WO2008007750A1

WO2008007750A1 - Process for producing carbon nanostructure and gas for carbon nanostructure production

Info

Publication number: WO2008007750A1
Application number: PCT/JP2007/063928
Authority: WO
Inventors: Supriya Chakrabarti; Yoshikazu Nakayama; Lujun Pan; Takeshi Nagasaka; Toru Sakai
Original assignee: Osaka Industrial Promotion Organization; Public University Corporation Osaka Prefecture University; Taiyo Nippon Sanso Corporation
Priority date: 2006-07-13
Filing date: 2007-07-12
Publication date: 2008-01-17
Also published as: JP2009227470A

Abstract

A process for carbon nanostructure production in which the length of the nanostructure can be continuously regulated. The process comprises feeding a carrier gas and a raw-material gas to a reaction chamber (4) to produce a carbon nanostructure (2) by the action of a catalyst (6), wherein a reducing gas, e.g., hydrogen, which has the ability to reduce the raw-material gas is incorporated into the carrier gas or raw-material gas and an oxidizing gas, e.g., water, which has the ability to oxidize the raw-material gas is further incorporated thereinto while adequately regulating the concentrations of the reducing gas and oxidizing gas. Thus, a carbon nanostructure of good quality can be produced at a high efficiency. The process enables the production of a carbon nanotube having an overall length of, e.g., 7 mm, which has not been obtained so far. Consequently, the mechanism of the continuous growth of a carbon nanostructure can be optimized and a carbon nanostructure of high quality can be produced. Also provided is a gas for carbon nanostructure production which is for use in producing a carbon nanostructure.

Description

Specification

Carbon nanostructure manufacturing method and carbon nanostructure manufacturing gas

[0001] The present invention relates to a method for producing a carbon nanostructure such as a carbon nanotube or carbon nanocoil, and a gas for producing the carbon nanostructure. In particular, when carbon nanostructures are grown using a catalyst disposed in the reaction chamber by supplying a raw material gas and a carrier gas to the reaction chamber, a reducing gas and an oxidizing gas are further supplied to the reaction chamber. The present invention relates to a production method for efficiently synthesizing continuously growing carbon nanostructures, and a production gas used therefor.

Background art

[0002] As a method for producing a carbon nanostructure, a chemical vapor deposition method (CVD method, chemical vapor deposition) in which a raw material gas such as hydrocarbon is decomposed to grow a target material, or the above CVD method is used. As one form, a catalytic chemical vapor deposition method (CCVD method, Catalyst Chemical Vapor Deposition) is known in which a target substance is grown using a catalyst.

[0003] Conventionally, in order to produce carbon nanostructures by the CVD method, a mixed gas of a source gas and a carrier gas is introduced into a reaction chamber, the source gas is decomposed by a catalyst, and the carbon nanostructure is grown on the catalyst surface. A manufacturing method is adopted.

[0004] One of the manufacturing apparatuses using this type of manufacturing method is a raw material spray type carbon nanostructure synthesis apparatus. For example, as shown in Patent Document 1, this carbon nanostructure synthesis apparatus supplies a raw material gas together with a carrier gas to a reaction chamber in which a catalyst body is disposed, and carbon nanostructures on the surface of the catalyst body. The structure is configured to grow. The nozzle tip of the raw material gas nozzle that introduces the raw material gas into the reaction chamber is disposed near the surface of the catalyst body, and a large amount of preheated carbon raw material gas is instantaneously blasted or blown onto the catalyst surface. In addition, the carbon nanostructure can be produced with high efficiency by dramatically increasing the contact probability between the source gas and the catalyst surface.

[0005] In Non-Patent Document 1, the growth of carbon nanostructures was realized with high efficiency by supplying the necessary amount of source gas instantaneously without initial fluctuation of the source gas flow rate. In addition, carbon nano It is described that the growth mechanism of the structure has a first stage in which carbon nanostructures grow rapidly in the early stage and a second stage in which relatively slow and continuous growth occurs.

[0006] Further, Patent Document 2 discloses that a substrate having a catalytic metal layer is processed by a CVD method at a predetermined temperature with a mixing ratio of a reducing gas and a source gas within a predetermined range. A method for producing carbon nanotubes with a fiber length of 700 m or more is disclosed. By containing a reducing gas in the raw material gas, adhesion of carbon deposits to the carbon nanotubes is suppressed, and long carbon Attempts have been made to produce nanotubes.

[0007] Further, Patent Document 3 discloses a method for producing a carbon material while controlling the ratio of impurity carbon decomposition products that decompose impurity carbon generated during the growth of the carbon material. Attempts have been made to promote the growth of carbon nanotubes by decomposing impurity carbon that grows on the surface of the catalyst by allowing the carbon to be present in the vicinity of the catalyst.

Patent Document 1: Japanese Published Patent Publication “Japanese Unexamined Patent Publication No. 2004-182573 (Publication Date: July 2, 2004)”

Patent Document 2: Japanese Patent Publication “JP-A-2006-69805 (Publication Date: March 16, 2006)”

Patent Document 3: Japanese Patent Publication “JP 2006-143515 Publication (Publication Date: June 8, 2006)”

Non-Patent Document 1: Emperor Sukane, Takeshi Nagasaka, Toshinori Nosaka, Yoshiaki Nakayama, Applied Physics 13, 73rd, (20 04), No. 5

Disclosure of the invention

[0008] As described above, when the rapid growth of the carbon nanostructure in the first stage slows down, the process proceeds to the second stage where the growth is moderate. However, in the second stage above, the growth rate of carbon nanostructures is slow, so that excessively generated carbon derived from the source gas is deposited on the catalyst surface, causing a phenomenon that prevents contact between the source gas and the catalyst surface. .

[0009] For example, in the conventional carbon nanostructure manufacturing method such as the carbon nanostructure manufacturing method according to Patent Document 1 and Non-Patent Document 1 described above, the second stage is carbon diffusion rate-limiting on the catalyst surface. Finally, there was a problem that the growth of carbon nanostructures stopped. The Furthermore, the method according to Non-Patent Document 1 shows that the inventors of the present invention have a detrimental adverse effect on the synthesis part (growth in the first stage) in which the growth time of the carbon nanostructure is extremely short. This has already been clarified by research.

[0010] In addition, the carbon nanotubes produced by the methods disclosed in Patent Documents 2 and 3 each have a maximum length of 1000 / ζ πι and about 2.5 mm, and are not yet sufficiently long. Therefore, the methods disclosed in Patent Documents 2 and 3 have a problem that efficient production of carbon nanotubes has not yet been realized. This is presumed to be caused by the methods disclosed in Patent Documents 2 and 3, because the catalyst activity is not sufficiently maintained, and the growth of the carbon nanostructure cannot be sustained sufficiently. .

