JP2013047163A - Carbon nanotube yarn and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon nanotube yarn, and to provide a method of producing the same which can achieve the carbon nanotube yarn that can achieve high electric conductivity and that causes little degradation in properties such as flexibility.SOLUTION: The CNT (carbon nanotube) yarn 5 is configured such that a lot of grown CNTs 11 are formed among base CNTs 3, the base materials arranged in parallel to be bundled, so that the base CNTs 3 are electrically connected. Spaces formed among the base CNTs 3 are filled with the grown CNTs 11 to some extent. Specifically there are the smaller number of spaces among the base CNTs 3 in the case of the CNT yarn 5 having the grown CNTs 11 than in the case of the CNT yarn 5 having no grown CNT 11, whereby the electric conductivity of the CNT yarn 5 is improved by the electrical connection between the CNT 5 and the grown CNTs 11.

Description

  The present invention relates to a carbon nanotube thread formed from, for example, a large number of carbon nanotubes and a method for producing the same.

  Conventionally, carbon nanotubes (hereinafter sometimes referred to as CNT) which are one of carbon-based microstructures are known. This CNT is, for example, a pipe-like carbon material having a diameter of about 0.5 nm to 10 nm and a length of about 1 μm.

  Since CNT has a fine structure as described above, handling and workability are poor as it is. For this reason, it has been attempted to produce an aggregate of CNTs that can be easily handled while being confirmed with the naked eye.

Examples of the CNT aggregate include a CNT yarn in which a large number of CNTs are formed into a thread (for example, a CNT twisted yarn obtained by twisting CNTs: CNT yarn).
The CNT yarn described above can be manufactured as follows.

  First, a plurality of CNTs oriented in a direction perpendicular to the substrate are formed on the substrate. Then, a CNT yarn can be manufactured by sequentially drawing and spinning a bundle of CNTs from the substrate (see Patent Document 1). On the other hand, a method of forming CNT yarns directly from a furnace for synthesizing CNTs has also been devised (see Patent Document 2).

  By the way, the CNT yarn produced by the above-described technique has many hollow portions (for example, about 50% hollow portions) among a large number of CNTs, and therefore has a problem that electric conductivity is smaller than that of a single CNT. was there.

For example, in the case of CNT alone, the electric conductivity is 10 ⁶ to 10 ⁸ [S · m ⁻¹ ], but in the case of CNT yarn, the electric conductivity is about 10 ⁴ [S · m ⁻¹ ]. It is.
As a countermeasure, a technique for increasing electrical conductivity of CNT yarn by post-treatment such as chemical treatment, doping, or intercalation is disclosed (see Non-Patent Documents 1 and 2).

JP 2011-138703 A Special table 2007-536434 gazette

Lee, R.S.; Kim, H.J.; Fischer, J.E.; Thess, A. & Smalley, R.E., Conductivity enhancement in single-walled carbon nanotube boundles doped with K and Br, Nature, 1997,388,255 Duclaux, L., Review of the doping of carbon nanotubes (multiwalled and single-walled), Carbon, 2002, 40, 1751-1764

However, even when the electrical conductivity is increased by the above-described post-processing technique, the electrical conductivity only increases to about 10 ⁵ [S · m ⁻¹ ], which is not always sufficient.
Further, depending on the post-treatment, for example, by adding a substance other than CNT to the CNT yarn, the properties (for example, flexibility) of the CNT yarn may be affected. In this case, the properties of the CNT yarn are deteriorated. There was also a problem.

  The present invention has been made in view of the above points, and provides a carbon nanotube yarn that can realize a carbon nanotube yarn that can achieve higher electrical conductivity than the conventional one and that has less deterioration in properties such as flexibility, and a method for producing the same. For the purpose.

  (1) The invention of claim 1 is a carbon nanotube yarn comprising a plurality of carbon nanotubes constituting a base material, wherein each base material is disposed in a space between the carbon nanotubes of each base material constituting the carbon nanotube yarn. The carbon nanotubes are grown from the carbon nanotubes of the respective substrates so that the carbon nanotubes are electrically connected to each other.

  The CNT yarn of the present invention grew from each base material CNT so as to electrically connect the base materials CNT to each other in a space between the base materials CNT (hereinafter also referred to as base material CNT). CNT (hereinafter also referred to as “growth CNT”).

That is, in this invention, each base material CNT is electrically connected when the growth CNT (growth between base materials) contacts.
This greatly improves the electrical conductivity of the CNT yarn. Also, this improvement in electrical conductivity is not due to the contact of grown CNTs (of the same material), but not due to the addition of other different substances, thus suppressing degradation of properties such as flexibility of the CNT yarn. Can do.

