that iron oxide, which is an impurity of iron catalyst, remained on the CNT surface. Therefore, it can be seen that the amorphous carbon-removed carbon nanotube fiber was finally wound in Example 1.

Comparative Example 1 showed that sulfur (S) remained in the non-oxidized thiophene catalyst as a result of EDS analysis. It can be seen that iron oxide, which is an impurity of amorphous carbon and iron catalyst, remains on the surface of the CNT fiber. This is because the amount of carbon was relatively large because amorphous carbon was not removed. Therefore, although the amount of iron oxide seems to remain small, it can be seen that impurities are much larger in conclusion.

In Comparative Example 2, the temperature of the CNT fiber was 700 ° C. or higher, and the amorphous carbon as well as the crystalline carbon material CNT were oxidized and removed. Looking at the remaining fibers, there is red matter like iron oxide, which can be estimated from SEM photographs and EDS analysis. Most CNTs are oxidized, but some CNTs are observed.

Claims

And reacting the spinning gas with the carrier material to produce carbon nanotube fibers,
And applying a voltage to the carbon nanotube fibers during or after the step of fabricating the carbon nanotube fibers to remove amorphous carbon contained in the carbon nanotube fibers.

The method according to claim 1,
Wherein the voltage is between 1 and 15 volts.

The method according to claim 1,
The manufacturing step
(a) reacting a spinning gas with a carrier gas to form carbon nanotube fibers; And
and (b) winding the carbon nanotube fibers.

The method of claim 3,
Between the step (a) and the step (b)
And applying a voltage to the carbon nanotube fibers.

The method according to claim 1,
Wherein the reaction temperature of the step of preparing the carbon nanotube fiber is 1,000 to 3,000 ° C.

The method according to claim 1,
Wherein the spinning material comprises a catalyst precursor dispersed in a liquid or gaseous carbon compound.

The method of claim 6,
The liquid or gaseous carbon compound may be at least one selected from the group consisting of methane, ethylene, acetylene, methyl acetylene, vinyl acetylene, ethanol, methanol, propanol, acetone, xylene, chloroform, ethyl acetic acid, diethyl ether, polyethylene glycol, Wherein the carbon nanotube fiber comprises at least one selected from the group consisting of tetrahydrofuran (THF), dimethylformamide (DMF), dichloromethane, hexane, benzene, carbon tetrachloride and pentane.

Claim 6
Wherein the catalyst precursor comprises at least one selected from the group consisting of metallocene including ferrocene, iron, nickel, cobalt, platinum, ruthenium, molybdenum, vanadium and oxides thereof.

The method of claim 6,
Wherein the spinning material further comprises a catalytic activator.

The method of claim 6 or claim 9,
The catalyst precursor and the catalytic activator are liquid in the liquid carbon compound,
And the carbon compound is in a gaseous phase.

The method according to claim 1,
Wherein the carrier gas is a hydrocarbon gas, an inert gas, a reducing gas, or a mixed gas thereof.

The method of claim 11,
Wherein the inert gas is argon, nitrogen or a mixed gas thereof,
Wherein the reducing gas is hydrogen, ammonia, or a mixed gas thereof.