JP2009023881A - Carbon nanotube and carbon nanotube structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structurally stable carbon nanotube bundle and a carbon nanotube structure capable of increasing the surface area without carrying out an opening treatment. <P>SOLUTION: In the carbon nanotube bundle obtained by bundling a plurality number of the carbon nanotubes, the structure of the bundle and the number of the carbon nanotubes forming the bundle are fixed so that a circle A satisfying relational expressions (1) S1<S2 ...(1) and L1>2×L2 ...(2) is present. In the expression, S1 expresses the area of the cut section when the bundle is cut with a plane vertical to the axial direction of the bundle, L1 expresses the outer peripheral length of the cut section, S2 expresses the area of the circle A and L2 expresses the circumferential length of the circle A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbon nanotube bundle having a large surface area and structurally stable, and a structure using the same.

  Carbon Nanotube (hereinafter sometimes abbreviated as CNT) is a hollow material having a structure in which graphene sheets in which carbon atoms are arranged in a hexagonal network are rolled into a cylindrical shape, and has a high surface area and extremely strong mechanical properties. Applications in various fields are expected due to its properties and excellent electronic properties.

As described above, since CNT is a hollow substance, when gas or ions are adsorbed, it is theoretically possible to use the inside as an adsorption site. For example, in a single-walled CNT, the internal and external surface areas can be combined to obtain a large specific surface area of 2600 to 3000 m ² / g (half the surface if it is a single surface) (the specific surface area is slightly different depending on the C—C bond distance). ). Research and development for adsorbing gases such as hydrogen, electrolyte ions, and the like using this large specific surface area are being conducted (see, for example, Patent Documents 1 to 3). In particular, in the past, research and development that use the inside of CNTs as an adsorption site by utilizing the property of being hollow have been actively conducted.

  In addition, research and development of brush-like CNTs that are vertically aligned on a substrate have been actively conducted. Since brush-like CNTs aligned perpendicularly to the substrate can increase the surface area of the CNT in the substrate unit area, the efficiency of adsorbing gas, ions, and the like can be increased. As a method for synthesizing brush-like CNTs, a chemical vapor deposition (CVD) method that can directly synthesize CNTs on a substrate is often used.

  When CNT having a large specific surface area is used as a substance to be adsorbed, the relationship between the CNT diameter and CNT interval and the size (diameter) of an adsorbate such as a gas or ion is important (see, for example, Patent Documents 2 and 3).

  In order to effectively use the inside and outside of the CNT, which is a hollow material, (1) a space is required inside the CNT to sufficiently adsorb an adsorbate such as gas and ions, and at the same time, (2) gas A space that can sufficiently adsorb adsorbed substances such as ions and ions is required outside the CNT.

  Although the diameter of CNT is theoretically 0.4 nm or more, it is known that in practice it is approximately 0.7 nm or more. If the diameter of the adsorbate is very small compared to the CNT diameter, such as hydrogen gas, CNTs with the smallest possible diameter should be arranged as closely as possible to maximize the CNT surface area in the substrate unit area. One of the means. As one of the means, a bundle structure as shown in Patent Document 2 is also effective. Patent Document 2 describes that the number of adsorption sites for a gas having a small diameter such as hydrogen can be increased by bundling CNTs while controlling the diameter of CNTs. For adsorbates having a small diameter, it is possible to use the space between the bundles even in a bundled state. Therefore, bundling CNTs is one effective means.

  However, for example, if the adsorbate is a solvated ion and has a diameter of about 1 to 2 nm, it is difficult to use the inside of the CNT without using a CNT having a sufficiently large diameter with respect to the adsorbate. Become. Moreover, even if the CNTs are bundled, the adsorbate cannot enter the space between the bundles, so that the outside of the CNTs cannot be used effectively. For this reason, bundling CNTs for adsorbents with a large diameter has not been considered an effective means. From the above, it has been considered that it is necessary to control the CNT diameter and the CNT interval to predetermined values without bundling, particularly for the adsorbate having a diameter as large as the CNT diameter.

  FIG. 5 shows the relative relationship between the adsorbate and the adsorbate. When the diameter of the adsorbate is D1, if it is limited to the outside of the CNT, it is considered that the CNT surface area utilization efficiency is increased when the interval between the CNTs is about 2 × D1, as shown in FIG. Here, the interval between the CNTs is defined as the outermost interval between the CNTs as shown in FIG.

  FIG. 6 is a graph showing the relationship between the CNT diameter and the ratio of the CNT surface area / substrate unit area when the CNT interval is kept constant. In deriving the surface area, it was assumed that vertically aligned brush-like CNTs were arranged on the substrate in the three-way closest manner, and the CNT diameter was used as a parameter.