[0011] The present invention has been made in view of the above-described problems, and an object of the present invention is to maintain the growth of the carbon nanostructure and to produce a carbon nanostructure of high quality. The object of the present invention is to provide a manufacturing method of a product and a gas for manufacturing a carbon nanostructure used therefor.

[0012] In order to solve the above problems, a method for producing a carbon nanostructure according to the present invention includes at least a raw material gas containing carbon that is a raw material of the carbon nanostructure, and a carrier that conveys the raw material gas. In the method for producing a carbon nanostructure by supplying a gas to a reaction chamber in which a catalyst containing at least an iron element is disposed, a reducing gas for supplying hydrogen into the reaction chamber is further introduced into the reaction chamber. It is characterized in that an acidic gas having an acidic property with respect to carbon is supplied to the reaction chamber.

[0013] According to the above configuration, due to hydrogen derived from the reducing gas, the equilibrium of the decomposition reaction of the raw material gas moves in the direction opposite to the direction in which decomposition proceeds according to the principle of Le Chatelier. In other words, in the manufacturing process of the carbon nanostructure, the raw material gas is decomposed to generate a carbon and hydrogen decomposition reaction. The hydrogen derived from the reducing gas causes an equilibrium force decomposition of the decomposition reaction. It moves in the opposite direction to the direction in which. As a result, the rate of decomposition becomes slower. That is, the production rate of the carbon becomes slow. Therefore, it is possible to prevent the generation of excess carbon derived from the source gas, and it is possible to prevent the catalyst from being deactivated due to the excess carbon being deposited on the surface of the catalyst.

[0014] Accordingly, the growth of carbon nanostructures, particularly the carbon nanostructures in the second stage The growth of objects can be sustained, and high-quality carbon nanostructures can be produced. Furthermore, since the amount of source gas, which is a combustible gas such as ethylene, can be reduced, carbon nanostructures can be manufactured at low cost and safety is improved.

[0015] According to the above configuration, the carbon deposited on the catalyst surface can be oxidized, that is, combusted and removed. Therefore, the activity of the catalyst surface is maintained.

[0016] Accordingly, the growth of the carbon nanostructure, particularly the growth of the carbon nanostructure in the second stage can be maintained, and a higher quality carbon nanostructure can be produced.

In the method for producing a carbon nanostructure according to the present invention, in order to solve the above problems, at least two gases out of the source gas, the carrier gas, and the reducing gas are supplied to the reaction chamber. It is preferable to mix in advance before carrying out.

[0018] In the production of the carbon nanostructure, the ratio of the supply amounts of the raw material gas, the carrier gas, and the reducing gas affects the quality of the obtained carbon nanostructure. And according to said structure, before supplying to the said reaction chamber, in the gas mixed, at least 2 gas is mixed previously among the said source gas, the said carrier gas, and the said reducing gas. , The ratio of the supply amount can be easily adjusted.

[0019] Therefore, in addition to improving the sustainability of the growth of the carbon nanostructure by the reducing gas, it becomes easier to adjust the ratio of the supply amount of the supplied gas, thereby further improving the quality of the carbon nanostructure. Manufacture is possible.

[0020] In the method for producing a carbon nanostructure according to the present invention, in order to solve the above problems, the supply rate of the source gas (g / min) is set to the supply rate of the reducing gas (g / min). Divided power 0. 05-0.

[0021] According to the above configuration, since the equilibrium of the decomposition reaction moves in the direction opposite to the direction in which the decomposition proceeds, it is possible to prevent carbon derived from the source gas from being deposited on the surface of the catalyst. . On the other hand, since it does not move too much in the direction in which the decomposition proceeds, the carbon power derived from the raw material gas is supplied to the catalyst at a suitable rate and used for the synthesis of the carbon nanostructure.

[0022] Therefore, in particular, the growth of the carbon nanostructure in the second stage can be sustained. Can be performed more efficiently, and high-quality carbon nanostructures can be efficiently manufactured.

In the method for producing a carbon nanostructure according to the present invention, in order to solve the above problems, the supply amount of the oxidizing gas is 150 ppm to 500 ppm of the total amount of gas supplied to the reaction chamber. I prefer to be there!

[0024] According to the above configuration, the carbon deposited on the catalyst surface is removed. On the other hand, there is no need to remove carbon necessary for the production of strong single-bone nanostructures. Therefore, the carbon derived from the raw material gas is supplied to the catalyst at a suitable rate and used for the synthesis of the carbon nanostructure.

[0025] Therefore, it is possible to efficiently produce high-quality carbon nanostructures.

In the method for producing a carbon nanostructure according to the present invention, in order to solve the above problem, a value obtained by dividing the supply rate of the raw material gas by the amount of the catalyst is 100 to 100000 (lZmin

) Is preferable.

[0027] According to the above configuration, since the equilibrium of the decomposition reaction moves in the direction opposite to the direction in which the decomposition proceeds, it is possible to prevent carbon derived from the source gas from being deposited on the surface of the catalyst. . On the other hand, since it does not move too much in the direction in which the decomposition proceeds, the carbon power derived from the raw material gas is supplied to the catalyst at a suitable rate and used for the synthesis of the carbon nanostructure.

[0028] Therefore, in particular, the growth of the carbon nanostructure in the second stage can be sustained, and the carbon nanostructure can be more efficiently produced, and the high-quality carbon nanostructure can be efficiently produced. It becomes.

In the carbon nanostructure-producing gas according to the present invention, in order to solve the above problems, at least a raw material gas containing carbon that is a raw material of the carbon nanostructure, or a carrier gas that conveys the raw material gas And a reducing gas that supplies hydrogen into the reaction chamber, and the mixture further includes an acidic gas.

[0030] According to the above configuration, by producing the carbon nanostructure using the carbon nanostructure production gas, the equilibrium of the decomposition reaction of the raw material gas by hydrogen derived from the reducing gas is achieved. However, it moves in the direction opposite to the direction in which the decomposition proceeds due to the principle of Le Chatelier. Therefore, the speed of decomposition becomes slow. Therefore, excess from the source gas Generation of excess carbon can be prevented, and deactivation of the catalyst due to deposition of the excess carbon on the surface of the catalyst can be prevented.

[0031] Accordingly, the growth of the carbon nanostructure in the second stage can be continued, and a high-quality carbon nanostructure can be produced.

