WO2019107362A1

WO2019107362A1 - Carbon nanotube growth substrate and carbon nanotube production method

Info

Publication number: WO2019107362A1
Application number: PCT/JP2018/043615
Authority: WO
Inventors: 健司水田
Original assignee: 日立造船株式会社
Priority date: 2017-11-30
Filing date: 2018-11-27
Publication date: 2019-06-06
Also published as: JPWO2019107362A1; TW201925084A; JP7060614B2

Abstract

The purpose of the present invention is to not cause cracking in an intermediary layer when heating a carbon nanotube growth substrate to a carbon nanotube growth temperature, even when heating at a high heating rate. This carbon nanotube growth substrate (1) is provided with a base material (2) formed from a metal, a silica layer (3) formed on the surface of the base material (2) and containing silicon oxide, and a catalyst layer (4) formed on the surface of the silica layer (3) opposite the side of the base material (2). Represented by the compositional formula SiOx, the siliconoxide in the silica layer (3) has an x value less than 2.

Description

Substrate for growth of carbon nanotube and method of manufacturing carbon nanotube

The present invention relates to a carbon nanotube growth substrate and the like used for producing carbon nanotubes.

Carbon nanotubes are attracting attention as materials having excellent electrical conductivity, thermal conductivity, and mechanical strength, and have been used in various fields. Chemical vapor deposition (CVD) is used as a method for producing carbon nanotubes. For example, in Patent Document 1 and Patent Document 2, a catalyst layer formed on the surface of the metal base, the intermediate layer made of aluminum, silicon, silicon dioxide or the like and the surface of the intermediate layer opposite to the substrate side is disclosed. It is disclosed that carbon nanotubes are produced by a CVD method using a carbon nanotube growth substrate provided with

"Japanese Published Patent Application Publication No. 2007-70137" "Japanese Published Patent Application Publication No. 2013-1598"

However, in the techniques disclosed in Patent Document 1 and Patent Document 2, the intermediate layer is made of aluminum, silicon, silicon dioxide or the like. Therefore, when heating the substrate for carbon nanotube growth to the growth temperature of carbon nanotubes, if the substrate is heated at a high temperature rising rate (for example, 400 ° C./min or more), rapid thermal expansion of the metal serving as the substrate A crack occurs in the intermediate layer (see FIG. 12). As a result, in the carbon nanotube growth substrate in which the crack is generated, a defect is generated in the carbon nanotube to be manufactured in the portion where the crack is generated, and the carbon nanotube can not be favorably manufactured. That is, in the techniques of Patent Document 1 and Patent Document 2, there is a problem that the substrate for carbon nanotube growth needs to be heated to the growth temperature of carbon nanotubes at a low temperature rising rate, and the productivity is low.

One aspect of the present invention is to realize a carbon nanotube growth substrate which does not generate cracks in the intermediate layer even when heated at a high temperature rising rate when heating the carbon nanotube growth substrate to the growth temperature of carbon nanotubes. To aim.

In order to solve the above-mentioned subject, a substrate for carbon nanotube growth concerning one mode of the present invention is a substrate which consists of metals, an intermediate layer which is formed on a surface of the substrate, and contains silicon oxide, and the intermediate layer. And a catalyst layer formed on the surface opposite to the substrate side, and the silicon oxide in the intermediate layer has a value of x smaller than 2 when represented by the composition formula SiO _x .

According to one aspect of the present invention, there is provided a carbon nanotube growth substrate which does not generate cracks in the intermediate layer even when heated at a high temperature rise rate when heating the carbon nanotube growth substrate to the growth temperature of carbon nanotubes. It plays an effect.