FIG. 6 shows that the ratio of CNT surface area / substrate unit area is maximized when the CNT diameter is the same as the CNT interval. For example, when the CNT interval is about 2 × D1 as described above, it can be said that the surface area is maximized when the CNT diameter is also about 2 × D1. However, the inside of the CNT has a larger curvature than the outside of the CNT, and considering the diameter of the adsorbate, it is considered that the entire surface area cannot be used effectively as it is. For this reason, it has been considered that the CNT diameter is desirably about 3 × D1 or more as shown in FIG.
JP 2004-96173 A JP 2004-142365 A JP 2005-185950 A

  As described above, the surface area can be improved by arranging single CNTs at a CNT diameter and CNT interval suitable for the adsorbate diameter.

  By the way, in the above description, it was assumed that the inside of the CNT was used. However, since the CNT immediately after synthesis is generally closed with a cap structure, in order to use the inside of the CNT, a part of the CNT is opened. There is a need. As the opening method, a known method such as a heat treatment method or a method using an acid can be used, but in any case, an extra step has to be performed after the synthesis of CNTs. For this reason, the subject which raises a cost existed.

  In addition, the opening process of CNTs varies greatly depending on the quality of the synthesized CNTs and the like, and there is a problem that opening conditions have to be determined for each CNT synthesis condition. As far as opening processing by heat treatment is concerned, since the opening of CNTs starts rapidly at a temperature above a certain threshold, if a load above a certain temperature is applied, the CNTs will often not burn. It was.

  Furthermore, it is said that the shape of a single CNT, particularly a single-walled CNT, is often deformed when immersed in an electrolytic solution after synthesis. In this case, as shown in FIG. 8 (b), when the CNT is deformed so that a part thereof is smaller than the diameter of the adsorbate, the adsorbate can be introduced into the CNT even if it is opened. There are problems that the surface area cannot be increased because of difficulty, and that stress is applied when the shape is deformed, and the CNT is detached from the substrate.

  For these reasons, there has been a need for a structure that can improve the surface area without performing an opening process, that is, without using the inner surface of the CNT, and a structure that is stable against external influences.

  Accordingly, an object of the present invention is to provide a carbon nanotube bundle and a carbon nanotube structure which can increase the surface area without performing an opening treatment and are structurally stable.

The present invention has been made to solve the above-described conventional problems, and is a carbon nanotube bundle formed by bundling a plurality of carbon nanotubes, and satisfies the following relational expressions (1) and (2): The carbon nanotube bundle is characterized in that the structure of the bundle and the number of carbon nanotubes forming the bundle are configured so that A exists.
S1 <S2 (1)
L1> 2 × L2 (2)
In the formula, S1 represents the area of the cut surface when the bundle is cut in a plane perpendicular to the axial direction of the bundle, L1 represents the outer peripheral length of the cut surface, and S2 is The area of the circle A is represented, and L2 represents the circumferential length of the circle A.

  Here, the circle A represents a cross section of an isolated CNT to be compared. That is, the significance of the equations (1) and (2) is that the cross-sectional area S1 of the CNT bundle of the present invention is smaller than the cross-sectional area S2 of the isolated CNT to be compared, but the cross-sectional area of the isolated CNT is The outer peripheral length L1 (that is, the outer surface area of the CNT bundle) of the cross section of the CNT bundle of the present invention is larger than twice the circumferential length L2 (that is, the sum of the inner surface area and outer surface area of the isolated CNT). is there.

  In the case where there is a circle A that satisfies such a condition, by using the CNT bundle of the present invention instead of the isolated CNT having a cross section corresponding to the circle A and subjected to opening treatment, An increase in CNT surface area can be achieved without subjecting the bundle to an opening treatment. However, it is assumed that the lengths of the CNT bundle of the present invention and the isolated CNT are the same.

  More specifically, by satisfying S1 <S2 in equation (1), the number of bundles contained per unit volume (the number of CNTs for the isolated CNT to be compared) can be increased. CNT surface area can be improved. Furthermore, by satisfying L1> 2 × L2 in the formula (2), the outer surface area of one CNT bundle that has not been subjected to opening treatment is the inner surface area and outer surface area of one isolated CNT subjected to opening treatment as a comparison target. Therefore, it is possible to provide a CNT having a large surface area without performing an opening process.

  In addition, by forming a bundle, it is possible to provide a structurally stable CNT that is less susceptible to external influences than an isolated CNT.

