JP2005350285A - Carbon nanotube, carbon nanowire, and carbon nanoonion - Google Patents

Carbon nanotube, carbon nanowire, and carbon nanoonion Download PDF

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JP2005350285A
JP2005350285A JP2004170379A JP2004170379A JP2005350285A JP 2005350285 A JP2005350285 A JP 2005350285A JP 2004170379 A JP2004170379 A JP 2004170379A JP 2004170379 A JP2004170379 A JP 2004170379A JP 2005350285 A JP2005350285 A JP 2005350285A
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silicon carbide
carbon nanotubes
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JP4615900B2 (en
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Masasuke Takada
雅介 高田
Takashi Kawamoto
昂 川本
Tomoichiro Okamoto
智一郎 岡元
Shigeru Matsuura
茂 松浦
Kenji Ogawa
賢治 小川
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Taiheiyo Cement Corp
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<P>PROBLEM TO BE SOLVED: To provide a method by which highly crystalline carbon nanotubes can be produced in a large amount; and a method capable of producing carbon nanowires and carbon nanoonions in parallel with the synthesis of the carbon nanotubes. <P>SOLUTION: An electric current is made to flow on a sintered compact or a formed body mainly comprising silicon carbide under vacuum, so that the sintered compact or the formed body is heated and fusion-cut by generated Joule heat. Multilayer carbon nanotubes, carbon nanowires, or carbon nanoonions are synthesized in a cathode evaporant being a byproduct which is produced when silicon carbide is pyrolyzed by vacuum arc discharge generated between fusion-cut silicon carbides. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、カーボンナノチューブ、カーボンナノワイヤおよびカーボンナノオニオンの製造方法に関する。   The present invention relates to a method for producing carbon nanotubes, carbon nanowires, and carbon nano-onions.

カーボンナノチューブは、六角網目状のグラフェンシートを円筒状に巻いた単層もしくは多層のチューブ状物質であり、その導電性、熱伝導性、電子放出特性、高強度、高潤滑性、化学的安定性等の様々な特徴的な機能を有する。このため、カーボンナノチューブは、幅広い用途への利用に期待が集まっており、例えば、ＳＴＭやＡＦＭ用探針、表示素子、ディスプレイ等の電界放出電子源などへの用途展開が期待されている。   A carbon nanotube is a single-layer or multi-layer tube-like material in which hexagonal mesh graphene sheets are wound in a cylindrical shape, and its conductivity, thermal conductivity, electron emission characteristics, high strength, high lubricity, and chemical stability Etc. have various characteristic functions. For this reason, carbon nanotubes are expected to be used for a wide range of applications. For example, application development to field emission electron sources such as STM and AFM probes, display elements, and displays is expected.

カーボンナノチューブの主な合成法としては、直流アーク放電法、レーザ蒸発法、化学気相成長法などが知られている（例えば、非特許文献１）。   As main synthesis methods of carbon nanotubes, a direct current arc discharge method, a laser evaporation method, a chemical vapor deposition method and the like are known (for example, Non-Patent Document 1).

直流アーク放電法では、大気圧よりやや低い圧力のアルゴンや水素雰囲気下、炭素棒の間に２０Ｖ、５０Ａ程度のアーク放電を行うことによって、陰極堆積物の中に多層カーボンナノチューブが生成される。このアーク放電法では結晶性の高い多層カーボンナノチューブが得られる。   In the direct current arc discharge method, multi-walled carbon nanotubes are generated in the cathode deposit by performing an arc discharge of about 20 V and 50 A between carbon rods in an argon or hydrogen atmosphere at a pressure slightly lower than atmospheric pressure. With this arc discharge method, multi-walled carbon nanotubes with high crystallinity can be obtained.

化学気相成長法は、炭素源となる炭素化合物を５００〜１０００℃で触媒金属微粒子と接触させることによりカーボンナノチューブを得る方法である。この化学気相成長法では、触媒金属の種類およびその配置の仕方、炭素化合物の種類などに種々のバリエーションを持つカーボンナノチューブの合成が可能である。   The chemical vapor deposition method is a method of obtaining carbon nanotubes by bringing a carbon compound serving as a carbon source into contact with catalytic metal fine particles at 500 to 1000 ° C. In this chemical vapor deposition method, it is possible to synthesize carbon nanotubes having various variations in the type of catalyst metal, the manner of arrangement thereof, the type of carbon compound, and the like.

レーザ蒸発法は、ニッケル／コバルトなどの触媒を混ぜた炭素にレーザの強いパルス光を照射することによって、比較的高い純度の単層カーボンナノチューブを得る事ができる。このレーザ蒸発法では、条件変更によりチューブ径の制御が可能であるが、生産性は低いことから、主に研究用に限定された手法である。   In the laser evaporation method, single-walled carbon nanotubes having a relatively high purity can be obtained by irradiating carbon mixed with a catalyst such as nickel / cobalt with intense pulsed light of a laser. In this laser evaporation method, the tube diameter can be controlled by changing the conditions. However, since the productivity is low, this method is mainly limited to research.