FIG. 1 is a cross-sectional view showing the configuration of a carbon nanotube growth substrate according to Embodiment 1 of the present invention. (A) is a structural view of silicon dioxide (SiO ₂ ), and (b) is a structural view of silicon oxide constituting a silica layer provided in the substrate for carbon nanotube growth. It is a graph which shows the measurement result of the binding energy of the Si2p orbital of the conventional silica layer by XPS, and the measurement result of the binding energy of the Si2p orbital of the silica layer concerning Embodiment 1 by XPS. 5 is a flowchart showing an example of the process of the method for producing a carbon nanotube according to the first embodiment. FIG. 1 is a schematic view of a carbon nanotube production apparatus according to Embodiment 1. It is a graph which shows the measurement result of the binding energy of the Si2p track of the silica film in the substrate for carbon nanotube growth as an example of the present invention. It is a graph which shows the measurement result of the binding energy of the Si2p orbit of the silica film in the substrate for carbon nanotube growth as a comparative example of the present invention. It is a table | surface which shows the experimental result in 1st Example. It is a figure which shows the mode of the surface after the heating experiment of the board | substrate for carbon nanotube growth as said comparative example. It is a figure which shows the mode of the surface after the heating experiment of the board | substrate for carbon nanotube growth as the said Example. It is a table | surface which shows the experimental result in 2nd Example. It is an enlarged view which shows the state of the surface of the conventional substrate for carbon nanotube growth.

Embodiment 1
Hereinafter, the carbon nanotube growth substrate 1 according to one aspect of the present invention will be described in detail. Below, a carbon nanotube is abbreviated as "CNT."

(Structure of substrate 1 for carbon nanotube growth)
FIG. 1 is a cross-sectional view showing the configuration of a CNT growth substrate 1. As shown in FIG. 1, the CNT growth substrate 1 includes a base material 2, a silica layer 3 (intermediate layer), a catalyst layer 4, and a backing layer 5.

The substrate 2 is a thin film made of metal. The substrate 2 needs to be a metal having heat resistance so as not to be deformed by the high temperature in the heating step and the CNT growth step described later. Specifically, a metal foil of stainless steel is preferable, and a metal foil of ferritic stainless steel (for example, SUS444) having a small thermal expansion coefficient is more preferable.

The substrate 2 preferably has a pliable thickness so that it can be rolled in the production of CNTs described later. Specifically, when the substrate 2 is made of ferritic stainless steel, the thickness of the substrate 2 is preferably 10 to 500 μm in order to maintain flexibility. The surface roughness of the substrate 2 is preferably 0.2 to 1 μm. When the surface roughness Ra of the base material 2 is larger than 1 μm, the surface roughness of the catalyst layer 4 described later becomes large, and the CNT can not be favorably manufactured. In addition, even if the surface roughness Ra of the base material 2 is smaller than 0.2 μm, there is no great effect, and the processing cost such as polishing becomes large.

The silica layer 3 is a layer formed on the surface on one side of the substrate 2 and containing silicon oxide (SiO _x ). The silica layer 3 is a layer for preventing diffusion of a component such as Cr from the base material 2 to the catalyst layer 4 described later. When a component such as Cr from the base material 2 diffuses into the catalyst layer 4, the diffused atoms react with the metal constituting the catalyst layer 4 and the catalytic function of the catalyst layer 4 is degraded. Further, by forming the silica layer 3 on the CNT growth substrate 1, the surface of the CNT growth substrate 1 can be made flat. As a result, micronization of the catalyst metal of the catalyst layer 4 can be promoted.

The silica layer 3 in the present embodiment is made of silicon oxide (SiO _x ) having a lower oxygen content than silicon dioxide (SiO ₂ ). In other words, the silicon oxide in the silica layer 3 has a value of x smaller than 2 when represented by the composition formula SiO _x . (A) of FIG. 2 is a structural view of silicon dioxide (SiO ₂ ), and (b) is a structural view of silicon oxide constituting the silica layer 3 of the present embodiment.

As shown in (a) of FIG. 2, silicon dioxide is a regular tetrahedral structure in which substantially all O atoms are bonded to two Si atoms. On the other hand, the silicon oxide constituting the silica layer 3 of the present embodiment has a lower bonding ratio of Si atoms to O atoms than silicon dioxide as shown in FIG. Voids are formed in the structure. By having the crystal structure, the silicon oxide of the silica layer 3 is more stretchable than silicon dioxide (in other words, the rigidity is lower). Therefore, the silica layer 3 can expand and contract following the thermal expansion of the base material 2 due to a rapid temperature rise (specifically, a temperature rise of 700 ° C./minute or less) in the heating step described later. Thereby, in the substrate 1 for CNT growth, it can prevent that a crack is formed in the silica layer 3 in a heating process. As a result, in the substrate for CNT growth 1, CNTs can be favorably grown. The silicon oxide constituting the silica layer 3 has a value of x of 0.2 when it is expressed by the composition formula SiO _x so that it can be followed by the thermal expansion of the base material 2 due to a rapid temperature rise in the heating step. It is preferable that it is above 1.4 and below.

