JPH09188509A - Production of monolayer carbon manotube - Google Patents

Production of monolayer carbon manotube

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Publication number
JPH09188509A
JPH09188509A JP8003636A JP363696A JPH09188509A JP H09188509 A JPH09188509 A JP H09188509A JP 8003636 A JP8003636 A JP 8003636A JP 363696 A JP363696 A JP 363696A JP H09188509 A JPH09188509 A JP H09188509A
Authority
JP
Japan
Prior art keywords
carbon
plasma
walled
nanotubes
graphite
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP8003636A
Other languages
Japanese (ja)
Other versions
JP2737736B2 (en
Inventor
Hideki Yoshikawa
英樹 吉川
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
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Filing date
Publication date
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Priority to JP8003636A priority Critical patent/JP2737736B2/en
Publication of JPH09188509A publication Critical patent/JPH09188509A/en
Application granted granted Critical
Publication of JP2737736B2 publication Critical patent/JP2737736B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Abstract

PROBLEM TO BE SOLVED: To provide a method for producing monolayer carbon nanotube, enabling its continuous production over a long time. SOLUTION: The objective monolayer carbon nanotube can be synthesized stably over a long time by using electrodeless high-frequency plasma without, in principle, any variation in plasma situation due to electrode exhaustion as observed in arc discharge process. Besides, formation of amorphous carbon and/or graphite as impurities can be suppressed without decreasing the yield of the aimed carbon nanotube by feeding the peripheral area of the high-frequency plasma with hydrogen gas to etch carbon and/or argon gas to rapidly drop gas temperature independently of raw material feed.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【発明の属する技術分野】本発明は、カーボン単層ナノ
チューブの製造方法に関し、特に長時間の連続製造が可
能なカーボン単層ナノチューブの製造方法に関する。
The present invention relates to a method for producing carbon single-walled nanotubes, and more particularly, to a method for producing carbon single-walled nanotubes capable of continuous production for a long time.

【0002】[0002]

【従来の技術】カーボンナノチューブは、厚さ数原子層
のグラファイト状炭素原子面を丸めた円筒が1個あるい
は数個入れ子になったものであり、外径がnmオーダー
の極めて微小な物質である。
2. Description of the Related Art A carbon nanotube is a cylinder in which one or several cylinders having rounded graphite-like carbon atomic planes of several atomic layers in thickness are nested, and are extremely minute substances with an outer diameter on the order of nm. .

【0003】数個以上の円筒状黒鉛層が同心円状に形成
された通常のカーボンナノチューブは、カーボンナノチ
ューブの電気特性や化学特性に大きなばらつきがあっ
た。そこで、チューブの形状が単層に制御されたカーボ
ン単層ナノチューブが開発された。
A typical carbon nanotube in which several or more cylindrical graphite layers are formed concentrically has a large variation in the electrical and chemical properties of the carbon nanotube. Therefore, a carbon single-walled nanotube in which the shape of the tube is controlled to a single-walled type has been developed.

【0004】カーボン単層ナノチューブの製法としては
従来、電極に炭素棒を使ったアーク放電が用いられてき
た。この手法では電極の炭素材を原料としてカーボンナ
ノチューブを合成するため、製造時間の経過と共に電極
が消費するのは避けられず、アーク放電の状態自身も経
時変化してしまう。
Conventionally, as a method for producing single-walled carbon nanotubes, arc discharge using a carbon rod as an electrode has been used. In this method, since carbon nanotubes are synthesized using the carbon material of the electrode as a raw material, it is inevitable that the electrode is consumed as the production time elapses, and the state of the arc discharge itself changes with time.

【0005】また、カーボン単層ナノチューブを高効率
に合成するには、原料の炭素以外に鉄、ニッケル等の金
属触媒を必要とする。アーク放電法では、これらの触媒
金属はしばしば炭素電極内に埋め込んだ形で供給される
が、放電時に電極が高温になると、炭素に比べ蒸気圧が
高い触媒金属が優先的に蒸発するため炭素と触媒の供給
量の比率が経時変化してしまう。
In order to synthesize carbon single-walled nanotubes with high efficiency, a metal catalyst such as iron or nickel is required in addition to carbon as a raw material. In the arc discharge method, these catalyst metals are often supplied in a form embedded in the carbon electrode. The ratio of the supply amount of the catalyst changes over time.

