JP5574257B2 - Reusable substrate for producing carbon nanotubes, substrate for producing carbon nanotubes and method for producing the same - Google Patents

Description

  The present invention relates to a carbon nanotube generating reusable base material, a carbon nanotube generating base material, and a method for producing the same, and a carbon nanotube that can contribute to improving the productivity of aligned carbon nanotube aggregates by repeatedly using the base material. It relates to a substrate for generation.

  A carbon nanotube (hereinafter also referred to as “CNT”) is a carbon structure having a structure in which a carbon sheet formed by arranging carbon atoms in a hexagonal shape in a plane is closed in a cylindrical shape. There are multi-layered and single-layered CNTs, all of which are in terms of mechanical strength, optical properties, electrical properties, thermal properties, molecular adsorption functions, etc., from electronic device materials, optical element materials, conductive materials. Development as functional materials such as functional materials is expected. Among CNTs, single-walled CNTs have electrical characteristics (very high current density), thermal characteristics (thermal conductivity comparable to diamond), optical characteristics (light emission in the optical communication band wavelength region), hydrogen storage capacity, and metals. In addition to being excellent in various properties such as catalyst supporting ability, and having both properties of a semiconductor and a metal, it has attracted attention as a material for nanoelectronic devices, nanooptical elements, energy storage bodies, and the like.

  When CNTs are effectively used for these applications, a bundle, film, or agglomerate aggregate in which a plurality of CNTs are aligned in a regular direction is formed. It is desirable to exhibit both functional and optical functionality. CNT is a material having a one-dimensional structure with an extremely high aspect ratio, and its function is highly directional. Therefore, if each CNT constituting the CNT aggregate (structure) is oriented in a regular direction, the direction of the function of each CNT can be aligned, and as a result, a highly functional A CNT aggregate can be obtained.

  In other words, an aligned CNT aggregate in which each CNT is aligned in a regular direction is transmitted in the direction of alignment as compared to a non-oriented CNT aggregate in which the direction of each CNT is irregular. High directivity in characteristics. Due to this high directivity, CNT aggregates have better electrical properties (eg higher conductivity), better mechanical properties (eg higher strength), better thermal properties (eg higher thermal conductivity) Indicates. Furthermore, such a property that is different between the orientation direction of the CNT aggregate and the other direction, that is, anisotropy, is effective, for example, when it is desired to selectively diffuse and discharge heat in a desired direction. It is suitable for applications such as heat conductive materials. Further, it is desirable that the CNT aggregate has a larger size such as height and length. If such an aligned CNT aggregate is created, the application field of CNT is expected to expand dramatically.

  On the other hand, a chemical vapor deposition method (hereinafter also referred to as a CVD method) is known as one of CNT manufacturing methods (see Patent Document 1 and the like). This method is characterized in that the carbon compound is brought into contact with the metal fine particles of the catalyst in a high temperature atmosphere of about 500 ° C. to 1000 ° C., and various modes such as the type and arrangement of the catalyst, the type of carbon compound and the reaction conditions are various. It is possible to produce CNTs in a changed state, and has attracted attention as being suitable for mass production of CNTs. In addition, this CVD method can produce both single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT), and by using a substrate carrying a catalyst, a large number of CNTs oriented perpendicular to the substrate surface. It has the advantage that it can be manufactured.

Japanese Patent Laid-Open No. 2003-171108 (released on June 17, 2003) JP 2006-27948 A (published February 2, 2006) JP 2007-91485 A (published April 12, 2007)

  In order to form an aligned CNT aggregate on a base material, the density and diameter of the catalyst fine particles on the base material are highly controlled, and the catalyst fine particles are uniformly attached over the entire surface on which the CNTs are grown. Need to be. On the other hand, it is necessary to reuse the base material in order to reduce the cost of producing the aligned CNT aggregate. In order to stably produce aligned CNT aggregates of the same quality by repeatedly using the same substrate, the catalyst fine particles on the substrate are always in an optimal and constant state even when the substrate is reused. There must be.

  Patent Document 2 and Patent Document 3 have a description that the base material and the catalyst once used for CNT production can be used repeatedly in the next CNT production method.

  However, this method has a problem that the growth rate of CNTs is remarkably reduced and an aligned CNT aggregate cannot be obtained. There are two possible reasons for this.

  The first reason is that the catalyst after producing CNTs by the CVD method remains in the form of fine particles and remains on the substrate, but is placed in a high temperature environment of about 800 ° C. during the CVD, so the growth of CNTs. It is considered that the state of the catalyst is changing during the process. For example, there is a possibility that a part of the catalyst is in the base layer. Therefore, there is a possibility that the state of the catalyst changes every time the CVD is repeated.

  The second possibility is considered as follows. Once the base material and catalyst used for CNT production are directly put into the CNT manufacturing apparatus and the next CVD is performed, it is not preferable in terms of production efficiency to change the CVD process depending on the state of the catalyst and the base material. CNT production is carried out by the same process as the first time. Therefore, in the case of a process in which a CNT growth step is performed after the catalyst reduction step, the catalyst reduction step is necessarily performed. There are optimum conditions for the catalyst reduction process, and when the substrate is reused and the same catalyst is subjected to the second reduction process, the catalyst may not be in an optimal state. For example, agglomeration of the catalyst fine particles is promoted, and the particle size of the catalyst fine particles is increased, and the quality such as the diameter of the CNT may be changed.

  For these reasons, when the substrate and catalyst once used for CNT production are used as they are for the next CNT production, it is difficult to maintain the catalyst in an optimal state for CNT growth, and the substrate is reused. It is difficult to obtain the same quality of CNT.