FIG. 3 shows the measurement results of the bond energy of Si2p orbitals of the conventional silica layer by XPS (X-ray photoelectron spectroscopy) and the measurement results of the bond energy of the Si2p orbital of one example of the silica layer of the present invention by XPS. It is a graph. As shown in FIG. 3, the peak position of the binding energy of Si in the silica layer of the present invention, the binding energy of Si in SiO ₂ (i.e., the binding energy of Si in case of SiO ₂₎ is lower than the peak position of the ing. That is, the silica layer of the present invention, at least a part of Si is not the SiO _2, constitute the degree of oxidation is small silicon oxide than SiO _2.

The film thickness of the silica layer 3 is preferably 150 to 1500 nm. When the film thickness of the silica layer 3 is larger than 1500 nm, cracks easily occur in the silica layer 3 during high temperature treatment (specifically, a heating step and a CNT growth step described later). In addition, if the film thickness of the silica layer 3 is smaller than 150 nm, components such as Cr from the base material 2 diffuse into the catalyst layer 4 described later, and the catalyst metal of the catalyst layer 4 can not be finely divided. It is not preferable because it

The catalyst layer 4 is a layer formed on the surface of the silica layer 3 opposite to the substrate 2 side. The catalyst layer 4 is a layer containing a metal. The metal is preferably selected from the group consisting of iron, cobalt, nickel and alloys of these metals. The film thickness of the catalyst layer 4 is 0.1 to 10 nm.

The backing layer 5 is a layer formed on the surface of the base 2 opposite to the surface on which the silica layer 3 is formed. The backing layer 5 is made of silicon oxide having the same composition as the silicon oxide constituting the silica layer 3. When the backing layer is not formed in the CNT growth substrate, the CNT growth substrate is bent due to the difference in the thermal expansion coefficient between the base and the silica layer in the heating step and the CNT growth step described later. On the other hand, by forming the backing layer 5, layers composed of silicon oxide are formed on both sides of the base material 2, so the substrate for CNT growth 1 is bent in the heating step and the CNT growth step. Can be suppressed. In order to suppress bending of the substrate for CNT growth 1 in the heating step and the CNT growth step, it is preferable to set the difference between the film thickness of the backing layer 5 and the film thickness of the silica layer 3 to 100 nm or less. In one aspect of the present invention, a catalyst layer may be formed on the backing layer 5 to manufacture CNTs on both sides of the CNT growth substrate.

(Method of manufacturing substrate 1 for carbon nanotube growth)
The manufacturing process of the substrate for CNT growth in the present embodiment includes a silicon oxide film forming process and a catalyst layer forming process.

The silicon oxide film forming step is a step of forming the silica layer 3 on one surface of the substrate 2 and forming the backing layer 5 on the other surface of the substrate 2. Since the process of forming the silica layer 3 is the same as the process of forming the backing layer 5, the process of forming the silica layer 3 will be described here.

In the step of forming the silica layer 3 in the present embodiment, a solution method is used. Specifically, first, a precursor to be a raw material of the silica layer 3 is applied to the substrate 2. The precursor includes ethyl polysilicate (partial hydrolytic condensate of tetraethoxysilane) and methyltriethoxysilane (an alkyl alkoxysilane) (a compound in which a part of ethyl groups of ethyl polysilicate is substituted with a methyl group) In a predetermined ratio. Specifically, the predetermined ratio is a ratio of 150 to 900 g of methyltriethoxysilane to 100 g of ethyl polysilicate.

Next, the precursor applied to the substrate 2 is baked at 500 to 700 ° C. for 5 to 60 minutes. This cures the precursor and completely removes the solvent and moisture remaining in the precursor. As a result, the silica layer 3 is formed on the surface of the substrate 2.