【0006】以上の理由からアーク放電法では、数分間
を越える製造条件の定常性を望めず、長時間のカーボン
単層ナノチューブの合成が困難である。
For the above reasons, in the arc discharge method, it is not possible to expect the continuity of the production condition exceeding several minutes, and it is difficult to synthesize the carbon single-walled nanotube for a long time.

【0007】[0007]

【発明が解決しようとする課題】カーボン単層ナノチュ
ーブはその結晶性の良さから強靱な炭素繊維となるが、
従来のアーク放電装置では炭素棒電極が消費され、また
炭素と触媒の供給量の比率が経時変化するため数分間を
越える長時間の運転ができず、実用に供せるだけのカー
ボン単層ナノチューブの収量を得ることは困難であっ
た。
The carbon single-walled nanotube becomes a tough carbon fiber due to its good crystallinity.
In the conventional arc discharge device, the carbon rod electrode is consumed, and the ratio of the supply amount of carbon and the catalyst changes with time. It was difficult to obtain a yield.

【0008】従ってカーボン単層ナノチューブの工業上
の発展により、長時間運転が可能な合成法の確立が避け
得ない課題となっている。
[0008] Therefore, with the industrial development of carbon single-walled nanotubes, it has become an inevitable problem to establish a synthesis method capable of operating for a long time.

【0009】又、カーボン単層ナノチューブ合成時にア
モルファスカーボンやグラファイトも生成してしまうた
め、これら他相の生成を抑制し、良質のカーボン単層ナ
ノチューブを得る製造条件を得ることも課題となってい
た。
In addition, since amorphous carbon and graphite are also generated during the synthesis of carbon single-walled nanotubes, it has also been a problem to suppress the formation of these other phases and to obtain production conditions for obtaining high-quality carbon single-walled nanotubes. .

【0010】[0010]

【課題を解決するための手段】先の課題を解決するには
プラズマに直接触れる炭素電極を使わずに高温プラズマ
を発生させる必要があるため、本発明では高周波コイル
によって無電極プラズマを発生させている。
In order to solve the above problems, it is necessary to generate high-temperature plasma without using a carbon electrode that directly contacts the plasma. I have.

【0011】この方法は、ガス流制御でプラズマ形状を
安定化させることにより、如何なる壁面にもプラズマを
接触させないことが可能で、カーボン単層ナノチューブ
合成に用いることにより、合成時間の制限が解消され
た。
According to this method, it is possible to prevent the plasma from contacting any wall surface by stabilizing the plasma shape by controlling the gas flow, and the use of the method for the synthesis of carbon single-walled nanotubes eliminates the limitation of the synthesis time. Was.

【0012】なお炭素原料としては、供給量の制御性の
良いガスを用いることが好ましくメタン等の炭化水素を
用いることができる。
As the carbon raw material, it is preferable to use a gas having good controllability of the supply amount, and a hydrocarbon such as methane can be used.

【0013】金属触媒を、炭素源とは全く独立にプラズ
マに供給すれば、炭素と金属触媒の供給量の比率が経時
変化することがない。
If the metal catalyst is supplied to the plasma completely independently of the carbon source, the ratio of the supply amount of the carbon and the metal catalyst does not change with time.

【0014】カーボン単層ナノチューブの生成時にアモ
ルファスカーボンやグラファイトも発生するが、これを
抑制する為には炭素に対してエッチング作用をもつ水素
や酸素を添加するとよい。またプラズマの一部に外部よ
りガスを供給することによって、プラズマ温度を急激に
下げ生成粉を急冷することができ、これによってもアモ
ルファスカーボンやグラファイトなど副生成物の生成を
抑制することができる。
Amorphous carbon and graphite are also generated when carbon single-walled nanotubes are formed. To suppress this, it is preferable to add hydrogen or oxygen which has an etching effect on carbon. Further, by supplying a gas to a part of the plasma from the outside, the plasma temperature can be rapidly lowered and the generated powder can be rapidly cooled, whereby the generation of by-products such as amorphous carbon and graphite can be suppressed.

【0015】さらに、カーボン単層ナノチューブを捕集
するための基板を、水冷などにより冷却することによ
り、多層のカーボンナノチューブの生成を抑制し、単層
のカーボンナノチューブを選択的に製造することができ
る。
Further, by cooling the substrate for collecting the carbon single-walled nanotubes by water cooling or the like, the production of multi-walled carbon nanotubes can be suppressed, and the single-walled carbon nanotubes can be selectively produced. .