  Patent Document 3 describes a method of forming a new catalyst on a substrate after washing and removing the catalyst remaining on the substrate surface with an acid. In order to remove the catalyst on the substrate surface, a very thin catalyst having a thickness of several nanometers must be uniformly removed from the CNT growth surface of the substrate. For this reason, the catalyst is not peeled off and damage to the base material is likely to occur, which causes deterioration of CNT growth. For example, when a metal substrate is used as the substrate and acid cleaning is performed to remove the catalyst, a location where the catalyst cannot be removed occurs on the substrate, or the metal substrate is corroded by acid. Thus, there is a problem that affects the growth of CNTs. Therefore, there is a demand for a simpler and more stable method for reusing a substrate.

The present invention has been made in view of the above circumstances, and can produce low-cost carbon nanotubes that can stably and efficiently produce high-quality carbon nanotubes even when the substrate is repeatedly reused . substrate and a manufacturing method thereof, as well, and to provide a carbon nanotube generation reusable substrates such as for obtaining the carbon nanotube generation substrate.

  As a result of intensive studies, the present inventors have found that the same base material can be reused repeatedly to stably produce an aligned aggregate of carbon nanotubes with a constant quality at a low cost. Specifically, first, carbon nanotubes formed by orientation on the catalyst layer on the substrate are peeled from the catalyst layer. Next, the base material used as the basis for reusing a base material can be manufactured by implementing the initialization process of the catalyst fine particle in a catalyst layer. Further, without removing the layer in which the catalyst fine particles have been initialized (catalyst initialization layer), a base layer is provided on the layer to cover the catalyst initialization layer. Furthermore, the base material for carbon nanotube production | generation can be manufactured by providing a catalyst on it. It is possible to perform CVD using the carbon nanotube production base material and grow an aligned CNT aggregate on the base material again. By repeating this process, it has been found that it is possible to repeatedly produce aligned carbon nanotube aggregates on the same substrate, and the present invention has been completed.

  That is, the carbon nanotube production reuse base material as an exemplary aspect of the present invention is provided on the surface of the base material, the base material, the base layer serving as the base of the catalyst, and the surface of the base layer And it is provided in the surface on the opposite side to the said base material, The catalyst initialization layer provided with at least 1 catalyst fine particle which does not contain a carbon component is provided, It is characterized by the above-mentioned.

  The substrate is preferably made of metal. It is preferable that a carburization preventing layer for preventing a carbon component from penetrating into the base material is further provided between the base material and the base layer. It is more preferable that a carburization preventing layer for preventing a carbon component from penetrating into the base material is provided on the surface of the base material opposite to the side on which the base layer is located.

  According to another exemplary aspect of the present invention, there is provided a method for producing a reused base material for producing carbon nanotubes, a peeling step of peeling carbon nanotubes formed on a catalyst layer on a base material from the catalyst layer, and the catalyst layer. And an initialization step of initializing the catalyst fine particles by removing the carbon component from the catalyst fine particles remaining in the catalyst.

  The carbon nanotube generating base material as an exemplary aspect of the present invention is provided on the surface of the base material, the base material, the first base layer serving as a base for the catalyst, and the surface of the base layer. A catalyst initialization layer provided on a surface opposite to the base material, the catalyst initialization layer including at least one catalyst fine particle not including a carbon component, and the catalyst initialization layer, wherein the first It is characterized by comprising a second underlayer provided on the side opposite to the underlayer and serving as a base for the catalyst, and a catalyst provided on the second underlayer.

  The substrate is preferably made of metal. It is preferable that a carburization preventing layer for preventing a carbon component from penetrating into the base material is further provided between the base material and the base layer. It is more preferable that a carburization preventing layer for preventing a carbon component from penetrating into the base material is provided on the surface of the base material opposite to the side on which the base layer is located.

  According to another exemplary aspect of the present invention, there is provided a method of manufacturing a base material for producing a carbon nanotube, comprising: a separation step of separating carbon nanotubes formed on a catalyst layer on the substrate from the catalyst layer; An initializing step for initializing the catalyst fine particles by removing the carbon component from the catalyst fine particles, and an undercoat layer on the catalyst layer that has been initialized and serving as a catalyst undercoat on the side opposite to the base material And a catalyst forming step of providing a catalyst on the side opposite to the catalyst layer on the base layer.

  According to the present invention, the same base material can be reused repeatedly in the production of carbon nanotubes, and a uniform and the same quality carbon nanotube aligned aggregate can be obtained on the base material regardless of the number of times of reuse. Therefore, it is possible to prevent a decrease in the production amount and quality of the carbon nanotubes, and it is possible to produce carbon nanotubes with high production efficiency at low cost.

It is a figure showing roughly the layer composition of the reuse base material for carbon nanotube production concerning one embodiment of the present invention. It is a figure which shows roughly the layer structure of the base material for carbon nanotube production | generation which concerns on one Embodiment of this invention. FIG. 3 schematically shows a layer configuration after peeling off an aligned CNT aggregate and a layer configuration after a catalyst initialization step in Example 1. FIG. It is a Raman spectrum of the base-material surface after peeling of the aligned CNT aggregate in Example 1, and after the initialization process of a catalyst. In Example 2, it is a figure which shows schematically the laminated constitution of the base material after 30 times reuse of the base material. 10 is a flowchart illustrating a process of reusing a base material in Example 2. It is a figure which shows the deformation | transformation of a board | substrate typically. It is the figure which showed collectively whether the reuse of a base material was possible. It is a figure which shows typically the structure of the carbon nanotube manufacturing apparatus using the base material for carbon nanotube production | generation which concerns on one Embodiment of this invention.