  (2) The invention of claim 2 is a method of producing a carbon nanotube yarn comprising a plurality of carbon nanotubes constituting a base material, and a new carbon nanotube yarn is formed on each of the base materials constituting the carbon nanotube yarn. A first step of supporting a catalyst for growing carbon nanotubes, a step of growing the new carbon nanotubes starting from the catalyst, and electrically connecting the carbon nanotubes of the substrates by the new carbon nanotubes. And two steps.

  In the CNT yarn manufacturing method of the present invention, a catalyst for growing a new CNT is supported on each substrate CNT in the first step, and a new CNT is grown from the catalyst in the second step. Thus, the base materials CNT are electrically connected to each other.

  That is, in the present invention, the CNTs are newly grown inside the CNT yarn and the grown CNTs are newly brought into contact with the base CNTs, thereby electrically connecting the base CNTs.

  This greatly improves the electrical conductivity of the CNT yarn. Further, since the improvement in electrical conductivity is not due to the addition of other different substances but due to the contact of the grown CNTs, it is possible to suppress deterioration of properties such as flexibility of the CNT yarn.

(3) The invention of claim 3 is characterized in that the catalyst is supported after the carbon nanotube yarn is subjected to post-treatment by annealing.
In the present invention, since the catalyst is supported after the CNT yarn is annealed (that is, the temperature is gradually lowered after heating), there is an advantage that the wettability of the catalyst (specifically, the solution containing the catalyst) is good. Thereby, a catalyst can be reliably carry | supported with respect to base material CNT.

In addition, as a heating temperature in annealing treatment, the range of 600-3000 degreeC is employable.
(4) The invention of claim 4 is characterized in that the catalyst is supported after the carbon nanotube yarn is subjected to post-treatment with ultraviolet rays.

  In the present invention, since the catalyst is loaded after the CNT yarn is irradiated with ultraviolet rays, there is an advantage that the wettability of the catalyst (specifically, the solution containing the catalyst) is good. Thereby, a catalyst can be reliably carry | supported with respect to base material CNT.

(5) The invention of claim 5 is characterized in that the catalyst is supported after the carbon nanotube yarn is subjected to a post-treatment by plasma.
In the present invention, since the catalyst is supported after the CNT yarn is placed in an environment where plasma is generated, there is an advantage that the wettability of the catalyst (specifically, a solution containing the catalyst) is good. Thereby, a catalyst can be reliably carry | supported with respect to base material CNT.

(6) The invention of claim 6 is characterized in that the catalyst is supported on the carbon nanotube yarn by dip coating (immersion).
The present invention exemplifies a catalyst loading method. Thereby, the catalyst can be easily supported on the CNT yarn.

(7) The invention of claim 7 is characterized in that the catalyst is supported on the carbon nanotube yarn by sputtering.
The present invention exemplifies a catalyst loading method. Thereby, the catalyst can be easily supported on the CNT yarn.

  Various methods such as well-known chemical vapor deposition (CVD) and laser ablation can be employed as a method for growing CNT from the CNT yarn.

It is explanatory drawing which shows the method of producing CNT thread | yarn from CNT. It is a front view which shows the CNT thread | yarn formed from CNT. It is explanatory drawing which shows the procedure which manufactures CNT yarn. It is explanatory drawing which shows the process which grows CNT newly in a CNT thread | yarn. It is explanatory drawing which expands and shows the structure of CNT yarn. (A) is explanatory drawing which shows typically the connection state of base material CNT and growth CNT, (b) is explanatory drawing which illustrates the state of resistance in the connection state of base material CNT and growth CNT. It is a graph which shows the relationship between the resistance value of CNT thread | yarn, and the number of connection points (base CNT and growth CNT). (A) is explanatory drawing which shows typically the connection state of base material CNT in the conventional CNT thread | yarn which does not have growth CNT, (b) is explanatory drawing which illustrates the state of resistance in the connection state of base material CNT.

  Embodiments of the present invention will be described based on examples.

In this embodiment, a CNT yarn that is a twisted yarn and a manufacturing method thereof will be described.
a) First, a method for producing the CNT yarn of this example will be described.
(1) Manufacture of CNT yarn Length: 8 mm x width: 2 mm x thickness: 1 mm of Si substrate (area: 16 mm ² ), 0.002 mol of iron (Fe) per 1 m ² was deposited by vacuum deposition. An active Si substrate was obtained.