【0016】[0016]

【発明の実施の形態】本発明による実施の一形態を以下
に説明する。
DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

【0017】本発明のカーボン単層ナノチューブ製造方
法は、無電極の高周波プラズマを用いるため、アーク放
電における電極の消耗の問題が原理的に無く、長時間運
転が可能である。
Since the method for producing single-walled carbon nanotubes of the present invention uses electrodeless high-frequency plasma, there is in principle no problem of electrode consumption due to arc discharge, and long-term operation is possible.

【0018】製造時に生成物の品質に時間的ばらつきが
生じないようにするには、炭素原料と触媒金属原料の一
定量をプラズマ中に定常的に供給すればよく、このため
には触媒金属は粉体の形でキャリアガスの定常流にのせ
て供給し、炭素原料は流量制御された炭化水素ガスの形
態でそれぞれ別に供給する。
In order to prevent the quality of the product from fluctuating with time during the production, a constant amount of the carbon raw material and the catalytic metal raw material may be constantly supplied into the plasma. The carrier gas is supplied in the form of powder in a steady flow of the carrier gas, and the carbon raw material is separately supplied in the form of a hydrocarbon gas whose flow rate is controlled.

【0019】本発明の実施の形態では、通常数百Tor
rの真空度でアーク領域のプラズマを発生させており、
この場合プラズマ中の原子の温度は1万℃の高温に達す
るため、供給した数μmの粒径をもつ触媒金属粉体はほ
ぼ完全に蒸発する。炭素原料である炭化水素ガスはプラ
ズマ内でさらに容易に原子化される。
In the embodiment of the present invention, usually several hundred Torr
Plasma in the arc region is generated at a degree of vacuum of r,
In this case, since the temperature of the atoms in the plasma reaches a high temperature of 10,000 ° C., the supplied catalytic metal powder having a particle size of several μm evaporates almost completely. Hydrocarbon gas, a carbon source, is more easily atomized in the plasma.

【0020】プラズマ内で原子化された炭素と触媒金属
は、プラズマ炎の周縁の低温部で凝集し微粒子を形成す
る。この微粒子上で触媒作用により、固溶していた炭素
原子又は飛来した炭素原子がカーボン単層ナノチューブ
を形成する。
The carbon and the catalyst metal atomized in the plasma aggregate at low temperatures around the periphery of the plasma flame to form fine particles. Due to the catalytic action on these fine particles, the carbon atoms that have dissolved or fly away form carbon single-walled nanotubes.

【0021】ただし、この時アモルファスカーボンやグ
ラファイトも形成されてしまうが、カーボン単層ナノチ
ューブの方が成長速度が速い為、炭素をエッチングする
水素や酸素を添加すれば、アモルファスやグラファイト
の方がより優先的にエッチングされ、品質の良いカーボ
ン単層ナノチューブが得られる。
However, at this time, amorphous carbon and graphite are also formed. However, since the growth rate of carbon single-walled nanotubes is higher, amorphous and graphite are more preferable if hydrogen or oxygen for etching carbon is added. Etching is preferentially performed, and a high-quality carbon single-walled nanotube is obtained.

【0022】また、微粒子が形成する場所であるプラズ
マ炎の周縁部に外部よりガスを供給し、プラズマの温度
を急激に低下させることにより、成長速度の遅いアモル
ファスカーボンやグラファイトが十分に形成されないま
ま、急冷によりそれらの反応を停止させ、品質の良いカ
ーボン単層ナノチューブを得ることができる。
Further, by supplying a gas from the outside to the peripheral portion of the plasma flame where the fine particles are formed and rapidly lowering the temperature of the plasma, amorphous carbon or graphite having a low growth rate is not sufficiently formed. The reaction can be stopped by quenching, and a high-quality carbon single-walled nanotube can be obtained.

【0023】更に、カーボン単層ナノチューブを捕集す
る基板を、水冷などにより冷却することにより、多層の
カーボンナノチューブの生成を抑制し、単層のカーボン
ナノチューブを選択的に製造することができる。
Further, by cooling the substrate for collecting the carbon single-walled nanotubes by water cooling or the like, it is possible to suppress the formation of multi-walled carbon nanotubes and selectively produce single-walled carbon nanotubes.