なお、上記の方法以外にも、特殊な製造方法として、炭化ケイ素の結晶を、高温真空中で残留酸素によるSi（シリコン）の脱離（SiO）により、表面に残ったC（炭素）がナノチューブ構造に変化することによって配向性の高いカーボンナノチューブを合成する炭化ケイ素表面分解法が提案されている。   In addition to the above method, as a special manufacturing method, a silicon carbide crystal is formed by removing C (carbon) from the surface of the silicon carbide by desorption (SiO) of residual silicon (oxygen) in high temperature vacuum. A silicon carbide surface decomposition method for synthesizing highly oriented carbon nanotubes by changing to a structure has been proposed.

一方、カーボンナノワイヤの製造方法については、所定の圧力下、水素ガスを導入した真空チャンバー内で、黒鉛製の陽極／陰極間にアーク放電を発生させる方法が提案されている（例えば、特許文献１）。
特開２００４−２１０３号公報（特許請求の範囲、請求項２など） 「科学技術動向 ２００１年７月号 特集 カーボンナノチューブ製造技術開発の動向」（文部科学省科学技術政策研究所 科学技術動向研究センター） On the other hand, as a method for producing carbon nanowires, a method has been proposed in which arc discharge is generated between an anode / cathode made of graphite in a vacuum chamber into which hydrogen gas is introduced under a predetermined pressure (for example, Patent Document 1). ).
JP 2004-2103 A (Claims, Claim 2 etc.) "Science and Technology Trends July 2001 Special Issue Trends in Carbon Nanotube Manufacturing Technology Development" (Ministry of Education, Culture, Sports, Science and Technology, Research Center for Science and Technology Policy)

結晶性が高い多層カーボンナノチューブの作製には、直流アーク放電が優れているが、アーク放電法は一般に生産性が低いという課題がある。一方、化学気相成長法は、原料をガスとして供給出来るために大量合成に最も向いている手法と言われているが、合成されたカーボンナノチューブは一般に欠陥が多い。そこで、結晶性の高い好適なカーボンナノチューブの生産性を高める製造方法が必要とされていた。   Although DC arc discharge is excellent for producing multi-walled carbon nanotubes with high crystallinity, the arc discharge method has a problem that productivity is generally low. On the other hand, the chemical vapor deposition method is said to be the most suitable method for mass synthesis because the raw material can be supplied as a gas, but the synthesized carbon nanotubes generally have many defects. Therefore, a production method for increasing the productivity of suitable carbon nanotubes with high crystallinity has been required.

また、従来、カーボンナノチューブとカーボンナノワイヤは異なる方法で別々に合成されてきたが、これらを一貫したプロセスで合成する方法は未だ提案されていない。   Conventionally, carbon nanotubes and carbon nanowires have been synthesized separately by different methods, but a method for synthesizing them by a consistent process has not yet been proposed.

本発明は、上述した従来技術の問題点に鑑みてなされたものであり、結晶性の高いカーボンナノチューブを多量に製造できる方法を提供することを目的とする。また、カーボンナノチューブの合成と並行してカーボンナノワイヤ、カーボンナノオニオンも製造できる方法を提供することを目的とする。   The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a method capable of producing a large amount of highly crystalline carbon nanotubes. Another object of the present invention is to provide a method capable of producing carbon nanowires and carbon nano-onions in parallel with the synthesis of carbon nanotubes.

上記課題を解決するため、本発明の第１の観点によれば、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノチューブを合成することを特徴とする、カーボンナノチューブの製造方法が提供される。   In order to solve the above problems, according to a first aspect of the present invention, an electric current is passed over a sintered body or molded body mainly composed of silicon carbide, and the sintered body or the molded body is caused by Joule heat generated. There is provided a method for producing carbon nanotubes, characterized by synthesizing carbon nanotubes by heating and fusing.

また、本発明の第２の観点によれば、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノワイヤを合成することを特徴とする、カーボンナノワイヤの製造方法が提供される。   According to the second aspect of the present invention, an electric current is passed over a sintered body or molded body mainly composed of silicon carbide, and the sintered body or the molded body is heated and melted by the generated Joule heat. Thus, a method for producing carbon nanowires, characterized in that carbon nanowires are synthesized, is provided.

さらに、本発明の第３の観点によれば、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノチューブおよびカーボンナノワイヤを合成することを特徴とする、カーボンナノチューブおよびカーボンナノワイヤの製造方法が提供される。   Furthermore, according to the third aspect of the present invention, an electric current is passed over a sintered body or molded body mainly composed of silicon carbide, and the sintered body or the molded body is heated and melted by the generated Joule heat. Thus, a method for producing carbon nanotubes and carbon nanowires, characterized in that carbon nanotubes and carbon nanowires are synthesized, is provided.