  This active Si substrate is placed in an electric furnace constituting a CVD apparatus, heated to 700 ° C., ethylene gas at 30 cc / min, hydrogen gas at 70 cc / min, and argon gas at 400 cc / min for 5 minutes. Circulated.

As a result, as shown in FIG. 1, an alignment film (matrix) of CNTs in which a large number of CNTs were deposited was formed on the Si substrate 1.
One end of the deposited CNT is fixed to the Si substrate 1 and is uniformly oriented in a direction perpendicular to the Si substrate 1. The diameter of each CNT is about 10 nm, and the length of the CNT is about 300 μm.

Next, in the alignment film of CNTs aligned on the Si substrate 1, the end of a bundle made of a plurality of CNTs was picked with an extraction tool, and extracted in a direction perpendicular to the alignment direction of the CNTs.
The end of the drawn CNT bundle (the rear end with respect to the drawing direction) and the end of the adjacent CNT bundle on the Si substrate 1 are connected by van der Waals force. As a result, the CNT bundle Is connected stably for a long time.

  At this time, a bundle of CNTs was drawn out from a CNT alignment film aligned on the Si substrate 1 at a plurality of locations. Then, by twisting a plurality of CNT bundles, as shown in FIG. 2, CNT yarn (CNT twisted yarn) 5 composed of CNT (base material CNT) 3 serving as a base material was obtained.

(2) Post treatment of CNT yarn Next, annealing treatment (natural cooling treatment after heating) was performed on the CNT yarn 5 produced in (1) above for the purpose of improving the wettability of the catalyst.

Specifically, as shown in FIG. 3, the CNT yarn 5 was put in a heating container 7, heated in a vacuum state at 900 ° C. for 30 minutes, and then naturally cooled to room temperature.
Next, the annealed CNT yarn 5 is dipped in a solution (catalyst solution) containing a catalyst, and the catalyst solution is attached to the entire CNT yarn 5.

Examples of the catalyst solution include a solution of iron (II) acetate using alcohol (for example, ethanol) as a solvent. In this case, iron acts as a catalyst.
Next, the catalyst solution adhered to the CNT yarn 5 is dried, and the catalyst is supported on the surface or inside of the CNT yarn 5 (specifically, the surface of each CNT).

Next, the dried CNT yarn 5 is put into the electric furnace 9 of the CVD apparatus used when growing the CNT, and the CNT is grown by well-known CVD.
Specifically, as shown in FIG. 4, for example, the temperature in the electric furnace 9 is gradually increased at a predetermined temperature increase rate, and Ar / H ₂ gas is supplied into the electric furnace 9 to form a catalyst. Fe was produced. Ar / H ₂ gas was supplied at a flow rate of 130 cc / min.

When the temperature in the electric furnace 9 reached 880 ° C., the supply of Ar / H ₂ gas was stopped.
Further, ethylene gas was supplied at a flow rate of 20 cc / min for 10 minutes after the temperature in the electric furnace 9 reached 880 ° C. At this time, heating of the electric furnace 9 was also stopped.

Thereby, the CNT yarn 5 (including CNT grown by the post-treatment) of this example was obtained.
b) Next, the structure of the CNT yarn 5 of this embodiment will be described.

  As schematically shown in FIG. 5, the CNT yarn 5 of this example is arranged between the base materials CNT 3 between the CNTs (base materials CNT) 3 constituting a large number of base materials arranged in parallel and bundled. A large number of CNTs (growth CNTs) 11 (indicated by gray portions) are formed so as to be in contact with each other.

  The grown CNT 11 fills the space between the base materials CNT 3 to some extent. For example, in the case of the CNT yarn 5 of the present embodiment, the space between the base materials CNT3 is smaller than when there is no growth CNT11.

  Further, the electrical conductivity of the CNT yarn 5 of this example is about 20% compared to the case where there is no growth CNT 11 because each growth CNT 11 is electrically connected to each base material CNT 3. It has improved.

c) Next, the function and effect of this embodiment will be described.
As schematically illustrated in FIG. 6A, in the CNT yarn 5 of this example, the base materials CNT3 (shown by the solid line in the figure) are electrically connected to each other at the connection points (shown by the white circles in the figure). However, not only that, but also by the grown CNTs 11 (shown by broken lines in the figure), they are electrically connected.

  That is, the growth CNT 11 is in contact with the base material CNT 3 by a new connection point (indicated by a gray circle in the figure), whereby the base material CNT 3 is electrically connected. That is, the growth CNT 11 is connected in parallel to the base material CNT3, for example.