(CNT aligned aggregate)
In a high carbon concentration environment / atmosphere containing a catalyst activator, CNTs can be grown with high efficiency using the raw material gas from the catalyst on the carbon nanotube production substrate according to the present invention. CNTs can be oriented in a specific direction to form an aligned CNT aggregate.

The single-walled aligned CNT aggregate obtained by using the carbon nanotube-generating reuse base material according to the present invention and the carbon nanotube-generating base material according to the present invention has a high specific surface area, and each CNT is There is an advantageous effect of having an excellent characteristic that the conventional CNT aggregate does not have, such as being oriented in a regular direction and having a low bulk density. Monolayer aligned CNT aggregate, for example, the specific surface area as large as 600m ² / g~2600m ² / g. Such a large specific surface area is effective as a catalyst carrier and energy / material storage material, and is suitable for applications such as supercapacitors and actuators. In addition, each CNT constituting the aligned CNT aggregate is oriented in a regular direction. Therefore, the directionality of the function of each CNT can be aligned, and as a result, a highly functional CNT aggregate can be obtained.

(Orientation)
The orientation evaluation method will be described in detail later. For example, the X-ray diffraction intensity, SEM image or atomic force microscope (also referred to as “AMF”) image obtained by the θ-2θ method or the Laue method is subjected to fast Fourier transform. In the aligned single-walled CNT aggregate obtained by the present invention, the orientation coefficient of Hermann calculated using the intensity profile obtained from the image obtained in the present invention is, for example, -0.5 to 1, preferably from 0 It is 1 or less, more preferably 0.25 or more and 1 or less. Single-walled aligned CNT aggregates in such a range of orientation exhibit good electrical properties, good mechanical properties, good thermal properties, a large specific surface area, high unity, easy handling, and shape processing The property is also good. Moreover, it exhibits sufficient thermodynamic, electrical, and mechanical anisotropy and is suitable for various applications.

  On the other hand, single-walled aligned CNT aggregates whose Hermann orientation coefficient is less than 0 do not exhibit orientation. When the Herman orientation coefficient is less than 0.25, the CNT inclination is 45 °, and the orientation effect is reduced. A single-walled aligned CNT aggregate having a Herman orientation coefficient of 1 is completely aligned.

  In order for the aligned single-walled CNT aggregate to exhibit orientation and a high specific surface area, the height (length) of the aligned single-walled CNT aggregate is preferably in the range of 10 μm to 10 cm. A single-walled aligned CNT aggregate in this height range has good orientation and a large specific surface area. The orientation is improved by setting the height to 10 μm or more. Further, if the height is 10 cm or less, the production can be performed in a short time, so that adhesion of carbon impurities can be suppressed and the specific surface area can be improved. Furthermore, the single-walled aligned CNT aggregate having this height range has high integrity, is easy to handle, and has good shape workability.

The orientation of the aligned CNT aggregate can be evaluated by, for example, at least one of the following methods 1 to 3. That is,
1. When X-ray diffraction intensity is measured by incident X-rays from a first direction parallel to the longitudinal direction of the CNT and a second direction orthogonal to the first direction (θ-2θ method), There exists a θ angle and a reflection direction in which the reflection intensity is greater than the reflection intensity from the first direction, and a θ angle and a reflection direction in which the reflection intensity from the first direction is greater than the reflection intensity from the second direction. Exist.

  2. A diffraction peak pattern showing the presence of anisotropy appears when X-ray diffraction intensity is measured (Laue method) using a two-dimensional diffraction pattern image obtained by X-ray incidence from a direction perpendicular to the longitudinal direction of CNT. To do.

  3. The Herman orientation coefficient is greater than 0 and less than 1 using the X-ray diffraction intensity obtained by the θ-2θ method or the Laue method. More preferably, it is 0.25 or more and 1 or less.

  In the above-mentioned X-ray diffraction method, (CP) diffraction peak due to packing between single-walled CNTs, (002) peak diffraction intensity, and carbon six-membered ring structure constituting single-walled CNTs (100) , (110) The intensity of diffraction peaks in the incident directions of the parallel and perpendicular peaks is also different from each other.

[Configuration of reused carbon nanotube production base and carbon nanotube production base]
The carbon nanotube-generating reuse base material according to the present embodiment is provided on the base material, the surface of the base material, the base layer serving as the base of the catalyst, the surface of the base layer, and the base A catalyst initialization layer provided on a surface opposite to the material and provided with at least one catalyst fine particle not containing a carbon component. In the present specification, the “carbon nanotube generating reusable base material” refers to a carbon nanotube generating base material that has been once used for manufacturing CNT, and can be used again for manufacturing CNT. For example, the base material for producing carbon nanotubes according to the present invention is provided by further providing a base layer on the reuse base material for producing carbon nanotubes and providing a catalyst thereon. Can be obtained.

  In addition, the carbon nanotube generating base material according to the present embodiment is provided on the surface of the base material, the base material, the first base layer serving as a base for the catalyst, and the surface of the base layer. A catalyst initialization layer that is provided on a surface opposite to the substrate and includes catalyst fine particles not containing a carbon component; and on the catalyst initialization layer, the first underlayer; Comprises a second underlayer provided on the opposite side and serving as a catalyst underlayer, and a catalyst provided on the second underlayer.

(Base material)
The carbon nanotube generation reusable base material and the base material provided for the carbon nanotube generation base material may be any member that can carry a carbon nanotube catalyst on its surface, and can maintain its shape even at a high temperature of 400 ° C. or higher. Is preferred. For example, those with a proven track record in CNT production can be used as appropriate. Materials include iron, nickel, chromium, molybdenum, tungsten, titanium, aluminum, manganese, cobalt, copper, silver, gold, platinum, niobium, tantalum, lead, zinc, gallium, indium, gallium, germanium, arsenic, indium, Examples include metals such as phosphorus and antimony, and alloys and oxides containing these metals, or non-metals such as silicon, quartz, glass, mica, graphite, and diamond, and ceramics. Metals are preferable because they are low in cost compared to silicon and ceramics, and in particular, Fe-Cr (iron-chromium) alloys, Fe-Ni (iron-nickel) alloys, Fe-Cr-Ni (iron-chromium-nickel). ) Alloys are preferred.