[0032] Further, according to the above-described configuration, carbon deposited on the catalyst surface is oxidized, that is, burned and removed by manufacturing the carbon nanostructure using the carbon nanostructure manufacturing gas. It becomes possible to do. Therefore, the activity of the catalyst surface is maintained.

[0033] Therefore, the growth of the carbon nanostructure, particularly the growth of the carbon nanostructure in the second stage can be sustained, and a higher quality carbon nanostructure can be produced.

[0034] In the gas for producing carbon nanostructures according to the present invention, in order to solve the above problems, the raw material gas and the reducing gas are mixed in a weight ratio of 0.05: 1 to 0.6: 1. It is preferable to include a mixed mixture.

[0035] According to the above configuration, by producing the carbon nanostructure using the carbon nanostructure production gas, the equilibrium of the decomposition reaction moves in the direction opposite to the direction in which the decomposition proceeds. Therefore, it is possible to prevent the carbon derived from the raw material gas from being deposited on the surface of the catalyst. On the other hand, since it does not move too much in the direction in which the decomposition proceeds, the carbon power derived from the raw material gas is supplied to the catalyst at a suitable rate and used for synthesis of the carbon nanostructure.

[0036] Therefore, in particular, the growth of the carbon nanostructures in the second stage can be sustained, and the carbon nanostructures can be efficiently produced, and high-quality carbon nanostructures can be efficiently produced. It becomes.

In the gas for producing carbon nanostructures according to the present invention, in order to solve the above problems, the raw material gas and the reducing gas are mixed at a weight ratio of 0.05: 1 to 0.6: 1. In addition, it is preferable to include a mixture in which the acidic gas is mixed with the reducing gas at a concentration of 375 ppm to 1250 ppm.

[0038] According to the above configuration, the carbon deposited on the catalyst surface is removed by manufacturing the carbon nanostructure using the carbon nanostructure manufacturing gas. On the other hand, it does not remove the carbon necessary for the production of carbon nanostructures. Therefore, the raw material gas Carbon derived from carbon is supplied to the catalyst at a suitable rate and used for the synthesis of carbon nanostructures.

[0039] Therefore, it is possible to efficiently produce high-quality carbon nanostructures.

[0040] In the gas for producing carbon nanostructures according to the present invention, in order to solve the above problems, at least selected from the group consisting of the above raw material gas power acetylene, ethylene and methane power

It is preferable to be a kind of gas.

[0041] According to the above configuration, the source gas does not generate an extra substance other than carbon and hydrogen, which are constituent elements of the carbon nanostructure. In addition, it is inexpensive and easily available, and is highly reactive with the above catalyst.

[0042] Therefore, it is possible to produce a high-quality carbon nanostructure.

[0043] In the gas for producing a carbon nanostructure according to the present invention, in order to solve the above-mentioned problem, the reducing gas is selected from a group power consisting of hydrogen, ammonia and hydrogen sulfide. Gas is preferred!

[0044] According to the above-described configuration, the reducing gas can be used to produce the carbon nanostructure as a component other than hydrogen necessary for moving the equilibrium of the decomposition reaction in the direction in which the decomposition proceeds. Don't produce extra substances that hinder!

[0045] Therefore, it is possible to produce a higher quality carbon nanostructure.

[0046] In the gas for producing carbon nanostructures according to the present invention, in order to solve the above problems, the oxidizing gas power water, oxygen, acetone, alcohol, dimethylformamide, CO, C

2

The group force of 0, O and H 2 O forces is preferably at least one gas selected.

3 2 2

[0047] According to the above configuration, carbon deposited on the catalyst surface can be efficiently removed by manufacturing the carbon nanostructure using the carbon nanostructure manufacturing gas. Monkey.

[0048] Therefore, a higher quality carbon nanostructure can be efficiently produced.

[0049] Other objects, features, and advantages of the present invention will be fully understood from the following description. The advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

Brief Description of Drawings [0050] FIG. 1 is a schematic configuration diagram of a carbon nanostructure manufacturing apparatus in the present embodiment.

FIG. 2 is a diagram schematically showing oxidation and micronization of a catalyst on a catalyst substrate in the present embodiment.

FIG. 3 is a diagram showing the results of examining the ratio of the supply amount of reducing gas to the supply amount of raw material gas in this example.

FIG. 4 is a graph showing the results of examining the ratio of the supply amount of the acidic gas to the supply amount of the raw material gas in this example.

[Fig. 5] In this example, the relationship between the holding time after the temperature raising step and the height of the obtained carbon nanotube was examined.

FIG. 6 is a diagram showing the results of observing the appearance of carbon nanotubes obtained in this example.

FIG. 7 is a diagram showing the results of observing the carbon nanotubes obtained in this example with a transmission microscope.

Explanation of symbols

[0051] 2 Carbon nanostructure

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention is described below with reference to FIGS. 1 and 2.

In the present embodiment, a raw material gas, a carrier gas, and a reducing gas, which will be described later, are supplied to a reaction chamber in which carbon nanostructures are grown using a carbon nanostructure manufacturing apparatus exemplified below. By doing so, the carbon nanostructure is manufactured. However, the scope of the present invention is not limited by these explanations, and can be implemented with appropriate modifications within the scope of the present invention other than the following examples.

FIG. 1 is a schematic configuration diagram of a carbon nanostructure manufacturing apparatus according to an embodiment of the present invention. The manufacturing apparatus is a carbon nanostructure manufacturing apparatus that manufactures a carbon nanostructure using a CCVD method which is a form of the CVD method. The manufacturing apparatus includes a reaction chamber 4 in which a carbon nanostructure growth reaction is performed, and a reaction heater 1 for raising the temperature of the reaction chamber 4. The reaction chamber 4 has a carbon nanostructure growth reaction. A catalyst body 6 that catalyzes is disposed. Carbon nanostructures 2 grow on the surface of the catalyst body 6 by the CCVD method. That is, in this embodiment, the carbon nanostructure physical force carbon nanostructure 2 according to the present invention is illustrated.

[0055] Here, for the purposes of this specification, "carbon nanostructure" is a nano-sized substance that is composed of carbon nuclear power. For example, carbon nanotubes and beads with beads formed on carbon nanotubes are attached. These include carbon nanotubes, carbon nanobrushes with many carbon nanotubes, carbon nanotwists with twisted carbon nanotubes, and coiled carbon nanocoils. In this specification, these substances are collectively referred to as “carbon nanostructures”.

[0056] Further, in the present specification, the "CVD method" is a general term for a method in which a source gas is decomposed in a reaction vessel to grow a target substance, and the decomposition means includes heat, Various decomposition means such as electron beam, laser beam, and ion beam are included in the meaning.