Here, as described above, the precursor in the present embodiment includes ethyl polysilicate and methyl triethoxysilane. Ethyl polysilicate becomes silicon dioxide SiO ₂ by being fired. On the other hand, methyltriethoxysilane becomes silicon oxide by being fired, but no Si—O—Si bond is formed at the location corresponding to the methyl group (in other words, the crosslinking reaction of silica does not occur). Therefore, the silica layer 3 in the present embodiment is made of silicon oxide having a lower oxygen content than silicon dioxide.

In addition, although it is an aspect using ethyl polysilicate and methyl triethoxysilane as a precursor in this embodiment, it is not restricted to this. In one aspect of the present invention, methyl polysilicate may be used as a precursor instead of ethyl polysilicate. As a precursor, instead of ethylpolysilicate, tetraethoxysilane or tetramethoxysilane which is a monomer may be used. Also, in one aspect of the present invention, instead of methyltriethoxysilane, a substance substituted with another functional group such as methyltrimethoxysilane may be used.

Moreover, in this embodiment, although it was an aspect which forms the silica layer 3 and the backing layer 5 using a solution method, it is not restricted to this. That is, if the silicon oxide constituting the silica layer 3 and the backing layer 5 is silicon oxide having a lower oxygen content than silicon dioxide, the silica layer 3 and the backing layer 5 may be formed using other methods. For example, vapor deposition or sputtering may be used to form the silica layer 3 and the backing layer 5. When vapor deposition or sputtering is used, a SiO target or raw material may be used, or a mixed target of SiO and SiO ₂ may be used.

The catalyst layer forming step is a step of forming the catalyst layer 4 on the surface of the silica layer 3 opposite to the substrate 2 side. In the catalyst layer forming step, a thin metal film is formed on the surface of the silica layer 3 on the opposite side to the base 2 side using a conventional method such as EB (electron beam, electron beam) method, sputtering method or solution method. Process.

(Manufacturing method of carbon nanotube using substrate 1 for carbon nanotube growth)
FIG. 4 is a flowchart showing an example of processing of the method for producing CNT in the present embodiment. FIG. 5 is a schematic view of a CNT manufacturing apparatus 30. As shown in FIG.

As shown in FIG. 4, the method for producing CNTs in the present embodiment includes a heating step (S1), a CNT growth step (S2, a growth step), and a post-treatment step (S3). Further, as shown in FIG. 5, the CNT manufacturing apparatus 30 includes a substrate supply chamber 31, a heating chamber 32, a reaction chamber 33, a post-processing chamber 34, a substrate winding chamber 35, and a heater 36. There is.

The heating step is a step of heating the CNT growth substrate 1 delivered from the substrate unwinding device 31 A of the substrate supply chamber 31 to the heating chamber 32 to a CNT growth temperature of 600 to 700 ° C. using the heater 36. As shown in FIG. 5, the heating chamber 32 includes a chamber 32A and a gas supply port 32B for supplying a gas to the chamber 32A. In the heating step, while the inside of the chamber 32A is maintained at a predetermined degree of vacuum (several Pa to 10000 Pa), a gas (specifically, acetylene gas (C ₂ H ₂ )) containing no oxygen is The substrate for CNT growth 1 is heated while being supplied to the chamber 32A. In the heating step in the present embodiment, the temperature of the CNT growth substrate 1 is raised at a temperature rising rate of 200 to 700 ° C./min.

As described above, the silicon oxide of the silica layer 3 in the present embodiment is more stretchable than silicon dioxide. Therefore, even if the substrate 1 for CNT growth is heated at a high temperature rising rate of 200 to 700 ° C./min, preferably 500 to 700 ° C./min, the silica layer 3 follows the thermal expansion of the substrate 2 It can be expanded and contracted. As a result, formation of a crack in the silica layer 3 can be prevented.

The CNT growth step is a step of growing (producing) CNT on the surface of the catalyst layer 4 of the substrate for CNT growth 1 which is heated to the CNT growth temperature in the heating step and sent out to the reaction chamber 33. As shown in FIG. 5, the reaction chamber 33 includes three chambers 33A, and a gas supply port 33B for supplying a gas to each chamber 33A.