  The substrate may be in the form of a thin film, a block, or a powder, for example, in addition to the flat plate, and is particularly advantageous when a large amount of the surface area can be obtained for the volume. The main surface of the substrate is a surface having a large area and advantageous for the growth of carbon nanotubes, and means a surface on which carbon nanotubes are actually grown.

  When using a flat base material, there is no restriction | limiting in particular in the thickness of a base material, For example, the thing from about several micrometers thin film to about several cm can be used. Preferably, it is 0.05 mm or more and 3 mm or less. If the thickness of the base material is 3 mm or less, the base material can be sufficiently heated in the CVD process, and the growth failure of the carbon nanotubes can be suppressed, and the cost of the base material can be reduced. If the thickness of the base material is 0.05 mm or more, the deformation of the base material due to carburization is suppressed, and the base material itself is less likely to bend, which is advantageous for transport and reuse of the base material. In addition, the carburization said in this specification means that a carbon component osmose | permeates a base material.

  Although there is no restriction | limiting in particular in the shape and magnitude | size of a flat base material, As a shape, a rectangular or square thing can be used. There is no particular limitation on the size of one side of the substrate, but it is preferably as large as possible from the viewpoint of mass productivity of carbon nanotubes.

(Recycle base material for carbon nanotube production)
The carbon nanotube generation reuse base material in the present embodiment is a carbon nanotube generation base material by performing a layering process of a base film and a catalyst, which will be described later, and then reusing the base material by performing CVD. Carbon nanotube production is possible.

  The reusable base material for producing carbon nanotubes is provided on the base material, the surface of the base material, the base layer serving as the base of the catalyst, and the surface of the base layer, on the opposite side of the base material And a catalyst initialization layer including catalyst fine particles which are provided on the surface and do not include a carbon component.

  A separation step of separating the carbon nanotubes formed on the catalyst layer on the substrate from the catalyst layer (that is, the catalyst layer is a layer containing catalyst fine particles since it has been once used for the production of CNT) ), By removing the carbon component from the catalyst fine particles remaining in the catalyst layer, and by performing an initialization step for initializing the catalyst fine particles, it is possible to produce a reuse base material for producing carbon nanotubes.

A base layer forming step of providing a base layer that is a base of the catalyst on the side of the catalyst initialization layer that has been initialized with respect to the reuse base material for carbon nanotube generation;
By performing a catalyst forming step of providing a catalyst on the underlayer and on the opposite side of the catalyst initialization layer, a carbon nanotube generating substrate described later can be manufactured. Thereby, even if it is the base material once used for manufacture of a carbon nanotube, it can be used for manufacture of a carbon nanotube again.

(Substrate for carbon nanotube production)
The base material for producing carbon nanotubes in the present invention is manufactured by reusing a base material on which CNT has been grown. Since the substrate can be reused, carbon nanotubes of the same quality can be produced repeatedly and stably at a low cost.

  The base material for generating carbon nanotubes is provided on the surface of the base material, the base material, the first base layer serving as a base for the catalyst, and the surface of the base layer, wherein the base material is Provided on the opposite surface, a catalyst initialization layer containing catalyst fine particles not containing a carbon component, and on the catalyst initialization layer, provided on the opposite side of the first underlayer, A second base layer serving as a base of the catalyst; and a catalyst provided on the second base layer.

  An exfoliation step for exfoliating carbon nanotubes formed on the catalyst layer on the substrate from the catalyst layer, and an initialization step for initializing the catalyst fine particles by removing carbon components from the catalyst fine particles remaining in the catalyst layer (That is, the catalyst layer at this time is a layer containing catalyst fine particles since it has been once used for the production of CNT), on the initialized catalyst layer, on the side opposite to the base material By performing a base layer forming step of providing a base layer to be a base of a catalyst and a catalyst forming step of providing a catalyst on the side opposite to the catalyst layer on the base layer, a carbon nanotube generating substrate is obtained. Can be manufactured.

  When manufacturing a substrate for generating carbon nanotubes, a base film is laminated so as to cover a catalyst initialization layer in which catalyst fine particles are initialized, and a catalyst is newly laminated on the base film. A new catalyst is formed on the outermost surface. Therefore, an optimal catalyst can be prepared when the next CVD is performed using the carbon nanotube generating base material. Furthermore, the base film provided between the catalyst and the catalyst initialization layer makes it possible to separate the catalyst once used in the CVD and the catalyst used in the next CVD when the substrate is reused. Therefore, in the step of laminating the base film and the catalyst, it is preferable to form the base film and the catalyst in the order of layers.

  A person skilled in the art thinks that a catalyst once used for CVD is covered with a base film in the reuse of a substrate to form a new catalyst thereon, so that it is not necessary to carry out a catalyst initialization step. Let's go. However, the present inventors have found that when the base film and the catalyst are laminated without performing the catalyst initialization step and the base material is reused, the aligned CNT aggregate may not be generated. From this, it has been found that the catalyst initialization step has a role of improving the growth stability of the aligned CNT aggregate or a role of promoting the growth of the aligned CNT aggregate in the reuse of the base material. It came to.

(Carburization prevention layer)
A carburization preventing layer may be formed on at least one of the front surface and the back surface of the substrate. Of course, it is desirable that a carburizing prevention layer is formed on both the front and back surfaces. This carburizing prevention layer is a protective layer for preventing the base material from being carburized and deformed in the carbon nanotube production process.