またさらに、本発明の第４の観点によれば、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノオニオンを合成することを特徴とする、カーボンナノオニオンの製造方法が提供される。   Still further, according to the fourth aspect of the present invention, an electric current is passed over the sintered body or molded body mainly composed of silicon carbide, and the sintered body or the molded body is heated by the generated Joule heat to be melted. Thus, a method for producing carbon nano-onions is provided, which is characterized by synthesizing carbon nano-onions.

本発明によれば、結晶性の高い多層カーボンナノチューブやカーボンナノワイヤを多量に製造することが可能であり、さらにはカーボンナノオニオンも製造できる。また、カーボンナノワイヤを多層カーボンナノチューブの合成と並行して製造することも可能になる。   According to the present invention, it is possible to produce a large amount of multi-walled carbon nanotubes and carbon nanowires with high crystallinity, and it is also possible to produce carbon nano-onions. Moreover, it becomes possible to manufacture carbon nanowires in parallel with the synthesis of multi-walled carbon nanotubes.

以下に本発明の詳細について説明する。
本発明方法によるカーボンナノチューブの製造は、好ましくは、例えば真空下において、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより実施される。溶断した炭化ケイ素間に発生する真空アーク放電により、炭化ケイ素を熱分解させたときの副産物である陰極蒸発物において多層カーボンナノチューブが合成される。 Details of the present invention will be described below.
In the production of the carbon nanotube by the method of the present invention, preferably, for example, under a vacuum, an electric current is passed over a sintered body or a molded body mainly composed of silicon carbide, and the sintered body or the molded body is caused by Joule heat generated. It is carried out by heating and fusing. Multi-walled carbon nanotubes are synthesized in the cathode evaporant, which is a byproduct when silicon carbide is thermally decomposed, by vacuum arc discharge generated between blown silicon carbide.

また、本発明方法によるカーボンナノワイヤの製造は、好ましくは、例えば真空下において、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより実施される。溶断した炭化ケイ素間に発生する真空アーク放電により、炭化ケイ素を熱分解させたときの副産物である陰極蒸発物においてカーボンナノワイヤが合成される。   In addition, the production of the carbon nanowire by the method of the present invention is preferably performed by passing an electric current over a sintered body or a molded body mainly composed of silicon carbide under a vacuum, for example, by the generated Joule heat. It is carried out by heating the body to melt it. Carbon nanowires are synthesized in the cathode evaporant, which is a by-product when silicon carbide is thermally decomposed, by vacuum arc discharge generated between blown silicon carbide.

また、本発明方法によるカーボンナノオニオンの製造は、好ましくは、例えば真空下において、炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより実施される。溶断した炭化ケイ素間に発生する真空アーク放電により、炭化ケイ素を熱分解させたときの副産物である陰極蒸発物においてカーボンナノオニオンが合成される。カーボンナノオニオンは、フラーレンの周りに何層ものグラファイト層が同心円上に閉殻構造をとった球状粒子である。   In addition, the production of carbon nano-onion by the method of the present invention is preferably performed by passing an electric current over a sintered body or a molded body mainly composed of silicon carbide under a vacuum, for example, by the generated Joule heat. It is carried out by heating the molded body and fusing it. Carbon nano-onions are synthesized in the cathode evaporant, which is a byproduct when silicon carbide is thermally decomposed, by vacuum arc discharge generated between blown silicon carbide. Carbon nano-onion is a spherical particle in which a number of graphite layers have a closed shell structure on concentric circles around fullerene.

本発明においては原料として炭化ケイ素を主体とする焼結体または成形体が使用される。炭化ケイ素としては、適度な導電性を有する点から、少量の金属ケイ素を含有する焼結体が好ましい。その意味から反応焼結法による炭化ケイ素焼結体が好適である。あまり高純度の炭化ケイ素焼結体は好ましくない。さらに、焼結体としてＳｉＣを主体とする３次元網目構造を有する多孔質体を使用することも好適である。   In the present invention, a sintered body or a molded body mainly composed of silicon carbide is used as a raw material. As silicon carbide, a sintered body containing a small amount of metallic silicon is preferable from the viewpoint of appropriate conductivity. In this sense, a silicon carbide sintered body obtained by a reactive sintering method is preferable. A very high purity silicon carbide sintered body is not preferable. Furthermore, it is also preferable to use a porous body having a three-dimensional network structure mainly composed of SiC as a sintered body.