The interior of the chamber 33A is maintained at the CNT growth temperature by the heater 36. In the CNT growth step, CNTs are produced by a chemical vapor deposition (CVD) method. Specifically, while maintaining the inside of the chamber 33A at a predetermined degree of vacuum (several Pa to 10000 Pa), a raw material gas (for example, acetylene, methane, butane or the like may be used) for the formation of CNTs is supplied to the gas supply port 33B. To the chamber 33A. Thereby, CNTs are formed starting from the catalyst fine particles on the surface of the catalyst layer 4.

The post-treatment step is a step of cooling the CNT growth substrate on which the CNTs are formed in the CNT growth step in the post-treatment chamber 34 and inspecting the formed CNTs. After the post-processing step, the CNT growth substrate 1 is transported to the substrate winding chamber 35, the protective film is attached to the upper surface thereof, and wound around the substrate winding device 35A provided in the substrate winding chamber 35. To be taken. That is, the substrate 1 for CNT growth on which CNTs are formed is collected as a product.

As described above, the CNT growth substrate 1 in the present embodiment includes the base material 2, the silica layer 3, the catalyst layer 4 and the backing layer 5, and the silica layer 3 is more than silicon dioxide (SiO ₂ ). It is composed of silicon oxide (SiO _x ) having a low content of oxygen (in other words, the silicon oxide in the silica layer 3 has a value of x smaller than 2 when represented by the composition formula SiO _x ). Thereby, even if it heats at a rapid temperature rising rate in a heating process, the silica layer 3 can be expanded and contracted following the thermal expansion of the base material 2. As a result, no crack is formed, and CNT can be favorably grown in the CNT growth step.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

First Embodiment
Examples of the invention are described below. In the first example, Examples 1 to 5 as Examples of the CNT growth substrate of the present invention and Comparative Example 1 as Comparative Example of the CNT growth substrate of the present invention will be described.

The CNT growth substrate of Example 1 was produced as follows. First, a solution was prepared by mixing 40 g of ethyl polysilicate (ethyl silicate 45, manufactured by Tama Chemical Co., Ltd., average molecular weight 1000) and 60 g of methyltriethoxysilane (manufactured by Tama Co., Ltd., average molecular weight 178). Next, 131.4 g of ethanol was mixed with this solution. Next, 113.6 g of water and a small amount of hydrochloric acid as a catalyst for accelerating the hydrolysis reaction of silica were added to this solution. After the addition, the mixture was stirred for about one day to prepare a precursor solution of silica.

Next, the precursor solution was applied by roll coating on both sides of a stainless steel thin film (substrate 2 of the present invention) having a width of 400 mm and a thickness of 50 μm, and dried at 300 ° C. for about 10 minutes. Next, by baking for about 15 minutes at 600 ° C., a silica film (the silica layer 3 and the backing layer 5 of the present invention) having a thickness of 400 nm was formed on both sides of the stainless steel thin film. Next, a thin film of Fe of 5 nm (the catalyst layer 4 of the present invention) was formed on one surface of the silica film by an EB method, to prepare a substrate for CNT growth.

In the preparation of a precursor solution of silica, the substrate for CNT growth of Example 2 comprises 35 g of ethyl polysilicate (ethyl silicate 45, manufactured by Tama Chemical Co., average molecular weight 1000) and 65 g of methyltriethoxysilane (Tama Chemical Co., Ltd.) The CNT growth substrate of Example 1 was manufactured in the same manner as in Example 1 except that an average molecular weight of 178), 216.6 g of ethanol and 28.4 g of water were used.

In the preparation of a precursor solution of silica, the substrate for CNT growth of Example 3 comprises 30 g of ethyl polysilicate (ethyl silicate 45, manufactured by Tama Chemical Co., average molecular weight 1000) and 70 g of methyltriethoxysilane (Tama Chemical Co., Ltd.) The CNT growth substrate of Example 1 was manufactured in the same manner as in Example 1 except that an average molecular weight of 178), 234.4 g of ethanol and 10.7 g of water were used.

In the preparation of a precursor solution of silica, the CNT growth substrate of Example 4 comprises 30 g of ethyl polysilicate (ethyl silicate 45, manufactured by Tama Chemical Co., average molecular weight 1000) and 70 g of methyltriethoxysilane (Tama Chemical Co., Ltd.) The CNT growth substrate of Example 1 was manufactured in the same manner as in Example 1 except that an average molecular weight of 178), 239.3 g of ethanol and 5.7 g of water were used.