  When a metal is used as the material of the base material, there is a possibility that a problem of deformation (warping or the like) of the base material may occur. When the cause of the deformation of the metal base material was examined, the base material was carburized by exposing the base material to a high-temperature carbon atmosphere during the growth of the carbon nanotubes. The inventors have found that deformation occurs. In particular, in a high carbon concentration environment where the ratio of the raw material gas to the total flow rate is about 2 to 20%, the growth rate of the aligned CNT aggregate is improved, but there is a problem that the deformation of the metal base material is increased. The present inventors have found out. In addition, in order to industrially mass-produce carbon nanotubes, it is necessary to increase the substrate area, but the deformation of the substrate may increase as the substrate area increases. In order to reduce the cost of CNT production, it is necessary to reuse the base material for CNT production, but there is a possibility that the deformation of the base material increases every time the reuse is repeated.

  If the base material deforms during CVD, the gas flow near the base material surface changes, and the growth of the carbon nanotubes becomes uneven on the substrate, or the carbon nanotubes are peeled off from the base material. There is a possibility of malfunction. If the deformation of the base material is increased by repeating the reuse of the base material, the growth of the carbon nanotubes itself may be hindered, and a malfunction may occur in the catalyst initialization process and the catalyst formation process. Therefore, deformation of the base material must be prevented when the base material is used repeatedly.

  Therefore, the present inventors have come up with the idea of preventing such problems by providing a carburization prevention layer.

  The carburizing prevention layer is preferably made of a metal or a ceramic material, and particularly preferably a ceramic material having a high carburizing prevention effect. Examples of the metal include copper and aluminum. Examples of the ceramic material include aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, titanium oxide, silica alumina, chromium oxide, boron oxide, calcium oxide, zinc oxide and other oxides, and nitrides such as aluminum nitride and silicon nitride. Among them, aluminum oxide and silicon oxide are preferable because they have a high effect of preventing carburization.

  On the carburizing prevention layer, a catalyst and a base layer for CNT growth described later are formed. When the material of the carburizing prevention layer and the material of the catalyst or the base layer are common, the carburization prevention layer is used as the catalyst or the base layer. It may also serve as a function.

  The thickness of the carburizing prevention layer is desirably 0.01 μm or more and 1.0 μm or less. When the layer thickness is 0.01 μm or more, a carburization preventing effect can be sufficiently obtained. When the layer thickness is 1.0 μm or less, the thermal conductivity of the base material can be prevented from changing, and the base material can be sufficiently heated in the CVD process to grow the carbon nanotubes satisfactorily. As a layer formation (coating) method, for example, a physical method such as vapor deposition or sputtering, a method such as CVD, or a coating method can be applied.

(Underlayer, catalyst)
A catalyst for CNT growth is formed on the substrate. As the catalyst, for example, those that have been used in the production of conventional CNTs can be used as appropriate. Specific examples include iron, nickel, cobalt, molybdenum, and chlorides and alloys thereof. can do. Further, they are preferably layered with an underlayer made of a ceramic material such as alumina, titania, titanium nitride, or silicon oxide. For example, an alumina-iron thin film, an alumina-cobalt thin film, an alumina-iron-molybdenum thin film, etc. can be illustrated. The underlayer is a layer that serves as a base for the catalyst. Note that the term “catalyst” in the term “underlying layer that serves as the base for the catalyst” and “catalyst” in the “catalyst initialization layer” are the same catalyst. It becomes “catalyst fine particles” constituting the “initialization layer”. As the underlayer, various materials can be used as long as they become the underlayer of the catalyst. For example, a metal such as aluminum or titanium may be used, but a ceramic material is preferable because CNT growth is good when the substrate is reused. For example, CNT growth is possible even in the form of an aluminum-iron thin film, an aluminum-iron-molybdenum thin film, etc., but when the substrate is reused according to the present invention, the material used as the base film is the ceramic material. As compared with metal, there is no deterioration during CVD, and CNT growth is good even in the second and subsequent CVD. The thickness of the underlayer is preferably 10 nm or more from the viewpoint of stable CNT growth and improved yield, and preferably 30 nm or less from the viewpoint of production efficiency.

  As the amount of catalyst present, for example, a proven amount can be used for the production of CNTs so far. For example, when iron is used, the thickness is preferably 0.1 nm or more and 100 nm or less, and 0.5 nm. The thickness is more preferably 5 nm or less and particularly preferably 0.8 nm or more and 2 nm or less.

  Either the wet process or the dry process may be applied to the formation of the base layer and the catalyst layer on the surface of the substrate, that is, the base layer formation step and the catalyst formation step referred to in the present invention. For example, a sputtering vapor deposition method or a liquid coating / firing method in which metal fine particles are dispersed in an appropriate solvent can be applied. In addition, the catalyst layer can be formed into an arbitrary shape by combining patterning using well-known photolithography, nanoimprinting, or the like. In the production method of the present invention, a single layer, such as a thin film, a column, a prism, and other complicated shapes by adjusting the patterning of a catalyst to be formed on a substrate and the growth time of CNTs The shape of the aligned CNT aggregate can be arbitrarily controlled.

  In particular, the aligned single-walled CNT aggregate is extremely small in thickness (height) compared to its length and width, but the length and width can be controlled arbitrarily by patterning the catalyst. The thickness dimension can be arbitrarily controlled by the growth time of each single-walled CNT constituting the single-walled aligned CNT aggregate.