【0024】[0024]

【実施例】【Example】

実施例1 以下に、本発明の一実施例について、図1を参照して説
明する。
Example 1 An example of the present invention will be described below with reference to FIG.

【0025】本実施例では、高周波プラズマ発生装置に
おいて発振周波数4MHzで、約10kWの電力をコイ
ル3に供給することにより、300Torr程度の真空
度で数cmのサイズの高温プラズマ2を形成することが
できた。
In the present embodiment, the high-frequency plasma generator can generate a high-temperature plasma 2 having a size of several cm at a degree of vacuum of about 300 Torr by supplying approximately 10 kW of power to the coil 3 at an oscillation frequency of 4 MHz. did it.

【0026】プラズマの形状を安定させるため、図中上
方よりアルゴンガスを毎分約60リットルを供給し、プ
ラズマ内で発生した生成粉はこのガス流に乗って水冷さ
れた基板4まで達した後回収される。
In order to stabilize the shape of the plasma, about 60 liters of argon gas is supplied per minute from above in the figure, and the powder generated in the plasma reaches the water-cooled substrate 4 by riding this gas flow. Collected.

【0027】カーボン単層ナノチューブ合成のためには
金属触媒を必要とするため、本実施例では、触媒金属を
約3〜5μmの粒径をもつ粉体の形態で、流動式の粉体
供給装置により毎分3リットルでアルゴンのキャリアガ
ス気流にのせて、ノズル1を経てプラズマまで輸送し
た。
In order to synthesize a carbon single-walled nanotube, a metal catalyst is required. Therefore, in this embodiment, the catalyst metal is supplied in the form of a powder having a particle size of about 3 to 5 μm by a flow type powder supply apparatus. At a rate of 3 liters per minute in a carrier gas stream of argon, and transported to the plasma via the nozzle 1.

【0028】なお、このキャリアガスの流量が毎分1リ
ットルを下回る場合には、プラズマ内部に存在する逆向
きの気流によって、プラズマ中心部に粉体が供給されず
に触媒金属の蒸発が不十分であったので、本実施例では
キャリアガス流を毎分3リットルとした。
When the flow rate of the carrier gas is less than 1 liter per minute, the powder is not supplied to the center of the plasma due to the reverse airflow inside the plasma, and the catalytic metal is not sufficiently evaporated. Therefore, in this embodiment, the carrier gas flow was set to 3 liters per minute.

【0029】触媒金属の種類としては、鉄、コバルト、
ニッケルいずれの場合にもカーボン単層ナノチューブの
合成が可能であった。特にニッケル75%、コバルト2
5%の混合粉を用いたものが最もカーボン単層ナノチュ
ーブの収率が良かった。金属粉の標準的な供給量は毎分
約100mgであった。
The types of catalyst metals include iron, cobalt,
In each case of nickel, synthesis of carbon single-walled nanotubes was possible. Especially nickel 75%, cobalt 2
The one using 5% mixed powder had the highest yield of carbon single-walled nanotubes. The standard supply of metal powder was about 100 mg per minute.

【0030】炭素源としてメタンをプラズマ炎の下流側
の周縁部に毎分約1リットル供給した。なお、メタンを
供給する場所としてプラズマ炎の上流側を選んでも、毎
分1リットル程度の供給量であればプラズマの安定性を
損なわないため実用上問題は無かった。
As a carbon source, about 1 liter / minute of methane was supplied to the peripheral portion on the downstream side of the plasma flame. In addition, even if the upstream side of the plasma flame is selected as a place for supplying methane, if the supply rate is about 1 liter per minute, there is no practical problem since the stability of plasma is not impaired.

【0031】カーボン単層ナノチューブと共に形成され
るアモルファスカーボンやグラファイトの生成を抑制す
るため、プラズマの下流側に炭素に対しエッチング作用
をもつ水素を毎分6リットル供給した。メタンの供給量
に対する水素の供給量の比が2か3の場合は触媒金属微
粒子の周囲に多量のアモルファスやグラファイトが生成
したので、本実施例では水素の供給量の比が5を越える
ように選んだ。
In order to suppress the formation of amorphous carbon and graphite formed together with the single-walled carbon nanotubes, 6 liters of hydrogen having an etching effect on carbon was supplied to the downstream side of the plasma. When the ratio of the supply amount of hydrogen to the supply amount of methane is 2 or 3, since a large amount of amorphous or graphite was generated around the catalyst metal fine particles, in this embodiment, the ratio of the supply amount of hydrogen was set to exceed 5. I chose.