  Note that the advantages of the present invention can be obtained even if L1> 2 × L2 is not completely satisfied, considering the merit of being structurally stable without performing the opening process. If at least L1> L2 is satisfied, an area larger than the outer surface area of the conventional isolated CNT can be obtained. In this case, the effect that the outer surface area of the CNT bundle becomes larger than the sum of the inner surface area and the outer surface area of the isolated CNT cannot be obtained, but an effect that is structurally stable can be obtained.

  Further, it is not necessary for the entire CNT bundle to satisfy the above condition, and it is possible to realize an improvement in surface area if a bundle satisfying the above condition is included in a part of the CNT bundle.

  Examples of the structure of the CNT bundle include a three-way close-packed structure and a square close-packed structure, but are not limited thereto. Since the effect of improving the surface area is particularly remarkable, a three-way close-packed structure is most preferable. Here, the three-way close-packed structure means a structure in which the centers of three adjacent circles form an equilateral triangle as shown in FIG. 1A, and the square close-packed structure means four adjacent ones as shown in FIG. A structure in which the center of a circle forms a square.

  Moreover, it is not necessary to bundle CNTs having the same diameter, and there is no problem even if CNTs having different diameters are bundled. Further, the number of CNT layers is not limited, but single-walled CNTs may be used.

  The number of CNTs forming the bundle can be easily calculated according to the structure of the CNT bundle. As will be described later, there are 13 or more in the three-way close-packed structure and 14 or more in the square close-packed structure.

In the present invention, it is preferable that the circle A further satisfies the following relational expression (3).
Y1 ≦ 0.25Y2 (3)
In the formula, Y1 represents the average diameter of the carbon nanotubes forming the bundle, and Y2 represents the diameter of the circle A.

  Thus, when the average diameter of the individual CNTs forming the bundle is considerably lower than the diameter of the circle A (the diameter of the isolated CNT to be compared), the effect of the present invention of increasing the surface area is more efficient. Can be achieved.

  In addition, numerical value 0.25 in said Formula (3) is a value calculated theoretically regarding a three-way close-packed structure and a square close-packed structure. This point will be described later.

  Since the diameter of the CNT is approximately 0.7 nm or more and 100 nm or less, 0.7 ≦ Y1 ≦ 100 × 0.25 and 2.8 ≦ Y2 ≦ 100 in the range satisfying the formula (3). .

  A specific embodiment of the present invention is a carbon nanotube bundle formed by bundling a plurality of carbon nanotubes, wherein the bundle has a three-way close-packed structure, and the number of carbon nanotubes forming the bundle is 13 The carbon nanotube bundle characterized by being more than this is mentioned.

  With this configuration, the above-described effects of the present invention can be efficiently achieved in a stable bundle structure called a three-way close-packed structure. The upper limit of the number of carbon nanotubes is not particularly limited, but is considered to be about 100 or less.

  Another specific aspect of the present invention is a carbon nanotube bundle formed by bundling a plurality of carbon nanotubes, wherein the bundle has a square close-packed structure and the number of carbon nanotubes forming the bundle Is a carbon nanotube bundle characterized by having 14 or more.

  With this configuration, the above-described effects of the present invention can be efficiently achieved in a stable bundle structure called a square close-packed structure. The upper limit of the number of carbon nanotubes is not particularly limited, but is considered to be about 100 or less.

  In the present invention, the carbon nanotube is preferably a metallic carbon nanotube.

  As a result, electron conductivity can be increased, and CNTs can be used for electrodes and the like. Note that not all CNTs need to be metallic. In general, CNTs are known to exhibit both semiconducting and metallic properties due to differences in chirality, and the ratio of semiconducting and metallic properties is known to be 2: 1 stochastically. By comprising metallic CNTs with this ratio (1/3) or more, the above effect can be obtained more than in the normal case.

  In the present invention, it is preferable that at least a part of the plurality of carbon nanotubes are electrically connected to each other.

  This makes it possible to maintain electronic conduction through other CNTs even when the CNT conductivity is partially lost, such as when some CNTs are peeled off from the substrate. Can be used effectively.

  Further, the present invention is a structure comprising a substrate and the carbon nanotube bundle, wherein the bundle has an axial direction oriented in a direction perpendicular to the substrate, and the bundle includes: A plurality of structures are arranged on the substrate at predetermined intervals.

  When the CNT bundle described above is vertically aligned on the substrate, the CNT surface area per unit area of the substrate can be efficiently improved. Moreover, the surface area of a bundle outer surface can be utilized effectively by arrange | positioning the said bundle at a predetermined space | interval.