[0057] A gas exhaust line 3 is communicated with one end of the reaction chamber 4, and a carrier gas container (not shown) is connected to the flow path connected to the gas exhaust line 3 via opening and closing valves 5 and 7. It is connected to the.

[0058] The carrier gas is not limited as long as it can transport a source gas to be described later and does not react with the source gas or a reducing gas to be described later. For example, inert gases such as helium (He), argon (Ar), neon, N, CO, krypton, xenon,

twenty two

The mixed gas is used. Of these, a mixed gas of helium and argon is preferable. The source gas is consumed by the reaction, whereas the carrier gas has no reaction and is not consumed.

[0059] The raw material gas according to the present embodiment is not limited as long as it includes carbon that is a raw material of the carbon nanostructure, and is not limited to organic gases such as hydrocarbons, sulfur-containing organic gases, and phosphorus-containing organic gases. If you use ヽ. Among organic gases, hydrocarbons that do not generate extra substances are preferred. In particular, ethylene H) is cheap and easily available, and carbon nanostructures

twenty four

Since it has a high reactivity with the catalyst used when producing a product, it can be suitably used as the raw material gas.

[0060] Examples of hydrocarbons include alkane compounds such as methane and ethane, ethylene, butadiene, and the like. Alkene compounds such as alkene compounds, alkyne compounds such as acetylene, aryl hydrocarbon compounds such as benzene, toluene and styrene, aromatic hydrocarbons having condensed rings such as indene, naphthalene and phenanthrene, cycloparaffin compounds such as cyclopropane and cyclohexane Products, cycloolefin compounds such as cyclopentene, and alicyclic hydrocarbon compounds having a condensed ring such as steroids can be used.

[0061] It is also possible to use a mixed hydrocarbon gas in which two or more of the above hydrocarbons are mixed. In particular, a mixed hydrocarbon gas obtained by mixing two or more gases among hydrocarbons, preferably low molecules such as acetylene, arylene, ethylene, benzene, toluene, and methane is preferable.

The source gas is supplied from the source gas container (not shown) to the reaction chamber 4 through the source gas inflow passage 9 provided at the other end of the reaction chamber 4. In the source gas container, the source gas is reduced in pressure to a predetermined pressure by a regulator (not shown). The above-mentioned source gas whose pressure has been reduced is adjusted to a predetermined flow rate by a source gas flow rate controller 8 having a mass flow controller (MFC) force. The raw material gas flow rate controller 8 is provided in the inflow passage communicating with the raw material gas inflow passage 9, and the raw material gas is supplied through the electromagnetic three-way valves 10, 12 and the opening / closing valve 11. The carrier gas is supplied with the carrier gas container force, and the carrier gas is supplied so as to merge with the raw material gas inflow passage 9 as will be described later through the two flow paths provided with the gas flow controllers 22 and 23. The

In the present embodiment, reducing gas is supplied to the reaction chamber 4. With the reducing gas, it is possible to prevent the catalyst from being deactivated, and to perform a slow growth process of the carbon nanostructure described later continuously and continuously. That is, since the slow growth process can be continued for a long time, a long and sized carbon nanostructure can be manufactured. For example, 5-7 mm carbon nanostructures can be manufactured.

[0064] The reducing gas is not limited as long as it is a gas capable of supplying hydrogen into the reaction chamber 4, but hydrogen, ammonia, and hydrogen sulfide are preferable. These may be used alone or as a mixture of two or more. A more preferred reducing gas is hydrogen. Hydrogen does not produce any extra material other than hydrogen necessary to move the equilibrium of the decomposition reaction in the direction in which the decomposition does not proceed. In other words, Most preferably, hydrogen is supplied directly to the reaction chamber 4. In the reaction chamber 4, hydrogen produced from ammonia hydrosulfide may be supplied depending on the reaction with the raw material gas, the temperature in the reaction chamber 4, the pressure condition, or the like.

[0065] The ratio of the feed rate of the source gas (g / min) to the feed rate of the reducing gas (g / min) is appropriately determined according to the size, generation rate, etc. of the target carbon nanostructure. Although it may be set, the weight ratio is preferably 0.05: 1 to 0.6: 1, and more preferably 0.1: 1 to 0.3: 1. Further, the value obtained by dividing the feed rate (g / min) of the raw material gas by the catalyst amount (g) is preferably 100 to 100,000 (lZmin). At this time, the slow growth process of the carbon nanostructure described later can be performed more continuously and continuously.

[0066] Alternatively, a gas (carbon nanostructure production gas) in which the reducing gas and the source gas are mixed in a weight ratio of 0.05: 1 to 0.6: 1 in advance may be used. Furthermore, it is preferable to use a carbon nanostructure-producing gas having a weight ratio of 0.1: 1 to 0.3: 1.

The reducing gas supply means is not limited as long as it is supplied to the reaction chamber 4.

That is, apart from other gases, only the reducing gas may be separately supplied to the reaction chamber 4 or may be supplied in advance mixed with other gases such as the above-mentioned source gas or the above carrier gas. . However, it is mixed with gas that may cause explosion by reacting with the reducing gas, such as O.

2

When handling, it is natural to be careful in handling so that there is no risk of explosion. Preferably, a gas (carbon nanostructure production gas) in which the reducing gas is mixed with at least one of the carrier gas and the raw material gas is supplied to the reaction chamber 4. That is, it is preferable that the carbon nanostructure manufacturing gas is manufactured before being supplied to the reaction chamber 4.

[0068] The carbon nanostructure production gas is not limited to being produced in any of the steps of the production apparatus, and a container previously filled with a carrier gas or a raw material gas is filled with the carrier gas described above. It may be used as a container or a source gas container. Thus, as long as the reducing gas is finally supplied to the reaction chamber 4, any means can be used.

[0069] In the present embodiment, an acidic gas is used. The acidic gas is not limited as long as it is a gas having an oxidizing property with respect to carbon, but water, oxygen, acetone, alcohol, Dimethylformamide, CO, CO, O and HO are preferred, more preferably water, oxygen

2 3 2 2

It is. These may be used alone or as a mixture of two or more. By using an oxidizing gas, carbon (amorphous carbon) deposited on the catalyst surface, which will be described later, can be oxidized, that is, burned and removed. Therefore, carbon nanostructures can be generated more continuously.