  If the catalyst is formed on both the front and back surfaces of the substrate, the aligned carbon nanotube aggregate can be grown on both surfaces of the substrate, which is more desirable from the viewpoint of production efficiency. Of course, it is possible to make the catalyst one side according to the production cost, convenience in the production process, and the like.

  In the base material, the carburization preventing layer on the base material surface, and the catalyst, the arithmetic average roughness Ra of the surface is preferably 3 μm or less. This prevents or reduces the adhesion of carbon stains to the substrate surface, makes it difficult to carburize, and enables high-quality carbon nanotubes to be produced with high efficiency. As described in “JIS B 0601-2001”, the arithmetic average roughness Ra is extracted from the roughness curve by the reference length L in the direction of the average line, and the X-axis is orthogonal to the average line direction of the extracted portion. When the surface profile when the Y axis is taken in the direction of the vertical magnification is expressed by y = f (x), it is obtained by the following equation (1).

(Step of peeling CNT aligned aggregate)
Examples of the method for peeling the aligned CNT aggregate from the substrate include physical, chemical or mechanical peeling methods, for example, a method of peeling using an electric field, a magnetic field, centrifugal force, or surface tension, or mechanically directly. The method of peeling from a base material, the method of peeling from a base material using a pressure and a heat | fever, etc. are applicable. As a simple peeling method, there is a method in which the single-walled aligned CNT aggregate is directly pinched with tweezers and peeled off from the substrate, but it is more preferable to peel off from the substrate using a thin blade such as a cutter blade. It is also possible to suck the single-walled aligned CNT aggregate using a vacuum pump and peel it off from the substrate.

(Catalyst initialization layer, catalyst initialization process)
When the aligned CNT aggregate grown on the base material is peeled off, the catalyst remains on the base material in the form of fine particles without being peeled off. On the surface of the catalyst, for example, when CNT is grown by using CVD, carbon impurities that are considered to have been attached by CVD are attached. The carbon impurities are considered to be carbon compounds such as CNT, graphite-like or amorphous nanoparticles, flake-like substances, etc. that remain without being removed in the peeling process of the aligned CNT aggregate.

  Once the carbon nanotubes are formed, the process of peeling the carbon nanotubes from the layer containing the catalyst fine particles and removing the carbon impurities from the catalyst fine particles remaining in the layer is called the catalyst initialization process. The layer subjected to the process is referred to as “catalyst initialization layer” in the present specification. A specific method for the catalyst initialization process may be selected as appropriate, such as a method of wiping with a nonwoven fabric, a method of cleaning with a liquid such as water or alcohol, and burning carbon impurities such as an oxygen plasma reactor or a UV ozone cleaner. A known method such as an ashing method can be used.

  The catalyst initialization layer preferably includes fine catalyst particles that do not contain a carbon component. When the catalyst initialization layer contains a carbon component, there is a possibility that the growth of CNTs deteriorates when the substrate is reused. This carbon component is thought to be derived from carbon impurities adhering to the catalyst. The absence of a carbon component can be evaluated, for example, by measuring the Raman spectrum of the substrate surface. The carbon component can be detected in the vibration mode of graphite around 1593 cm −1 or the vibration mode of an amorphous carbon compound having low crystallinity near 1350 cm −1, and it is preferable that these peaks are not observed.

  When the base material having the catalyst initialization layer on the outermost surface is installed in a CVD apparatus as it is and the second CVD is performed, the growth of CNT may deteriorate. As a possible cause, there is a possibility that the density and diameter of the catalyst fine particles in the catalyst initialization layer are not maintained in the same optimal state as the first CVD.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
In Example 1, a reuse base material for producing carbon nanotubes was produced.

  FIG. 1 shows an example of a reuse base material for producing carbon nanotubes. First, it has the base material 1-1 for carrying | supporting a catalyst. The substrate 1-1 is preferably made of a metal material. A base layer 1-3 is provided on the main surface of the substrate 1-1. On the underlayer 1-3, a catalyst initialization layer 1-4 provided with at least one carbon component-free catalyst fine particle is provided.

  It is preferable to further provide a carburizing prevention layer 1-2 between the main surface of the substrate 1-1 and the base layer 1-3. Moreover, it is preferable to further provide a carburization preventing layer 1-2 on the back surface of the main surface of the substrate 1-1.

  As the base material, a 40 mm square and 0.3 mm thick Fe—Ni—Cr alloy YEF426 (manufactured by Hitachi Metals, Ni 42%, Cr 6%) was used. When the surface roughness was measured using a laser microscope, the arithmetic average roughness Ra≈2.1 μm. A silicon oxide film (carburization prevention layer) having a thickness of 100 nm was formed on both the front and back surfaces of the substrate using a sputtering apparatus. Next, an alumina film (underlayer) having a thickness of 10 nm and an iron film (catalyst) having a thickness of 1.0 nm were formed on the surface only by using a sputtering apparatus. Using this base material, a base material on which a CVD was performed and an aligned CNT aggregate was grown was prepared.

  Next, separation of the aligned CNT aggregates grown on the substrate and initialization of the catalyst were performed to produce a reused substrate for producing carbon nanotubes.

  First, the grown aligned CNT aggregate was peeled from the substrate. Specifically, a plastic spatula provided with a sharp part is used, the sharp part is applied to the boundary between the aligned CNT aggregate and the base material, and the substrate surface is scraped off from the base material. The CNT aggregate orientation body was peeled off from the substrate by moving the sharp part along the axis.

Next, a catalyst initialization step was performed. The substrate after peeling the aligned CNT aggregate was set in a plasma reactor (“PR-500”; manufactured by Yamato Kagaku). Oxygen plasma treatment (conditions: pressure 10 Pa, oxygen flow rate 30 cm ³ / min, output 100 W, 60 seconds) was performed to remove carbon impurities deposited on the catalyst surface on the substrate. By this step, a catalyst initialization layer was formed on the outermost surface of the substrate. By this operation, the base material was in the state shown in FIG. 3, and a reusable base material for producing carbon nanotubes could be manufactured.