  The vertical alignment of the CNT bundle does not mean that the CNT bundle is strictly perpendicular to the substrate. One end of the CNT bundle is fixed directly or indirectly to the substrate, and the other end is the substrate. It only has to be free from. However, it is possible to further improve the surface area when arranged in a state close to vertical.

  Further, the predetermined interval between the CNT bundles may be an interval that allows the adsorbate targeted by the structure to easily approach the bundle, and as described above, about twice the diameter of the adsorbate. Or more than that is preferable. On the other hand, if the predetermined interval is too wide, the CNT surface area per unit unit area of the substrate is reduced. Therefore, an appropriate interval may be determined in consideration of this viewpoint. Specifically, an interval of about 2 to 10 nm can be exemplified.

  A specific embodiment of the invention is illustrated in FIG. The present invention improves the surface area by using the carbon nanotube bundle in place of the isolated carbon nanotubes in a structure in which isolated carbon nanotubes are erected at a predetermined interval as in Patent Document 3, for example. And structural stability.

  In the present invention, it is preferable that each carbon nanotube constituting the bundle is not subjected to opening treatment at the free end thereof. As a result, it is possible to avoid the above-described complexity when examining the conditions during the opening process, the problem of deformation of the CNT shape due to external force, and the problem of CNT peeling off from the substrate. Further, even if no opening treatment is performed, an improved surface area can be achieved due to the properties of the bundle.

  Moreover, in this invention, it is preferable that the said board | substrate has electroconductivity.

  Thereby, the substrate can be used as an electrode as it is, and device application becomes possible. Examples of the conductive material include aluminum, copper, stainless steel, and conductive silicon, but are not limited to these materials.

  In the present invention, it is preferable that the carbon nanotube bundle is electrically connected to the substrate.

  Thus, the CNT bundle and the substrate can be integrated and used for the electrode.

  In the present invention, the substrate preferably has a thickness of 100 μm or less.

  As a result, the substrate can be easily bent and applied to a wound device or the like.

  Furthermore, the substrate preferably has a thickness of 50 μm or less.

  As a result, the substrate can be further easily bent.

  According to the present invention, it is possible to provide a carbon nanotube bundle and a carbon nanotube structure that are increased in surface area and structurally stable without performing an opening treatment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a case where cylindrical CNTs having the same diameter are bundled in a three-way close-packed structure will be described. In the present invention, there is no problem even if CNTs having different diameters are bundled. Even if the three-way close-packed structure is not perfect, there is no problem as long as it is bundled to satisfy the conditions.

  FIG. 1 shows a comparison of the cross section of a CNT bundled in a three-way close-packed structure (FIG. 1 (a)), which is one of the present invention, and the cross section of a conventional isolated CNT (FIG. 1 (b)). . In the present invention, the surface area is increased and the structure is stabilized by using bundled CNTs as shown in FIG. Regarding structural stabilization, a structure resistant to stress and the like can be provided by supporting a plurality of CNTs with each other. Hereinafter, the surface area improvement will be described.

  FIG. 2 is a perspective view of a bundle of carbon nanotubes (FIGS. 2A and 2B) and an isolated carbon nanotube (FIGS. 2C and 2D), and a cross section in a plane perpendicular to the axial direction. The figure is shown. In the present invention, the cross section of one isolated carbon nanotube is replaced with a circle A.

  3A to 3F are views for explaining the diameter Y, the outer peripheral length L, and the area S of the carbon nanotube. The outer peripheral length L is indicated by a thick line in FIG. The area S is indicated by a mesh line.

When the diameter of one CNT bundled into a three-way close-packed structure, which is one of the present invention, is Y1, and the number of bundles is k, L1 and S1 can be expressed by the following equations.
L1 = (1 + k / 2) πY1
^{S1 = πkY1 2/4 + (} √3-π / 2) (k-2) Y1 2/4
Next, when the diameter of the cross section (that is, the circle A) of one isolated CNT to be compared is Y2, L2 and S2 can be expressed by the following equations.
L2 = πY2
S2 = πY2 ^2/4
Here, it is shown that there may exist a circle A that satisfies the relational expressions (1) and (2) related to the present invention. For simplicity, it is assumed that the lengths of the CNTs are all the same.