[0070] The mixing amount of the oxidizing gas may be appropriately set according to the size, generation rate, and the like of the target carbon nanostructure. Of the total amount of gas supplied to the reaction chamber, 150 ppm A force of ˜500 ppm S is preferable, more preferably 300 to 400 ppm. In addition, when mixing water and oxygen, it is not restricted to said range, It is preferable to mix water in the range of 0.05 ppm-3%, and oxygen at 0.01 ppb-l%. In addition, a gas (carbon nanostructure production gas) obtained by mixing the above-described reducing gas and the above-described raw material gas with the above-described acidic gas may be used in advance. The amount of the oxidizing gas mixed at this time may be appropriately set according to the amount of the raw material gas used. For example, when it is 40% of the total amount of gas used in the reducing gas power, the reducing gas may be mixed so as to be 375 ppm to 1250 ppm, more preferably 750 to 1000 ppm.

[0071] In the present embodiment, the oxygen-containing gas is supplied from an oxygen cylinder (not shown) filled to a predetermined concentration by a gravimetric method to a predetermined flow rate by an oxygen flow controller 13 in which oxygen also has an MFC force. Adjusted. The oxygen flow rate controller 13 is provided in the inflow path communicating with the raw material gas inflow path 9, and oxygen is supplied to the reaction chamber 4 through the electromagnetic three-way valve 14 and the opening / closing valve 11. An oxygen analyzer 21 is provided in the carrier gas introduction path 11 before the open / close valve 11, and oxygen from the oxygen cylinder is also introduced into the oxygen analyzer 21, and oxygen of an appropriate concentration is supplied to the reaction chamber 4. Monitor and ensure that is supplied.

The water adding device 15 is a water container provided with a heater. The purified carrier gas is introduced into the warmed water of the moisture adding device 15 via the gas flow controller 16, and the moisture added by the flow mixing method and the mixed gas of the carrier gas are electromagnetically mixed. It is supplied to the reaction chamber 4 through the valve 18 and the open / close valve 11. The carrier gas is also merged and mixed via the gas flow controller 20 at the outlet side of the moisture addition device 15. Mixing moisture and carrier gas A moisture analyzer 17 is provided in the monitoring bypass 19 provided in the gas introduction channel, and monitoring is performed so that the moisture analyzer 17 supplies water with an appropriate concentration to the reaction chamber 4.

[0073] The catalyst body 6 is a substrate on which a carbon nanostructure growth reaction catalyst is formed on the surface by film formation or the like. The shape of the substrate is a substrate, a multilayer substrate, a cylinder, a polyhedron, a pellet, a powder, (Hereinafter, in the present embodiment, the substrate on which the catalyst is formed is referred to as a “catalyst substrate”.) O

[0074] The catalyst to be used is not limited as long as it contains an iron element, but iron oxide is more preferable, and triiron tetroxide is more preferable. Magnetite as a component is preferable. Further, a catalyst comprising iron element, that is, pure iron is used to supply an oxidizing gas to the carbon nanostructure device to oxidize the pure iron, thereby converting the pure iron into magnetite. Let me do it. Even when a V-shifted catalyst is used, it is preferable that the catalyst be finely atomized in the temperature raising step described later.

That is, in the carbon nanostructure manufacturing apparatus according to this embodiment, the catalyst body 6 containing iron element is arranged in advance in the reaction chamber 4, and the raw material gas is supplied and circulated through the reaction chamber 4. Before the gas is supplied and circulated into the reaction chamber 4, a mechanism may be provided in which an acidic gas is supplied to the reaction chamber 4 together with the carrier gas to convert the catalyst body 6 into magnetite. Further, in the process of growing the carbon nanostructure by the catalyst body 6, the raw material gas and the oxidizing gas may be circulated into the reaction chamber 4.

[0076] The method for forming the iron catalyst on the catalyst substrate is not limited to any means such as Ar sputtering, electron beam evaporation, dip coating, or spin coating, but it is uniformly in the nanometer order. It is important that a catalyst film having a thickness can be formed. The powder is dispersed in a liquid in the order of nanometers and uniformly dispersed in the liquid phase. There is no particular limitation as long as the catalyst particles of the order are formed.

[0077] The substrate used for the catalyst substrate is preferably a material that does not form a compound with iron as a catalyst at the reaction temperature for synthesizing the carbon nanostructure. For example, reaction temperature From the viewpoints of stability, surface smoothness, cost, and reuse, silicon substrates or, in particular, silicon oxide with a sufficiently oxidized surface of silicon substrate S1 as shown in (2A) of FIG. It is preferable to use a silicon substrate provided with a layer S2. When the catalyst generates a compound with the catalyst substrate or has a strong affinity with the catalyst substrate, the catalyst is oxidized into particles in the heating step described later. This does not occur well, and the carbon nanostructure formation probability may be reduced.

Next, the gas flow path switching mechanism will be described. The electromagnetic three-way valve 10 is controlled to a cut-off state and a supply state by the action of an automatic valve controller (not shown). That is, in the state in which the source gas is shut off, the source gas is exhausted to the exhaust side, and in the source gas supply state, the source gas is supplied to the injection side, and the source gas is separated from the carrier gas at the junction where the on-off valve 11 is reached. Mixed

[0079] When the electromagnetic three-way valve 10 is used, since the source gas is already controlled to a predetermined flow rate, there is no initial fluctuation of the source gas even if it is switched to the injection side. In addition, since the switching is performed by electromagnetic action, the switching is performed instantaneously without any pressure fluctuation, and the raw material gas is supplied at a predetermined flow rate without any slow rise of the raw material gas. Even when the source gas is switched to a state where the supply state force is shut off, the flow rate of the source gas can be instantaneously switched to zero without pressure fluctuations by electromagnetic action by the automatic valve controller, and there is no slow fall of the source gas. .

[0080] As described above, if the electromagnetic three-way valve 10 is used, the supply and cut-off of the raw material gas to the reaction chamber 4 can be instantaneously performed, and the flow rate does not fluctuate at all in the changing process. Therefore, if the total flow rate is constant, the gas pressure inside the reaction chamber 4 is constant. Since the source gas is decomposed while this total pressure (gas pressure) is constant, pressure fluctuation does not occur inside the reaction chamber 4, the gas conditions of the catalyst body 8 can be made constant, and the carbon nanostructure 2 It has the effect of promoting growth.

[0081] The carrier gas and the source gas are mixed at the junction, and then supplied to the reaction chamber 4 from a gas supply nozzle (not shown) provided at the tip of the source gas inflow passage 9 as a mixed flow. The reaction chamber 4 is heated to a temperature range where carbon nanostructures are most easily generated, and the raw material gas is thermally decomposed in the vicinity of the catalyst body 6, and carbon nanostructures 2 are formed from the decomposition products on the surface of the catalyst body 6. To be long.