In the preparation of a precursor solution of silica, the substrate for CNT growth of Example 5 comprises 10 g of ethyl polysilicate (ethyl silicate 45, manufactured by Tama Chemicals Co., average molecular weight 1000) and 90 g of methyltriethoxysilane ( The CNT growth substrate of Example 1 was manufactured in the same manner as in Example 1 except that an average molecular weight of 178), 241.4 g of ethanol and 3.6 g of water were used.

The substrate for CNT growth of Comparative Example 1 was prepared by mixing 100 g of ethyl polysilicate (ethyl silicate 45, manufactured by Tama Chemicals Co., Ltd., average molecular weight of 1000), 131.4 g of ethanol, and 113.6 g in the preparation of a precursor solution of silica. Were prepared in the same manner as in the method for producing a substrate for CNT growth of Example 1 except that the following water and water were used.

FIG. 6 is a graph showing the measurement results of the bonding energy of the Si2p orbit of the silica film in the substrate for CNT growth of Examples 1 to 5. FIG. 7 is a graph showing the measurement results of the bonding energy of the Si2p orbit of the silica film in the substrate for CNT growth of Comparative Example 1. As shown in FIG. 7, in the silica film of the substrate for CNT growth of Comparative Example 1, the peak position of the Si binding energy was approximately the position of SiO ₂ . That is, the silica film of the substrate for CNT growth of Comparative Example 1 was made of SiO ₂ . On the other hand, in the silica film in the CNT growth substrate of Examples 1 to 5, as shown in FIG. 6, the peak position of the Si binding energy was lower than the position of SiO ₂ . In other words, the silica film in the CNT growth substrate of Examples 1-5, at least a part of Si in SiO ₂ rather than SiO ₂ were composed oxidation degree is small silicon oxide.

The value of _x in the composition formula SiO _x of the silica film of the substrate for CNT growth of Examples 1 to 5 was calculated from the measurement results of XPS shown in FIG. As a result, the values (peak values) of _x in the composition formula SiO _x of the silica film of the CNT growth substrate of Examples 1 to 5 are 1.7, 1.4, 0.9, 0.5, 0, respectively. It was .2. That is, in the measurement results of XPS, the value (peak value) of _x in the composition formula SiO _x of the silica film of the substrate for CNT growth was smaller than 2.

Next, results of heating experiments in which the substrates for CNT growth of Examples 1 to 5 and Comparative Example 1 are heated at a high temperature rising rate will be described. In this heating experiment, the substrate for CNT growth was heated to 700 ° C. at a temperature rising rate of 300 to 700 ° C./min to confirm whether or not a crack was generated in the silica film of the substrate for CNT growth. The experimental results are shown in FIG. Here, “o” in the table shown in FIG. 8 indicates that no crack was generated in the silica film, and “Δ” indicates that a crack to a degree that causes no problem in growing CNT well was generated. "X" shows that the crack which can not make CNT grow favorably generate | occur | produced.

As shown in FIG. 8, in the silica film of the substrate for CNT growth of Comparative Example 1, cracks can not be grown well when heated at a temperature rising rate of 600 ° C./min or 700 ° C./min. Occurred. On the other hand, in the silica film of the substrate for CNT growth of Examples 1 to 5, even when heated at a temperature rising rate of 700 ° C./min, cracks are generated only to the extent that there is no problem in growing CNT. I did not. This is because the silica film in the substrate for CNT growth of Examples 1 to 5 comprises silicon oxide in which at least a part of Si has a smaller degree of oxidation than SiO ₂ , the silica film follows the thermal expansion of the stainless steel thin film It is thought that it was because it was able to expand and contract. In particular, in the silica film of the substrate for CNT growth of Examples 2 to 5, since the stretchability of silicon oxide is high, no crack was generated even when heated at a temperature rising rate of 700 ° C./min.