  FIG. 4 shows the relationship between the number of bundles k and Y1 / Y2 when the relational expressions (1) and (2) are satisfied (illustrated as k ≦ 40). In FIG. 4, the line indicated by ▲ represents S1 = S2, and the region below this line satisfies the relational expression (1): S1 <S2. The line indicated by x represents L1 = 2 × L2, and the relational expression (2): L1> 2 × L2 is satisfied in the region above this line. As mentioned above, the area | region shown with the oblique line is the range which satisfy | fills both the said relational expressions (1) and (2). That is, as shown in FIG. 4, when the number of bundles is set to 13 or more, there exists a circle A that satisfies both the relational expressions (1) and (2). Similarly, from FIG. 4, when the circle A exists, the ratio of Y1 / Y2 is 0.25 or less, but considering that the diameter Y1 of the CNT is approximately 0.7 nm or more, it is the diameter of the circle A. Y2 is 2.8 nm or more.

  In the following Tables 1 to 3, the Y1 range, the surface area ratio range, and the establishment / absence of the condition when the value of Y2 is assumed to be 2 nm, 3 nm, or 4 nm are described. In derivation of Tables 1 to 3, the condition of Y1> 0.7 nm was added since the diameter of CNT was approximately 0.7 nm or more. In the table, the description of the surface area ratio is the outer surface area of the bundled CNTs / the total of the inner surface area and the outer surface area of one isolated CNT to be compared.

表１より、比較用単一カーボンナノチューブの直径（円Ａの直径Ｙ２）が２ｎｍの場合は、すべてのバンドル数において条件を満たさないことがわかる。

From Table 1, it can be seen that when the diameter of the single carbon nanotube for comparison (diameter Y2 of the circle A) is 2 nm, the condition is not satisfied in all the bundle numbers.

  From Table 2, it can be seen that when the diameter of the comparative single carbon nanotube is 3 nm, the condition is satisfied in the range of the bundle number k = 13 to k = 17. In the case of Y1 = 0.7 nm, it can be confirmed that the surface area ratio is improved by 13% at the bundle number k = 17.

  From Table 3, it can be seen that when the diameter of the comparative single carbon nanotube is 4 nm, the condition is satisfied in the range of the bundle number k = 13 to k = 31. In the case of Y1 = 0.7 nm, it can be confirmed that the surface area ratio is improved by 45% at the bundle number k = 31.

  Next, a case where cylindrical CNTs having the same diameter are bundled in a square close-packed structure will be described. In the present invention, there is no problem even if CNTs having different diameters are bundled. Moreover, even if it is not a square close-packed structure, there is no problem as long as it is bundled so as to satisfy the conditions.

  FIG. 11 shows a cross-sectional view of CNTs bundled in a square close-packed structure in the present invention.

When the diameter of one CNT bundled in a square close-packed structure is Y1 and the number of bundles is k, L1 and S1 can be expressed by the following equations.
L1 = (1 + k / 2) πY1
^{S1 = πkY1 2/4 + (} 4-π) (k-2) Y1 2/8
When the diameter of the cross section (that is, the circle A) of one isolated CNT to be compared is Y2, L2 and S2 can be expressed by the above-described equations.

  Next, it is shown that there can exist a circle A that satisfies the relational expressions (1) and (2) related to the present invention. For simplicity, it is assumed that the lengths of the CNTs are all the same.

  FIG. 12 shows the relationship between the number of bundles k and Y1 / Y2 when the relational expressions (1) and (2) are satisfied (illustrated as k ≦ 40). In FIG. 12, the line indicated by ▲ represents S1 = S2, the line indicated by × represents L1 = 2 × L2, and the area indicated by the oblique lines satisfies both the relational expressions (1) and (2). It is. That is, from FIG. 12, when the number of bundles is set to 14 or more, there exists a circle A that satisfies both the relational expressions (1) and (2). Similarly, from FIG. 12, when the circle A exists, the ratio of Y1 / Y2 is 0.25 or less, but considering that the diameter of the CNT is approximately 0.7 nm or more, Y2 which is the diameter of the circle A Becomes 2.8 nm or more.

  In the following Tables 4 to 6, the Y1 range, the surface area ratio range, and the establishment / absence of the condition when the value of Y2 is assumed to be 2 nm, 3 nm, or 4 nm are described. As above, the condition of Y1> 0.7 nm was added. In the table, the description of the surface area ratio is the outer surface area of the bundled CNTs / the total of the inner surface area and the outer surface area of one isolated CNT to be compared.

表４より、比較用単一カーボンナノチューブの直径（円Ａの直径Ｙ２）が２ｎｍの場合は、すべてのバンドル数において条件を満たさないことがわかる。

From Table 4, it can be seen that when the diameter of the single carbon nanotube for comparison (diameter Y2 of the circle A) is 2 nm, the condition is not satisfied in all the bundle numbers.