[0082] In the present embodiment, a force that uses the thermal decomposition method to decompose the source gas over the CVD method, such as a laser beam decomposition method, an electron beam decomposition method, an ion beam decomposition method, a plasma decomposition method, Other decomposition methods can be used. In any case, the carbon nanostructure 2 is formed on the surface of the catalyst body 6 from these decomposition products. On the surface of the catalyst body 6, a part of the raw material gas is converted into carbon nanostructures, and the unreacted raw material gas that has not contributed to the reaction is discharged from the gas discharge line 3 together with the carrier gas.

[0083] <Temperature raising process>

In the temperature raising step, the temperature in the reaction chamber 4 is raised to the reaction temperature before starting the growth reaction of the carbon nanostructure. The reaction temperature may be appropriately set depending on the size of the target carbon nanostructure, the raw material gas used, the carrier gas, the reducing gas, etc., but is preferably 600 ° C 1200 ° C force S, more preferably 700 ° C 900 ° C.

[0084] In the temperature raising step, as shown in FIG. 2 (2A), in the catalyst layer S3 on the silicon oxide layer S2 of the substrate on which the catalyst is formed, the catalyst is oxidized and atomized at the time of temperature rise. Occur at the same time. FIG. 2 is a diagram schematically showing oxidation and fine particle formation of the catalyst on the catalyst substrate.

[0085] Then, as shown in FIG. 2 (2A), the catalyst that has undergone moderate oxidation combines fine polycrystalline particles A of the order of 1 or less in the film formation step, and is several nanometers to several nanometers. Forms large particles BC on the order of 10 nm. This is the so-called micronization process. Furthermore, it is preferable that the fine particles are formed near the surface to form oxides.

[0086] <Rapid growth process after starting raw material supply>

When the supply of ethylene gas, which is a raw material gas, is started, the synthesis reaction of carbon nanostructures is based on a two-step reaction: initial “rapid growth” and “slow growth” that grows while producing amorphous carbon. It has been found that there is growth.

[0087] In the following, the force for explaining the case where the source gas is ethylene is the same mechanism for other source gases.

[0088] The above "rapid growth" in the initial stage is a reaction whose rate is determined by the reaction itself mainly composed of the following formulas (1) and (2) on the catalyst surface.

2Fe O + 2C H → 4FeC + 4H O + O (!) 2Fe O + 2C H → 2FeO + 4FeC + 4H O + O (2)

3 4 2 4 2 2…

This initial rapid growth is due to a moderate affinity between the catalyst and the catalyst substrate in the catalyst, a moderate oxidation of fine particles in the heating process, a sufficient amount of source gas relative to the catalyst amount, and introduction of a source gas. In view of the fluctuation suppression conditions, the formation of carbon nanostructures with a length of 50 μm to 100 μm can be achieved. However, in the conventional technology, after the “rapid growth” is stopped by the oxygen amount held by the catalyst being consumed by the reaction, as described later, due to the excess amorphous carbon supplied with the raw material gas power. By covering the surface of the catalyst, it becomes difficult to contact the catalyst and the raw material gas, and eventually the reaction is stopped.

[0089] When the oxygen retained by the catalyst is approximately the same, the length of the carbon nanostructure is approximately the same, so that there is reproducibility and at the same time the force depends on the amount of oxygen retained in the initial catalyst. It can be understood that the length of one-bon nanostructure is determined.

[0090] <Slow growth process of carbon nanostructure>

Next, we will explain the second stage of growth, or “slow growth,” that proceeds while producing amorphous carbon, which is indispensable for manufacturing carbon nanostructures.

[0091] (2B) of FIG. 2 is a diagram schematically illustrating the growth of carbon nanostructures. In Fig. 2 (2B), D is a catalyst particle containing the above iron element (catalyst particle), and F is a multilayer layer of carbon nanostructures that grow. E is a region on the catalyst particle D where the catalyst particle D and the source gas are in contact with each other.

[0092] As shown in FIG. 2 (2B), the catalyst particles D in contact with ethylene have carbon nanostructures on the surface of the carbide (FeC) of the catalyst particles D carbonized by the ethylene-derived carbon. The multilayer layer F constituting the wall is formed. Then, the amorphous carbon produced by the reaction between the catalyst particles D and the raw material gas pushes out the multilayer layer F, thereby forming a powerful nano structure. Note that the arrows shown in FIG. 2 (2B) indicate the direction of carbon diffusion.

[0093] When the affinity between the catalyst particle D and the catalyst substrate is strong, the catalyst particle D is not spherical, and the multilayer layers F on both sides are not extruded at a uniform speed and are not oriented vertically. It becomes. Also, if there is no affinity between the catalyst substrate and the catalyst particles D, the multilayer The carrier F moves toward the substrate while the catalyst particle D exists at the tip of the carbon nanostructure, and the carbon nanostructure grows. In the case of moderate affinity, the multi-layer layer F stretches vertically to some extent, and the catalyst may float against the force pushed out by the diffusion of carbon, and may exist at the midpoint of the length of the carbon nanostructure. .

[0094] Here, for slow growth!

2FeO + C H → 2FeC + 2H O (3)

2 4 2…

And formula (4)

Fe + C H → FeC + C + 2H

twenty four)

twenty four

It can be understood that this reaction is rate-limiting by the surface diffusion of carbon.

Furthermore, C H in the above formulas (3) and (4) is the following formula (5)

twenty four

C H → 2C + + 2H…)

2 4 2

It is thought that thermal decomposition indicated by That is, it is considered that the raw material gas is decomposed in the process of manufacturing the carbon nanostructure to generate radical carbon (C +) and hydrogen.

[0096] Then, at the reaction point (region の) where the catalyst particle D and the source gas are in contact with each other, the radical carbon (C +) in the above formula (5) is converted into a multilayered layer composed of the amorphous carbon. When supplied at a rate higher than the diffusion rate for extruding F, excessively generated amorphous carbon accumulates on the surface of the catalyst, thereby preventing contact between the catalyst and the source gas. Continuous growth in "Sustainable growth" stops.

However, according to the present embodiment, the reducing gas is supplied to the reaction chamber 4. And since there is a large amount of soot derived from the reducing gas, the above formula (5)

2

Η will increase, and according to Le Châtelier's principle,

2

The rate of thermal decomposition of tyrene is reduced. As a result, excessive generation of the amorphous carbon can be prevented. That is, the reducing gas functions as a suppression component for the amorphous carbon. Therefore, the deposition on the catalyst surface by the amorphous carbon can be prevented very efficiently, and the deactivation of the catalyst can be prevented. As a result, continuous carbon nanostructure growth can be achieved. That is, the “reducing gas” in this specification means the equilibrium of thermal decomposition of the source gas. It can be said that the gas moves in a direction to suppress the solution. It can also be said that the material gas has the property of giving hydrogen to radical carbon generated by thermal decomposition.