【0032】上記の方法により、プラズマ炎より多量の
微粒子が煤状に放出し、この微粒子が多くのカーボン単
層ナノチューブを含んでいることを電子顕微鏡により確
認した。ただしプラズマ炎に晒され1000℃程度の高
温にある基板上で微粒子を回収した場合には、カーボン
単層ナノチューブよりも2,3層でできた多層のカーボ
ンナノチューブの方が多く見られ、基板上でカーボンナ
ノチューブが直径方向に成長することが確認できた。従
って、単層ナノチューブのみを得るには、水冷などによ
り冷却された基板上で回収するとよい。
By the above method, it was confirmed by an electron microscope that a large amount of fine particles were released in a soot form from the plasma flame, and that the fine particles contained many carbon single-walled nanotubes. However, when the fine particles are collected on a substrate which is exposed to a plasma flame and is at a high temperature of about 1000 ° C., multi-walled carbon nanotubes composed of two or three layers are more frequently observed than single-walled carbon nanotubes. As a result, it was confirmed that the carbon nanotubes grew in the diameter direction. Therefore, in order to obtain only single-walled nanotubes, it is preferable to collect them on a substrate cooled by water cooling or the like.

【0033】実施例2 アモルファスカーボン及びグラファイトの生成を抑制す
るため、プラズマ下流部にアルゴンガスを毎分15リッ
トル供給した。アルゴンガス自身には炭素をエッチング
する作用は無いが、アルゴン導入に伴うプラズマの急冷
を行なうことにより、成長速度の速いカーボン単層ナノ
チューブを優先的に残し、他のアモルファスカーボンや
グラファイトの生成を抑えることができる。
Example 2 In order to suppress the formation of amorphous carbon and graphite, 15 liters of argon gas per minute was supplied to the downstream of the plasma. Although argon gas itself does not have an action of etching carbon, by rapidly cooling the plasma accompanying the introduction of argon, carbon single-walled nanotubes with a fast growth rate are preferentially left and the formation of other amorphous carbon and graphite is suppressed. be able to.

【0034】急冷の現象は、アルゴンガス導入時にプラ
ズマ下流部の輻射強度が低下したことから目視でも確認
できた。アルゴンを導入しない場合に比べ、触媒金属微
粒子の周囲に存在するアモルファスカーボンやグラファ
イトが少なくなり、特にグラファイトが著しく減少し
た。アモルファスカーボンが高温下で結晶性を改善しグ
ラファイトとなる過程をガス急冷が阻害したためと考え
られる。
The phenomenon of quenching could be confirmed visually because the radiation intensity of the downstream portion of the plasma was reduced when introducing argon gas. Compared to the case where argon was not introduced, the amount of amorphous carbon and graphite existing around the catalytic metal fine particles was reduced, and especially graphite was significantly reduced. It is considered that gas quenching hindered the process of improving the crystallinity of amorphous carbon at high temperatures to become graphite.

【0035】一方カーボン単層ナノチューブについて
は、その結晶性を電子顕微鏡で観察したところ、その結
晶性にガス冷却法が悪い影響を与えていないことを確認
した。
On the other hand, regarding the carbon single-walled nanotubes, the crystallinity was observed by an electron microscope, and it was confirmed that the gas cooling method did not adversely affect the crystallinity.

【0036】実施例3 市販で容易に入手できる金属粉は粒径のばら付きが大き
いため、触媒金属の原料に金属粉を用いた場合に、粒径
の大きな金属粉がプラズマ内で完全に蒸発しきれずに生
成物に混入して回収されてしまうことがある。
Example 3 Since commercially available metal powder has a large variation in particle diameter, when metal powder is used as a raw material for a catalytic metal, the metal powder having a large particle diameter is completely evaporated in plasma. In some cases, it is mixed with the product and collected.

【0037】これを防ぐ為には金属触媒源として有機金
属を用いた。本実施例では鉄の有機金属であるフェロセ
ンを用いた。フェロセンは昇崋温度が140℃と低いた
め、プラズマ中で完全に蒸発し、金属粉を用いた時のよ
うな未分解の原料粉は混入していなかった。
To prevent this, an organic metal was used as a metal catalyst source. In this example, ferrocene, which is an organic metal of iron, was used. Since ferrocene had a low assembling temperature of 140 ° C., it was completely evaporated in the plasma, and undecomposed raw material powder as when metal powder was used was not mixed.