  From Table 5, it can be seen that when Y2 is 3 nm, the condition is satisfied in the range of the bundle number k = 14 to k = 16. In the case of Y1 = 0.7 nm, it can be confirmed that the surface area ratio is improved by 6% at the bundle number k = 16.

  From Table 6, it can be seen that when Y2 is 4 nm, the condition is satisfied in the range of the bundle number k = 14 to k = 28. In the case of Y1 = 0.7 nm, it can be confirmed that the surface area ratio is improved by 34% at the bundle number k = 28.

  As described above, the present invention improves the surface area particularly in the case where the diameter of the adsorbate is large, that is, in the region where the diameter of the CNT cross section has been increased in order to effectively use the surface area inside the CNT (2.8 nm or more). It was found that the effect of was achieved. As shown in FIG. 7, considering that CNTs having a diameter approximately three times that of the adsorbate were synthesized in the past, a large effect was obtained in the region where the adsorbate diameter was 1 nm or more. It can be said that can be obtained. In addition, as described above, the present invention has an effect that the process is stable because the opening process is not performed. Furthermore, since a plurality of CNTs are bundled, the structure is stable. It has the effect.

In addition, the diameter of CNT, the outer peripheral length of a CNT bundle, and an area can be evaluated using means, such as TEM. For example, the diameter, outer peripheral length, and area can be derived from a TEM photograph to confirm the effect of the present invention.
(Embodiment)
In this embodiment, a basic form of the carbon nanotube structure of the present invention is shown. Hereinafter, detailed embodiments will be described along the manufacturing process. FIG. 9 shows a flowchart of the present embodiment.

Reference numeral 901 denotes a substrate preparation process. Any material may be used for the substrate, but a conductive material is preferable. The thickness of the substrate is preferably 100 μm or less, more preferably 50 μm or less. As a typical substrate, Si, SiO ₂ , quartz, aluminum, copper, SUS, or the like can be used, but is not limited thereto. In the substrate preparation process, the substrate is cleaved, cleaned, and the like. Although cleavage and cleaning of the substrate are optional, it is preferable to perform cleaning. As substrate cleaning, organic cleaning, acid cleaning, or the like can be performed according to the situation.

  In order to synthesize CNT, it is necessary to dispose a catalyst on the substrate. In the present invention, the catalyst forming means is not limited. A substrate on which a catalyst has been formed in advance may be prepared in the substrate preparation step, or the catalyst may be formed after substrate preparation as in 902. Moreover, you may use the board | substrate containing a catalyst component like SUS.

  Typical catalyst materials can include any of Fe, Ni, Co, Cu, Mo, Mn, Zn, Pd, Pt, V, and composites thereof. However, it is not limited to these. As a method for forming the catalyst, a vacuum sputtering method, a chemical vapor deposition method, a physical vapor deposition method, a screen printing method, an electroplating method, a sol-gel method, an arc plasma gun, or the like can be used, but is not limited thereto.

  In order to form a CNT bundle, it is preferable to pattern the catalyst in accordance with the target bundle structure before synthesizing the CNT. As a patterning method, various methods such as a photolithography method and electron beam drawing are possible, and any method may be used as long as the purpose is achieved. In addition, since it is also possible to bundle it after CNT synthesis | combination, patterning of a catalyst is not necessarily essential.

  It is also possible to use a catalyst support material as the substrate. In this case, there is an advantage that the distribution of the CNT diameter can be easily aligned. Representative catalyst support materials include, but are not limited to, anodic oxide films, zeolites, mesoporous silica, magnesium oxide, aluminum oxide, and the like.

  Reference numeral 903 denotes a carbon nanotube synthesis step. In this step, CNTs are synthesized on the substrate. As the synthesis method, an arc discharge method, a laser ablation method, a thermal CVD method, a plasma CVD method, or the like can be used. However, when the CNT is directly synthesized on the substrate, the CVD method is preferably used. As the carbon source, hydrocarbon gases such as methane, ethylene and acetylene, alcohols such as methanol and ethanol, carbon monoxide and the like can be used. In the synthesis, it is general to use an inert gas such as argon as a carrier gas without using only a carbon source.