Example 1

[0098] Examples of producing carbon nanotubes using the production method and production gas of carbon nanostructures according to the present invention are shown below.

[0099] In this example, by changing the supply amount of the source gas, the ratio of the supply amounts of the carrier gas, the source gas, the reducing gas, and the acidic gas, which will be described later, is changed. The results of manufacturing were compared.

[0100] The carbon nanostructure manufacturing apparatus according to Fig. 1 described in the above embodiment was used as the manufacturing apparatus. He (purity 99.9999%) was used as a carrier gas. He contained 50 ppb of oxygen as a minor component.

[0101] H 2 O is used as the oxidizing gas, and the H 2 O is used for the entire gas supplied to the reaction chamber.

twenty two

Mixed to contain 350ppm of the amount

Further, H (purity 99.9999%) was mixed with the carrier gas as a reducing gas.

2

[0102] Ethylene was used as the source gas.

[0103] The total amount of gas supplied to the reaction chamber of the carbon nanostructure manufacturing apparatus was 20 CKcm / min at 1 atm.

It should be noted that the numerical values relating to the gas supply rate (unit: cm ³ / min) shown in this example and the following examples are all values at 1 atm and 25 ° C.

[0105] The reaction chamber was heated to 750 ° C in this example and in all the following examples.

(Hereinafter referred to as “heating step”.) O

[0106] Until the above reaction chamber is heated to 750 ° C, He (carrier gas) is supplied at 120 (cmVmin), and (reducing gas) is supplied at 80 (cm ³ / min). Supply He after being heated to

2

A part of was replaced with ethylene gas. In other words, in this example, the total gas supply amount was set to 200 (cm ³ / min) at 1 atmospheric pressure, and after heating, a part of He was replaced with ethylene, thereby supplying each gas supply amount. The ratio of was changed. The amount of ethylene supplied, that is, the amount of He replaced after the temperature raising step, is in the range of 5% to 25% of 200 (cmVmin), which is the total amount of gas supplied. is there.

[0107] As shown in FIG. 1, there are two carrier gas supply paths.

[0108] Fe was used as the catalyst. The Fe catalyst is a lcm x 1cm square, and a thin film with a thickness of lnm.

2

Installed through O.

Three

[0109] The ratio of the supply amount of reducing gas (H) to the supply amount of raw material gas (ethylene) was examined.

2

The results are shown in Figure 3. The horizontal axis is the amount of ethylene supplied divided by the amount of H. Vertical

2

The axis is the height of the carbon nanotube obtained by holding for 30 minutes after the temperature raising step.

[0110] As shown in FIG. 3, when the supply capacity of ethylene is 200% (cm ³ / min) above, 7.5%, that is, the weight ratio between the amount of ethylene supplied and the amount of H is 0. 1875: When 1

2

The height force of the obtained carbon nanotube was the largest value.

Example 2

[0111] Examples of producing carbon nanotubes using the production method and production gas of carbon nanostructures according to the present invention are shown below.

[0112] In this example, by changing the supply amount of the acidic gas, the ratio of the supply amounts of the carrier gas, the raw material gas, the reducing gas, and the acidic gas is changed, thereby The results of manufacturing the structure were compared.

[0113] The same carrier gas, raw material gas, reducing gas, acidic gas and catalyst as in Example 1 were used.

[0114] The temperature raising step was also performed in the same manner as in Example 1. After the reaction chamber was heated to 750 ° C, the total gas supply rate was set to 200 (cmVmin), and after heating, 7. 5% (15 (cm ³ / min)) was replaced with ethylene.

[0115] The acidic gas uses H 2 O and has a concentration with respect to the total amount of gas supplied to the reaction chamber.

2

150ρρπ! In the range of ~ 500ppm, it was changed in increments of 50ppm.

[0116] The ratio of the supply amount of oxidizing gas (H 2 O) to the supply amount of raw material gas (ethylene) was examined.

2

The results are shown in Fig. 4. The horizontal axis is the value obtained by dividing the amount of ethylene supplied by the amount of H 2 O.

2

The vertical axis shows the height of the obtained carbon nanotubes by holding for 30 minutes after the temperature raising step. That's it.

[0117] As shown in FIG. 4, when the supply capacity of H 2 O is 350 ppm,

2

The height of Yub was the largest value.

Example 3

[0118] Next, the relationship between the holding time after the heating step and the height of the obtained carbon nanotubes was examined.

B, J.

[0119] In this example, the supply amount of the raw material gas (ethylene) was set to 7.5% (15 (cmVmin)) with respect to 200 (cmVmin), which is the total amount of gas to be supplied. And so on.

[0120] The retention time was varied between 10 minutes and 12 hours. The same procedure as in Example 1 was performed except for the ratio of gas supply and the holding time. The results are shown in FIG.

[0121] As shown in FIG. 5, it was confirmed that the height of the carbon nanotubes increased even after 12 hours had elapsed after the temperature increase. In other words, the activity of the catalyst was maintained even after 12 hours. Further, in this example, the carbon nanotubes obtained 12 hours after the temperature raising step had a length of 7 mm (hereinafter referred to as “7 mm carbon nanotube” for the sake of simplicity). This is an unreported length so far.

[0122] Fig. 6 shows the result of observing the appearance of the 7 mm carbon nanotube.

[0123] Fig. 6 (a) is a diagram showing the appearance of a group of 7 mm carbon nanotubes. From FIG. 6 (a), it can be seen that the carbon nanotube has a height of 7 mm.

[0124] (b) to (f) of FIG. 6 are diagrams showing the results of observing the appearance of the 7 mm carbon nanotube by SEM. FIG. 6B is a view of the carbon nanotube group shown in FIG. 6A observed from above (from a plane perpendicular to the length direction of the carbon nanotube) by SEM. This reveals that the surface of the surface perpendicular to the length direction of the carbon nanotube group is smooth and flat. This indicates that the individual 7 mm carbon nanotubes have grown to an equal length.

[0125] FIGS. 6 (c) and 6 (e) are views of the upper part (front end side) and the lower part of the 7 mm carbon nanotube observed by SEM, respectively. As a result, it can be seen that the 7 mm carbon nanotubes are dense and aligned vertically.

[0126] Fig. 6 (d) and Fig. 6 (f) show the upper part (tip side) of the 7mm carbon nanotube. ) Are enlarged views of the lower part. This shows that the 7mm carbon nanotubes are curved at the nanoscale and entangled with each other.