  The Raman spectrum of the substrate surface after separation of the aligned CNT aggregate and after the initialization process was measured (FIG. 4). After exfoliation of the aligned CNT aggregate, peaks considered to be carbon components are present near 1600 cm −1 and 1350 cm −1, whereas the peaks disappeared after the catalyst initialization step. This confirmed that a catalyst initialization layer comprising at least one carbon component-free catalyst fine particle was obtained.

[Example 2]
In Example 2, a carbon nanotube production substrate was manufactured from a carbon nanotube production reuse substrate.

  FIG. 2 shows an example of the base material for producing carbon nanotubes in the present invention. First, it has the base material 1-1 for carrying | supporting a catalyst. The substrate 1-1 is preferably made of a metal material. A first base layer 1-3-1 is provided on the main surface of the substrate 1-1. A catalyst initialization layer 1-4 including at least one carbon component-free catalyst fine particle is provided on the first base layer 1-3-1. A second underlayer 1-3-2 is provided on the catalyst initialization layer 1-4. A catalyst 1-5 is provided on the second underlayer 1-3-2.

  It is preferable to further provide a carburization preventing layer 1-2 between the main surface of the substrate 1-1 and the first underlayer 1-3-1. It is preferable to further provide a carburization preventing layer 1-2 on the back surface of the main surface of the substrate 1-1.

  In the reused carbon nanotube production substrate produced in Example 1, an alumina film (underlayer) having a thickness of 10 nm was produced on the catalyst initialization layer using a sputtering apparatus. Next, an iron film (catalyst) having a thickness of 1.0 nm was formed thereon using a sputtering apparatus. By this operation, the base material was in the state shown in FIG. 2, and the base material for producing carbon nanotubes could be manufactured.

[Example 3]
In Example 3, the production of the reused carbon nanotube production substrate performed in Example 1, the production of the carbon nanotube production substrate performed in Example 2, and the CVD were repeated 30 times on the same substrate. FIG. 5 shows the layer structure of the carbon nanotube production base material produced for the 30th time. FIG. 6 is a flowchart showing this process.

  About the carbon nanotube production | generation base material manufactured in Example 2, and the carbon nanotube production | generation base material manufactured by repeating 30 cycles in Example 3, it installs in a CVD furnace, CNT is grown, and evaluation of obtained CNT Carried out.

The properties of the obtained single-walled aligned CNT aggregate were of the same quality. Depending on the details of the production conditions, typical values are as follows: production rate 1.8 mg / cm ² , G / D ratio 8.0, density: 0.03 g / cm ³ , BET-specific surface area: 1200 m ² / g, average The outer diameter was 2.5 nm, the half width was 2 nm, the carbon purity was 99.9%, and the Hermann orientation coefficient was 0.7.

  From this result, it was confirmed that the same quality carbon nanotubes were grown by reusing the base material. Therefore, it can be said that the base material for reuse manufactured in Example 1 is the reuse base material for producing carbon nanotubes of the present invention.

(Substrate deformation before and after CVD)
The amount of deformation of the base material after CVD, that is, after carbon nanotube production was measured. As shown in FIG. 7, the generated base material was placed on the reference surface in a downwardly convex state, and the height from the reference surface of the base material end point was measured using a caliper as the amount of deformation. .

  Regarding the carbon nanotube production substrate produced in Example 2 and the carbon nanotube production substrate produced in Example 3, the deformation of the substrate before and after the CVD was measured, and no deformation of the substrate was observed at 0 mm. . Even after the substrate was subjected to 30 times of CVD, it is considered that the carburization prevention layer prevented carburization of the substrate and the substrate did not deform.

  FIG. 8 shows the results when reuse is performed with respect to Example 1 and Example 2 using the following three base materials. Regarding the reuse of the base material, the case where the carbon nanotube of the same quality could be stably produced was indicated by a circle, and the case where the growth of the carbon nanotube deteriorated and the base material could not be reused was indicated by the cross mark. (1) The base film and the base material on which the catalyst is laminated without carrying out the catalyst initialization step, (2) the base film on which the base film and the catalyst are not laminated on the catalyst initialization layer, (3) the catalyst The base material which did not perform the process of providing a base film and a catalyst without performing the initialization process was implemented. With the substrates of (1), (2), and (3), carbon nanotubes of the same quality could not be stably obtained, and the substrate could not be reused.

(Production equipment)
The production apparatus used for synthesizing carbon nanotubes with the carbon nanotube production substrate of the present invention must include a synthesis furnace (reaction chamber) for receiving the catalyst and the supported substrate, and heating means. There is no particular limitation on the structure and configuration of, for example, thermal CVD furnace, thermal heating furnace, electric furnace, drying furnace, thermostat, atmosphere furnace, gas replacement furnace, muffle furnace, oven, vacuum heating furnace, plasma Known reactors such as reactors, microplasma reactors, RF plasma reactors, electromagnetic heating reactors, microwave irradiation reactors, infrared irradiation heating furnaces, ultraviolet heating reactors, MBE reactors, MOCVD reactors, laser heating devices, etc. Any production equipment can be used.