【0038】フェロセンを触媒原料として用い炭素原料
としてメタンを用い、高効率にカーボン単層ナノチュー
ブを合成することが可能であった。
Using ferrocene as a catalyst raw material and methane as a carbon raw material, carbon single-walled nanotubes could be synthesized with high efficiency.

【0039】なおフェロセン自身にも炭素原子を含んで
いるため、メタンを用いずにフェロセンだけでも、収率
は悪いながらカーボン単層ナノチューブが合成できた。
Since ferrocene itself also contains a carbon atom, carbon single-walled nanotubes could be synthesized by using only ferrocene without using methane, although the yield was low.

【0040】[0040]

【発明の効果】従来のアーク放電によるカーボン単層ナ
ノチューブの製造方法では、電極である炭素棒が放電時
に消費され、更に電極に埋め込んだ触媒金属はその蒸気
圧の高さからより急激に消費される。炭素電極の消耗は
プラズマ状態に時間的変動を生じ、触媒金属の選択的な
蒸発はプラズマへの炭素と触媒金属の供給量の変動を生
じるため、カーボン単層ナノチューブの長時間合成は困
難であった。
According to the conventional method for producing single-walled carbon nanotubes by arc discharge, the carbon rod as the electrode is consumed during the discharge, and the catalytic metal embedded in the electrode is more rapidly consumed due to its high vapor pressure. You. The exhaustion of the carbon electrode causes a temporal change in the plasma state, and the selective evaporation of the catalyst metal causes a change in the supply amounts of the carbon and the catalyst metal to the plasma, so that it is difficult to synthesize carbon single-walled nanotubes for a long time. Was.

【0041】この課題を解決するため、本発明は図1で
示すような無電極プラズマ合成装置を用いた。これは4
MHzの高周波コイルにより最高温度が約1万℃の高温
プラズマを如何なる壁面にも接触させずに形成したもの
で、時間制限の無いカーボン単層ナノチューブの合成を
可能にした。
In order to solve this problem, the present invention uses an electrodeless plasma synthesis apparatus as shown in FIG. This is 4
A high-frequency plasma having a maximum temperature of about 10,000 ° C. was formed without contacting any wall surface by a high-frequency coil of MHz, so that it was possible to synthesize carbon single-walled nanotubes without any time limit.

【0042】触媒金属を数μmの粒径を持つ粉体の形態
で定常キャリアガス流に乗せて供給し、炭素原料はメタ
ンガスとしてガス流量計を介してプラズマに安定供給し
ている。金属触媒と炭素を別系統でプラズマへ供給すれ
ば、各成分元素の供給量比は一定で、品質の揃ったカー
ボン単層ナノチューブを合成することができる。
The catalyst metal is supplied in the form of a powder having a particle size of several μm in a steady carrier gas flow, and the carbon raw material is supplied as methane gas to the plasma stably via a gas flow meter. If the metal catalyst and carbon are supplied to the plasma in different systems, the supply ratio of each component element is constant, and carbon single-walled nanotubes of uniform quality can be synthesized.

【0043】プラズマ内で原子化された炭素と触媒金属
は、プラズマ周縁の低温部で凝集し生成粉を形成する
が、この時アモルファスカーボンやグラファイトも形成
されてしまう。そこで本発明では、カーボン単層ナノチ
ューブが他の相に比べ成長速度が速いことを利用し、炭
素をエッチングする水素や酸素を添加することによっ
て、アモルファスやグラファイトをより優先的にエッチ
ングし、品質の良いカーボン単層ナノチューブを得るこ
とが出来た。
The carbon atomized in the plasma and the catalyst metal are aggregated in a low-temperature portion on the periphery of the plasma to form a generated powder. At this time, amorphous carbon and graphite are also formed. Therefore, in the present invention, utilizing the fact that the growth rate of carbon single-walled nanotubes is higher than that of other phases, amorphous and graphite are more preferentially etched by adding hydrogen or oxygen for etching carbon, thereby improving quality. Good single-walled carbon nanotubes were obtained.