FIG. 9 is a view showing the appearance of the surface of the CNT growth substrate of Comparative Example 1 after the heating experiment. FIG. 10 is a view showing the appearance of the surface of the substrate for CNT growth of Example 2 after a heating experiment. In the substrate for CNT growth of Comparative Example 1, as shown in FIG. 9, cracks were generated on the surface after the heating test. On the other hand, in the substrate for CNT growth of Example 2, as shown in FIG. 10, no crack was generated even after the heating test.

Second Embodiment
In the second embodiment, an embodiment in which the film thickness of the silica film (the silica layer 3 and the backing layer 5 of the present invention) is changed will be described. The substrate for CNT growth in the second example was produced in the same procedure as the substrate for CNT growth in example 3 in the first example except that the film thickness of the silica film was changed. That is, in the substrate for CNT growth in the second embodiment, _x in the silicon oxide SiO _x forming the silica film was 0.9. In the second embodiment, the thickness of the silica film was changed from 50 nm to 2500 nm by changing the amount of application of the precursor solution of the silica film to the stainless steel thin film.

In the second embodiment, CNTs were produced using the produced CNT growth substrate, and the orientation length of the CNTs, the bulk density, and the presence or absence of cracks in the CNT growth substrate were evaluated. The orientation length of the CNT was evaluated by the average value of three measurements performed by performing laser scanning three times in the width direction of the substrate for CNT growth. The bulk density of CNT was calculated by measuring the weight of the exfoliated CNT after exfoliating the CNT produced using the adhesive tape.

The procedure for producing the CNT in the second embodiment is as follows. First, the substrate for CNT growth was heated to 680 ° C. at a heating rate of 600 ° C./min while supplying nitrogen gas into the chamber. Next, CNT was grown (made) while supplying acetylene gas into the chamber while maintaining the temperature at 680 ° C.

FIG. 11 is a table showing experimental results in the second embodiment. As shown in FIG. 11, in the substrate for CNT growth in which the film thickness of the silica film is 50 to 1500 nm, no crack was generated in the silica film. On the other hand, in the substrate for CNT growth in which the film thickness of the silica film is 2000 to 2500 nm, a crack was generated in the silica film. The occurrence of the crack is not due to the high temperature rising rate, but is due to the silica film being peeled off from the stainless steel thin film when the substrate for CNT growth is brought to a high temperature because the silica film is too thick. Conceivable.

Moreover, in the substrate for CNT growth with a film thickness of 50 to 100 nm of silica film, although the crack did not occur in the silica film, the orientation length and bulk density of the produced CNT were manufactured using other substrates for CNT growth. It was less than the oriented length and bulk density of the resulting CNTs, and was not desirable as a product. It is considered that this is because, since the film thickness of the silica film is too small, a component such as Cr diffuses from the stainless steel thin film to the thin film of Fe which is a catalyst layer, and Fe as a catalyst can not be micronized.

1 substrate for carbon nanotube growth 2 substrate 3 silica layer (intermediate layer)
4 catalyst layer 5 backing layer

Claims

A substrate made of metal,
An intermediate layer formed on the surface of the substrate and containing silicon oxide;
A catalyst layer formed on the surface of the intermediate layer opposite to the substrate side,
The substrate for carbon nanotube growth, wherein the silicon oxide in the intermediate layer has a value of x smaller than 2 when represented by a composition formula SiO x .
The substrate for carbon nanotube growth according to claim 1, wherein the silicon oxide in the intermediate layer has a value of x of 0.2 or more and 1.4 or less when represented by a composition formula SiO x .
On the surface of the substrate opposite to the surface on which the intermediate layer is formed, a backing layer containing silicon oxide having the same composition as the silicon oxide contained in the intermediate layer is formed. The substrate for carbon nanotube growth according to Item 1 or 2.
The carbon nanotube growth substrate according to any one of claims 1 to 3, wherein the film thickness of the intermediate layer is 150 nm or more and 1500 nm or less.
A method of producing a carbon nanotube using the substrate for carbon nanotube growth according to any one of claims 1 to 4,
Heating the carbon nanotube growth substrate to a carbon nanotube growth temperature at a temperature rising rate of 700 ° C./min or less;
And supplying a source gas to the carbon nanotube growth substrate heated to the carbon nanotube growth temperature after the heating step, and growing carbon nanotubes on the carbon nanotube growth substrate. Of producing carbon nanotubes.