Next, FIG. 7 shows the result of observation of the 7 mm carbon nanotubes with a transmission electron microscope.

From (a) and (b) of FIG. 7, it was confirmed that the 7-mm carbon nanotubes did not contain metal nanoparticles derived from the catalyst. Most of the above 7mm carbon nanotubes were also shown to have a double wall structure.

Note that the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims, and the technical means disclosed in the different embodiments are appropriately combined. Embodiments obtained in this manner are also included in the technical scope of the present invention. Example 4

[0130] Carbon nanostructures were obtained in the same manner as in Example 3 except that oxidizing gas (H 2 O) was not used.

2

The product was manufactured.

As a result, the length of the carbon nanotube obtained after 2 hours was 500 m.

In this way, when an acidic gas is not used, a certain degree of effect can be obtained, but as shown in Examples 1 to 3, by supplying both an acidic gas and a reducing gas, Furthermore, it was shown that an excellent effect is exhibited.

Comparative Example 1

[0132] The reducing gas (H) is not used and the supply amount of the carrier gas (He) is set to 200 (cmVmin)

2

Produced carbon nanostructures in the same manner as in Example 3.

[0133] As a result, the length of the carbon nanotubes obtained after 2 hours was 100 μm or less.

[0134] As described above, the method for producing a carbon nanostructure according to the present invention includes a reaction chamber for producing a carbon nanostructure by using the reducing gas in addition to the raw material gas and the carrier gas. Therefore, the hydrogen derived from the reducing gas slows down the decomposition reaction of the raw material gas in the carbon nanostructure manufacturing process. Therefore, the deactivation of the catalyst due to the carbon derived from the source gas being deposited on the surface of the catalyst can be prevented. Furthermore, the method for producing a carbon nanostructure according to the present invention May supply an oxidizing gas having an oxidizing property to carbon to the reaction chamber. In this case, the carbon deposited on the catalyst surface can be removed by oxidation.

[0135] Therefore, the growth of carbon nanostructures, particularly the growth of carbon nanostructures in the second stage described above, can be sustained, and it becomes possible to produce high-quality carbon nanostructures. Play.

[0136] In addition, as described above, the gas for producing carbon nanostructures according to the present invention includes the above-mentioned raw material gas or a mixture of the carrier gas and the reducing gas. .

[0137] According to the above configuration, by producing the carbon nanostructure using the carbon nanostructure production gas, the decomposition reaction of the raw material gas is moderated by hydrogen derived from the reducing gas. To. Therefore, the deactivation of the catalyst due to the carbon derived from the source gas being deposited on the surface of the catalyst can be prevented. Furthermore, the carbon nanostructure manufacturing gas according to the present invention may include an oxidizing gas having an oxidizing property with respect to carbon. In this case, by using the carbon nanostructure manufacturing gas, the carbon deposited on the catalyst surface can be removed by oxidizing.

[0138] Therefore, the growth of carbon nanostructures, particularly the growth of carbon nanostructures in the second stage described above, can be sustained, and it becomes possible to produce high-quality carbon nanostructures. Play.

[0139] The specific embodiments or examples made in the detailed description section of the invention are to clarify the technical contents of the present invention, and are limited to such specific examples. Therefore, the present invention should not be construed in a narrow sense, and can be carried out with modifications within the spirit of the present invention and the scope of the claims described below.

Industrial applicability

[0140] According to the present invention, by appropriately setting the supply amount of a reducing gas such as hydrogen, which is a trace component in the carrier gas, with respect to the catalyst amount, high-quality carbon nanostructures with high density and high efficiency can be obtained. It is possible to realize a method for manufacturing a carbon nanostructure that enables manufacturing of a product.

Claims

The scope of the claims

[1] By supplying a source gas containing at least carbon as a raw material of the carbon nanostructure and a carrier gas carrying the source gas to a reaction chamber in which a catalyst containing at least an iron element is disposed, In a method of manufacturing a structure,

Furthermore, a reducing gas for supplying hydrogen into the reaction chamber is supplied to the reaction chamber, and an oxidizing gas having an oxidizing property with respect to carbon is supplied to the reaction chamber. Manufacturing method.

[2] At least two of the source gas, the carrier gas, and the reducing gas are used.

The method for producing a carbon nanostructure according to claim 1, wherein the carbon nanostructure is mixed in advance before being supplied to the reaction chamber.

[3] The value obtained by dividing the supply rate (g / min) of the source gas by the supply rate (g / min) of the reducing gas is 0.05 to 0.6. The method for producing a carbon nanostructure according to item 1 or 2 of the above item.

[4] The supply amount of the oxidizing gas is 150 ppm of the total amount of gas supplied to the reaction chamber.

The method for producing a carbon nanostructure according to any one of claims 1 to 3, wherein the carbon nanostructure is -500 ppm.

[5] The carbon according to claim 3 or 4, wherein a value obtained by dividing the supply rate of the raw material gas by the amount of the catalyst is 100 to: LOOOOO (lZmin) A method for producing a nanostructure.

[6] A mixture of a source gas containing at least carbon that is a raw material of the carbon nanostructure, or a carrier gas that conveys the source gas and a reducing gas that supplies hydrogen into the reaction chamber, and the mixture However, the gas for producing carbon nanostructures is characterized in that it contains sardine and acidic gas.

[7] The carbon according to claim 6, comprising a mixture in which the raw material gas and the reducing gas are mixed at a weight ratio of 0.05: 1 to 0.6: 1. Gas for manufacturing nanostructures.

[8] The raw material gas and the reducing gas are mixed at a weight ratio of 0.05: 1 to 0.6: 1,

Furthermore, the above acidic gas is mixed with the reducing gas at a concentration of 375 ppm to 1250 ppm. The carbon nanostructure-producing gas according to claim 6 or 7, wherein the gas for producing carbon nanostructure according to claim 6 is contained.

[9] Raw material gas power At least selected from the group consisting of acetylene, ethylene and methane power

The gas for producing carbon nanostructures according to any one of claims 6 to 8, wherein the gas is one kind of gas.

10. The reducing gas according to any one of claims 6 to 9, wherein the reducing gas is at least one gas selected from the group force consisting of hydrogen, ammonia, and hydrogen sulfide power 1 The carbon nanostructure manufacturing gas described in the paragraph.

[11] Above oxidizing gas power Water, oxygen, acetone, alcohol, dimethylformamide, CO,

2

CO, O, and H 2 O forces are also group forces.

3 2 2

The gas for producing carbon nanostructures according to any one of claims 6 to 10.