  The carbon nanotube synthesis in this example used the CVD apparatus shown in FIG. This CVD apparatus is provided so as to surround the reaction chamber 2-2 having a tubular reaction chamber 2-2 (diameter 30 mm, heating length 360 mm) made of quartz glass for receiving the carbon nanotube production substrate 2-1. The heating coil 2-3, the feed pipe 2-6 connected to one end of the reaction chamber 2-2 to supply the source gas 2-4 and the atmospheric gas 2-5, and the other end of the reaction chamber 2-2 And an exhaust pipe 2-7 connected to the exhaust pipe 2 and a catalyst activator supply pipe 2-9 connected to an intermediate portion of the supply pipe 2-6 to supply the catalyst activator 2-8. In addition, in order to control and supply an extremely small amount of catalyst activator with high accuracy, the feed gas 2-4 and the atmosphere gas 2-5 are provided in the feed pipe 2-6 of the feed gas 2-4 and the atmosphere gas 2-5. A purifier 2-10 for removing the catalyst activator from the reactor is attached. Further, although not shown, a control device including a flow control valve, a pressure control valve, and the like is attached at an appropriate place.

The carbon nanotube production substrate was placed in a reaction furnace of a CVD apparatus (FIG. 9) maintained at a furnace temperature: 750 ° C. and a furnace pressure: 1.02E + 5. In this furnace, He: 100 sccm, H ₂ : 900 sccm was introduced for 6 minutes. As a result, the catalyst was reduced and the formation of fine particles in a state suitable for the growth of single-walled CNTs was promoted, and a large number of nanometer-sized catalyst fine particles were formed on the underlayer (formation process). At this time, the density of the catalyst fine particles was adjusted to 1 × 10 ¹² to 1 × 10 ¹⁴ particles / cm ² .

Next, in a reactor maintained at a furnace temperature: 750 ° C. and a furnace pressure: 1.02E + 5, He: 850 sccm, C ₂ H ₄ : 100 sccm, H ₂ O-containing He (relative humidity 23%) : 50 sccm was supplied for 5 minutes. Thereby, single-walled CNT grew from each catalyst fine particle (growth process).

  After the growth process was completed, only He: 1000 sccm was supplied into the reaction furnace, and the remaining raw material gas and catalyst activator were removed (flash process). Thereby, the aligned carbon nanotube aggregate 2-11 was obtained.

  The present invention can be used suitably in the fields of electronic device materials, optical element materials, conductive materials, and the like because an aligned CNT aggregate can be repeatedly produced with high production efficiency using a single substrate.

1-1 Substrate 1-2 Carburization Prevention Layer 1-3 Underlayer 1-3-1 First Underlayer 1-3-2 Second Underlayer 1-4 Catalyst Initialization Layer 1-5 Catalyst 1-6 Carbon impurities on catalyst surface 2-1 Substrate for carbon nanotube production 2-2 Reaction chamber 2-3 Heating coil 2-4 Source gas 2-5 Atmospheric gas 2-6 Supply pipe 2-7 Exhaust pipe 2-8 Catalyst activator 2-9 Catalyst activator supply pipe 2-10 Purifier

Claims (10)

A substrate;
An underlayer provided on the surface of the base material and serving as an underlayer for the catalyst;
A catalyst initialization layer provided on the surface of the underlayer, on the surface opposite to the substrate, and comprising at least one catalyst fine particle not containing a carbon component;
The provided, arithmetic mean roughness Ra is recycled substrate Carbon Nanotubes Ru der below 3μm on the surface of the substrate.   The said base material consists of metals, The reuse base material for carbon nanotube production | generation of Claim 1 characterized by the above-mentioned.   3. The carbon nanotube production device according to claim 1, further comprising a carburization prevention layer that prevents a carbon component from penetrating into the base material between the base material and the base layer. 4. Reusable substrate.   The carburization prevention layer which prevents that a carbon component penetrate | infiltrate into the said base material is provided in the surface of the said base material, and the surface on the opposite side to the side in which a base layer is located. 4. The reuse base material for producing carbon nanotubes according to any one of items 1 to 3. A peeling step of peeling carbon nanotubes formed on the catalyst layer on the substrate from the catalyst layer;
An initialization step of initializing the catalyst fine particles by removing carbon components from the catalyst fine particles remaining in the catalyst layer;
Unrealized method of arithmetic average roughness Ra is recycled substrate for generating carbon nanotubes is 3μm or less of the surface of the base material. A substrate;
A first underlayer provided on the surface of the base material and serving as a base of the catalyst;
A catalyst layer provided on the surface opposite to the base material on the surface of the base layer, the catalyst layer including at least one catalyst fine particle not containing a carbon component;
A second underlayer serving as a catalyst underlayer provided on the catalyst layer on the side opposite to the first underlayer;
A catalyst provided on the second underlayer;
The provided, arithmetic mean roughness Ra of 3μm or less der Ru carbon nanotubes produced base material for a surface of the substrate.   The said base material consists of metals, The base material for carbon nanotube production | generation of Claim 6 characterized by the above-mentioned.   8. The carbon nanotube production device according to claim 6, further comprising a carburization prevention layer that prevents a carbon component from penetrating into the base material between the base material and the first underlayer. 9. Base material.   The carburization prevention layer which prevents that a carbon component osmose | permeates the said base material is further provided in the surface on the said base material, and the surface on the opposite side to the side in which a base layer is located from Claim 6 characterized by the above-mentioned. 9. The carbon nanotube production substrate according to any one of 8 above. A peeling step of peeling carbon nanotubes formed on the catalyst layer on the substrate from the catalyst layer;
An initialization step of initializing the catalyst fine particles by removing carbon components from the catalyst fine particles remaining in the catalyst layer;
On the catalyst layer that has been initialized, a base layer forming step of providing a base layer serving as a base for the catalyst on the side opposite to the base material;
A catalyst forming step of providing a catalyst on the base layer opposite to the catalyst layer;
Unrealized method of arithmetic average roughness Ra of the carbon nanotube generation substrate is 3μm or less of the surface of the base material.

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