  If CNTs are synthesized on a substrate on which a catalyst has been patterned in advance, bundled CNTs can be easily formed.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
Example 1
An aluminum foil having a substrate thickness of 30 μm is used for the substrate. After the substrate is ultrasonically cleaned with acetone for 5 minutes, the catalyst metal Fe is patterned and formed. The patterning of the catalyst is performed using electron beam drawing. In the patterning, 30 circular catalysts having a diameter of 0.7 nm are arranged in a three-way close-packed structure in a state of circumscribing each other, and this is set as one unit, and the interval between adjacent units is set to 3 nm, and the apex of the three-way close-packed structure and Place in the center. Thereafter, carbon nanotubes are synthesized. The synthesis is performed using a thermal CVD method, ethylene gas is used as the carbon source, and argon gas is used as the carrier gas. The synthesis pressure is atmospheric pressure and the synthesis is performed for 30 minutes. The synthesis temperature is 650 ° C.
(Example 2)
As in Example 1, an aluminum foil having a thickness of 30 μm was used for the substrate, and the substrate was ultrasonically cleaned with acetone for 5 minutes, and then Fe as a catalyst metal was patterned. The patterning of the catalyst is performed using electron beam drawing. In the patterning, 15 circular catalysts having a diameter of 1 nm are arranged in a three-way close-packed structure in a state of circumscribing each other, and this is set as one unit, and the interval between adjacent units is set to 3 nm at the apex and center of the three-way close-packed structure. Arrange. Thereafter, carbon nanotubes are synthesized. The synthesis is performed using a thermal CVD method, ethylene gas is used as the carbon source, and argon gas is used as the carrier gas. The synthesis pressure is atmospheric pressure and the synthesis is performed for 30 minutes. The synthesis temperature is 650 ° C.
(Comparative Example 1)
As in Example 1, an aluminum foil having a substrate thickness of 30 μm is used for the substrate. After the substrate is ultrasonically cleaned with acetone for 5 minutes, the catalyst metal Fe is patterned and formed. The patterning of the catalyst is performed using electron beam drawing. In the patterning, a circular catalyst having a diameter of 4 nm is arranged at the apex and center of the three-way close-packed structure with an interval of 3 nm. Thereafter, carbon nanotubes are synthesized. The synthesis is performed using a thermal CVD method, ethylene gas is used as the carbon source, and argon gas is used as the carrier gas. The synthesis pressure is atmospheric pressure and the synthesis is performed for 30 minutes. The synthesis temperature is 650 ° C.

After the synthesis, heat treatment is performed at 550 ° C. for 30 minutes in an oxygen atmosphere in order to perform opening treatment.
(Comparative Example 2)
As in Example 1, an aluminum foil having a substrate thickness of 30 μm is used for the substrate. After the substrate is ultrasonically cleaned with acetone for 5 minutes, the catalyst metal Fe is patterned and formed. The patterning of the catalyst is performed using electron beam drawing. In the patterning, a circular catalyst having a diameter of 4 nm is arranged at the apex and center of the three-way close-packed structure with an interval of 3 nm. Thereafter, carbon nanotubes are synthesized. The synthesis is performed using a thermal CVD method, ethylene gas is used as the carbon source, and argon gas is used as the carrier gas. The synthesis pressure is atmospheric pressure and the synthesis is performed for 30 minutes. The synthesis temperature is 650 ° C.

After the synthesis, heat treatment is performed at 600 ° C. for 30 minutes in an oxygen atmosphere in order to perform opening treatment.
(result)
When a part of the carbon nanotubes formed in Example 1 are extracted together with the substrate and evaluated by TEM, 30 CNTs having a diameter of 0.7 nm are bundled in a three-way close-packed structure, and the bundles are arranged at intervals of 3 nm. I can confirm that.

  When a part of the carbon nanotubes formed in Example 2 are extracted and evaluated by TEM, it is confirmed that 15 CNTs having a diameter of 1 nm are bundled in a three-way close-packed structure, and the bundles are arranged at intervals of 3 nm. be able to.

  When a part of the carbon nanotubes formed in Comparative Example 1 is extracted and evaluated by TEM, it can be confirmed that CNTs having a diameter of 4 nm are arranged at intervals of 3 nm.

  In Comparative Example 2, it is considered that most of the carbon nanotubes burn and disappear because the opening heat treatment temperature is too high.

  When the BET evaluation of the carbon nanotubes produced in Examples 1 and 2 and Comparative Example 1 was performed, the surface area was improved by about 40% in Example 1 and by about 7% in Example 2 compared to Comparative Example 1. Is confirmed.

  Further, when an electric double layer capacitor is produced using the carbon nanotube structures produced in Examples 1 and 2 and Comparative Example 1 as electrodes, it is expected that in Comparative Example 1, the carbon nanotubes will be peeled off by about half after the electrolyte is impregnated. The When the characteristics are evaluated with respect to the capacitance of the capacitor, it is confirmed that the characteristic improvement is about 3 times in Example 1 and about 2 times in Example 2 as compared with Comparative Example 1.