【0044】同じ効果を狙った他の手法としては、プラ
ズマ周縁部に外部よりアルゴンガスを供給し、プラズマ
の温度を急激に低下させることにより、成長速度の遅い
アモルファスカーボンやグラファイトが十分に形成され
ない段階で、急冷により反応を停止させ、品質の良いカ
ーボン単層ナノチューブを得ることが出来た。
Another method aiming at the same effect is to supply an argon gas from the outside to the periphery of the plasma and rapidly lower the temperature of the plasma, so that amorphous carbon or graphite having a low growth rate cannot be sufficiently formed. At this stage, the reaction was stopped by rapid cooling, and a high-quality carbon single-walled nanotube was obtained.

【0045】また、冷却された捕集基板を用いれば、複
数層のカーボンナノチューブの生成を抑え単層カーボン
ナノチューブを選択的に得ることができる。
When a cooled collecting substrate is used, the production of a plurality of layers of carbon nanotubes can be suppressed and single-walled carbon nanotubes can be selectively obtained.

【図面の簡単な説明】[Brief description of the drawings]

【図1】本発明の高周波プラズマによるカーボン単層ナ
ノチューブ製造装置の概念図である。
FIG. 1 is a conceptual diagram of an apparatus for producing single-walled carbon nanotubes using high-frequency plasma according to the present invention.

【符号の説明】[Explanation of symbols]

1 粉体供給ポート 2 プラズマ 3 高周波コイル 4 捕集基板 DESCRIPTION OF SYMBOLS 1 Powder supply port 2 Plasma 3 High frequency coil 4 Collection board

Claims (8)

【特許請求の範囲】[Claims] 【請求項1】 無電極の高周波プラズマを用いてプラズ
マを発生させ、炭素原料と金属触媒を前記プラズマ中に
供給することを特徴とするカーボン単層ナノチューブの
製造方法。
1. A method for producing single-walled carbon nanotubes, comprising generating plasma using an electrodeless high-frequency plasma and supplying a carbon material and a metal catalyst into the plasma.
【請求項2】 無電極の高周波プラズマを用いてプラズ
マを発生させ、炭素原料と金属触媒を別々に前記プラズ
マ中に供給することを特徴とするカーボン単層ナノチュ
ーブの製造方法。
2. A method for producing carbon single-walled nanotubes, wherein plasma is generated using an electrodeless high-frequency plasma, and a carbon material and a metal catalyst are separately supplied into the plasma.
【請求項3】 前記炭素原料として炭化水素ガスを用い
ることを特徴とする請求項1または請求項2記載のカー
ボン単層ナノチューブの製造方法。
3. The method according to claim 1, wherein a hydrocarbon gas is used as the carbon raw material.
【請求項4】 粉体状の金属触媒を前記プラズマ中に供
給することを特徴とする請求項1または請求項2記載の
カーボン単層ナノチューブの製造方法。
4. The method according to claim 1, wherein a powdery metal catalyst is supplied into the plasma.
【請求項5】 前記炭素原料および前記金属触媒として
有機金属を用いることを特徴とする請求項1記載のカー
ボン単層ナノチューブの製造方法。
5. The method according to claim 1, wherein an organic metal is used as the carbon raw material and the metal catalyst.
【請求項6】 前記プラズマ中に、炭素をエッチングす
るガスを供給することを特徴とする請求項1または請求
項2または請求項3または請求項4または請求項5記載
のカーボン単層ナノチューブの製造方法。
6. The method for producing a carbon single-walled nanotube according to claim 1, wherein a gas for etching carbon is supplied into the plasma. Method.
【請求項7】 前記プラズマ領域の温度を局所的に低下
させることを特徴とする請求項1または請求項2または
請求項3または請求項4または請求項5記載のカーボン
単層ナノチューブの製造方法。
7. The method of claim 1, wherein the temperature of the plasma region is locally reduced.
【請求項8】 カーボンナノチューブを捕集する基板が
冷却されていることを特徴とする、請求項1または請求
項2または請求項3または請求項4または請求項5また
は請求項6または請求項7記載のカーボンナノチューブ
の製造方法。
8. The substrate for collecting carbon nanotubes is cooled, wherein the substrate for cooling the carbon nanotubes is cooled. A method for producing the carbon nanotube according to the above.
JP8003636A 1996-01-12 1996-01-12 Method for producing carbon single-walled nanotube Expired - Fee Related JP2737736B2 (en)

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