  Further, as shown in a circuit diagram of a part of the CNT yarn 5 in FIG. 6B, the grown CNTs 11 are connected to the plurality of base materials CNT3 so as to be connected in parallel, for example. In addition, the white part of the figure shows the resistance (connection resistance) of the connection part between the base materials CNT3, and the gray part shows the resistance (connection resistance) between the base material CNT3 and the growth CNT11. Here, since the resistance of the connection portion is larger than the CNT itself, only the resistance of the connection portion is shown.

In this way, by forming a parallel circuit with the grown CNTs 11, the total resistance of the circuit is lowered, thereby improving the electrical conductivity of the CNT yarn 5.
For example, as shown in the figure, when resistors are connected (having respective resistance values 2R and R), the total resistance value is reduced to R.

  This is because, as shown in FIG. 7, the total resistance decreases as the number of connection points increases, as shown by the total resistance and the number of connection points (connected in parallel). In addition, this FIG. 7 is the relationship between the number of connection points and the total resistance of the circuit when a wire having a predetermined resistance value is connected to a pair of parallel wires each having a predetermined resistance value. Is shown.

  On the other hand, as schematically illustrated in FIG. 8 (a), the conventional CNT yarns do not have grown CNTs as in this example, and therefore the base materials CNT3 (shown by the solid line in FIG. 8) Are merely electrically connected at each connection point (indicated by white circles in the figure).

  As shown in the circuit diagram of FIG. 8B in this state, conventionally, the resistance (connection resistance: for example, each resistance value R) of the connection portion of each base material CNT is arranged in series. Resistance (for example, 3R) increases.

  As described above, in the present embodiment, the growth CNTs 11 grown from the respective base materials CNT3 are provided in the spaces between the respective base materials CNT3 so as to electrically connect the respective base materials CNT3 to each other. The electrical conductivity of the CNT yarn 5 is greatly improved. In addition, since the improvement in electrical conductivity is not due to the addition of other different substances but due to the contact of the grown CNTs 11, it is possible to suppress deterioration of characteristics such as flexibility of the CNT yarn 5.

  In this embodiment, since the annealing treatment is performed as a post-treatment before the growth CNT 11 is formed, the wettability of the catalyst solution with respect to the base material CNT3 is good, and the catalyst is suitably supported on the surface of the base material CNT3. can do.

Needless to say, the present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the scope of the present invention.
(1) For example, in the above-described embodiment, the CNT yarn is annealed as a post treatment, but the CNT yarn may be irradiated with ultraviolet rays separately. This also improves the wettability of the catalyst solution.

(2) Further, as another post-treatment, the CNT yarn may be in an environment where plasma is generated. This also improves the wettability of the catalyst solution.
(3) Further, in the above embodiment, the catalyst is supported by immersing the CNT yarn in the catalyst solution. However, the catalyst may be supported by sputtering.

1. Si substrate 3. Base material carbon nanotube (CNT)
5. Carbon nanotube yarn (CNT yarn)
11. Grow carbon nanotubes (growth CNT)

Claims (7)

In the carbon nanotube yarn comprising a plurality of carbon nanotubes constituting the substrate,
Carbon nanotubes grown from the carbon nanotubes of the respective base materials are electrically connected to the spaces between the carbon nanotubes of the respective base materials constituting the carbon nanotube yarn. A carbon nanotube yarn characterized by having. A method for producing a carbon nanotube yarn comprising a plurality of carbon nanotubes constituting a substrate,
A first step of supporting a catalyst for growing a new carbon nanotube on the carbon nanotube of each of the base materials constituting the carbon nanotube yarn;
A second step of growing the new carbon nanotubes starting from the catalyst, and electrically connecting the carbon nanotubes of the base materials to each other by the new carbon nanotubes;
A method for producing a carbon nanotube yarn, comprising:   The method for producing a carbon nanotube yarn according to claim 2, wherein the catalyst is supported after the carbon nanotube yarn is subjected to post-treatment by annealing.   The method for producing a carbon nanotube yarn according to claim 2, wherein the catalyst is supported after the carbon nanotube yarn is subjected to a post-treatment with ultraviolet rays.   The method for producing a carbon nanotube yarn according to claim 2, wherein the catalyst is supported after the carbon nanotube yarn is subjected to a post-treatment by plasma.   The method for producing a carbon nanotube yarn according to any one of claims 2 to 5, wherein the catalyst is supported on the carbon nanotube yarn by dip coating.   The method for producing a carbon nanotube yarn according to any one of claims 2 to 5, wherein the catalyst is supported on the carbon nanotube yarn by sputtering.