  By using the present invention, the surface area of CNT per unit area can be improved and structurally stable CNTs can be provided. For example, hydrogen storage materials, Li battery electrode materials, electric double layer capacitor materials It can be used for

(A) is the figure which showed the cross section of CNT bundled in the three-way close-packed structure which is one of this invention, (b) is the figure which showed the cross section of the conventional single CNT. (A) is a perspective view of a carbon nanotube bundle which is one of the present invention, (b) is a sectional view thereof, (c) is a perspective view of an isolated carbon nanotube, and (d) is a sectional view thereof. is there. It is a figure explaining the diameter Y, the outer periphery length L, and the area S in this invention and the conventional carbon nanotube, (a), (c) and (e) are explanatory drawings of the carbon nanotube bundle of this invention, (b) ), (D), and (f) are explanatory views of a conventional single carbon nanotube. It is a graph which shows the relationship between bundle number k and Y1 / Y2 in the case of satisfy | filling relational expressions (1) and (2) in the bundle of the three-way close-packed structure which is one of this invention. In description of a prior art example, (a)-(d) is a figure which shows the relative relationship of an adsorbate and a to-be-adsorbed object. In description of a prior art example, it is a graph showing the relationship between CNT diameter and the ratio of CNT surface area / substrate unit area when the CNT interval is kept constant. (A) (b) is a figure which shows the relationship between the CNT diameter in a CNT, and an adsorbate diameter in description of a prior art example. (A) (b) is a figure which shows the relationship between CNT and adsorbate when a shape changes in description of a prior art example. It is a flowchart which shows the process which manufactures the structure in this invention. It is a figure which shows the carbon nanotube bundle formed in the predetermined space | interval on the board | substrate in this invention. It is the figure which showed the cross section of CNT bundled in the square close-packed structure which is one of this invention. It is a graph which shows the relationship between the bundle number k and Y1 / Y2 in the case of satisfy | filling relational expressions (1) and (2) in the square close-packed structure bundle which is one of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Bundled carbon nanotube 102 Isolated single carbon nanotube 501 Carbon nanotube 502 Adsorbed material 801 Deformed carbon nanotube 901 Substrate preparation step 902 Catalyst formation step 903 Carbon nanotube synthesis step 1001 Substrate 1002 Bundled carbon nanotube

Claims (11)

A carbon nanotube bundle formed by bundling a plurality of carbon nanotubes,
A carbon nanotube bundle characterized in that the structure of the bundle and the number of carbon nanotubes forming the bundle are configured so that a circle A satisfying the following relational expressions (1) and (2) exists.
S1 <S2 (1)
L1> 2 × L2 (2)
In the formula, S1 represents the area of the cut surface when the bundle is cut in a plane perpendicular to the axial direction of the bundle, L1 represents the outer peripheral length of the cut surface, and S2 is The area of the circle A is represented, and L2 represents the circumferential length of the circle A. The carbon nanotube bundle according to claim 1, wherein the circle A further satisfies the following relational expression (3).
Y1 ≦ 0.25Y2 (3)
In the formula, Y1 represents the average diameter of the carbon nanotubes forming the bundle, and Y2 represents the diameter of the circle A. A carbon nanotube bundle formed by bundling a plurality of carbon nanotubes,
A carbon nanotube bundle, wherein the bundle has a three-way close-packed structure, and the number of carbon nanotubes forming one bundle is 13 or more. A carbon nanotube bundle formed by bundling a plurality of carbon nanotubes,
A carbon nanotube bundle, wherein the bundle has a square close-packed structure and the number of carbon nanotubes forming one bundle is 14 or more.   The carbon nanotube according to claim 1, wherein the carbon nanotube is a metallic carbon nanotube.   The carbon nanotube according to claim 1, wherein at least a part of the plurality of carbon nanotubes are electrically connected to each other. A substrate,
A structure comprising the carbon nanotube bundle according to any one of claims 1 to 6,
The bundle is characterized in that an axial direction of the bundle is oriented in a direction perpendicular to the substrate, and a plurality of the bundles are arranged on the substrate at a predetermined interval.   The structure according to claim 7, wherein the substrate has conductivity.   The structure according to claim 7 or 8, wherein the carbon nanotube bundle is electrically connected to the substrate.   The structure according to claim 7, wherein the substrate has a thickness of 100 μm or less.   The structure according to claim 7, wherein the substrate has a thickness of 50 μm or less.

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