焼結体または成形体の形状は任意であるが、試料形状を線材状とすることが好ましい。試料の成形は、例えば、焼成前の成形段階で線材状に成形してもよいし、成形体から加工により線材状のものを切り出してもよく、また、焼結体に機械加工を施すことで線材状試料を得てもよい。試料形状を線材状とする理由は、後述するように、その長さ方向に所定の電流を流す場合に、断面積が大きい棒状や板状であると、より大きな電流を流す必要が生じ、装置コストや安全性等の点でデメリットが生ずる場合があるからである。ただし、製造規模などに応じて、線材状以外の任意の形状を採用できることは言うまでもない。   Although the shape of a sintered compact or a molded object is arbitrary, it is preferable to make a sample shape into a wire form. For example, the sample may be formed into a wire shape in the forming stage before firing, or a wire-like material may be cut out from the formed body by processing, and the sintered body may be machined. A wire-like sample may be obtained. The reason why the sample shape is a wire shape is that, as will be described later, when a predetermined current is flowed in the length direction, if the cross-sectional area is a rod shape or plate shape, it is necessary to flow a larger current. This is because there may be disadvantages in terms of cost and safety. However, it goes without saying that any shape other than the wire shape can be adopted according to the manufacturing scale.

得られた線材状試料の端面に金属電極を形成し、通電試料とする。そして、真空から大気圧までの所定の圧力条件（好ましくは真空条件）で通電試料の電極間に所定の電流を流すことによりジュール熱を発生させ、このジュール熱により通電試料そのものを加熱する。金属電極は、好ましくは、ステンレスによる圧着、もしくは白金（Ｐｔ）等の貴金属ペーストを塗布して、焼き付けることにより形成される。なお、金属電極は、例えばスパッタ法等により形成することも可能である。また、形成された金属電極には、銀線や白金線等を用いてリード線を設けることが好ましい。   A metal electrode is formed on the end face of the obtained wire-like sample to obtain an energized sample. Then, Joule heat is generated by flowing a predetermined current between electrodes of the energized sample under a predetermined pressure condition (preferably vacuum condition) from vacuum to atmospheric pressure, and the energized sample itself is heated by this Joule heat. The metal electrode is preferably formed by crimping with stainless steel or applying a precious metal paste such as platinum (Pt) and baking it. The metal electrode can also be formed by, for example, sputtering. The formed metal electrode is preferably provided with a lead wire using a silver wire, a platinum wire or the like.

以上のようにして設定された炭化ケイ素試料の両端に電圧をかけ、一定電流を流す。通電は、通電試料に溶断を生じさせるまで行う。この通電時の雰囲気は真空にすることが好ましい。真空中で通電加熱された炭化ケイ素試料は、ジュール熱により次第に高温になる。高温になると、まず炭化ケイ素内に含まれるＳｉが分解、消失し、炭化ケイ素粒からなるポーラスな構造になる。その結果、導電率が低下し、一定電流を保つための印加電圧が増大し、さらに温度が上がり、最終的に溶断が起こる。溶断直前には、印加電圧が初期に比べおよそ４０％以上も上昇する。   A voltage is applied to both ends of the silicon carbide sample set as described above to allow a constant current to flow. The energization is performed until the energized sample is melted. The atmosphere during energization is preferably a vacuum. A silicon carbide sample that is electrically heated in a vacuum gradually becomes high temperature due to Joule heat. When the temperature rises, first, Si contained in the silicon carbide is decomposed and disappears, resulting in a porous structure made of silicon carbide particles. As a result, the electrical conductivity decreases, the applied voltage for maintaining a constant current increases, the temperature rises, and finally fusing occurs. Immediately before fusing, the applied voltage rises by about 40% or more compared to the initial level.

試料は溶断する直前に炭化ケイ素の融点より高温の数千度に達すると考えられる。このため、炭化ケイ素は分解し、Ｓｉ成分が蒸発してカーボンに富んだ組成になる。特に溶断部位の負極側でＳｉ成分が蒸発して細孔が形成されることから、溶断直前に真空アーク放電が発生する。このカーボンに富んだ組成部位に生じたギャップ間のアーク放電により、飛散物質の中にカーボンナノチューブやカーボンナノワイヤ、カーボンナノオニオンが生成するものと推測される。   It is considered that the sample reaches several thousand degrees higher than the melting point of silicon carbide just before fusing. For this reason, silicon carbide is decomposed and the Si component is evaporated, resulting in a carbon-rich composition. In particular, since the Si component evaporates and pores are formed on the negative electrode side of the fusing site, vacuum arc discharge occurs immediately before fusing. It is presumed that carbon nanotubes, carbon nanowires, and carbon nano-onions are generated in the scattered material by the arc discharge between the gaps generated in the carbon-rich composition site.

カーボンに富んだ組成部位に生じたギャップの距離によって生成する物質は異なり、ギャップが小さい場合は、カーボンナノチューブが生成し、ギャップが大きくなるとカーボンナノワイヤが生成する。このことから、ギャップの大小を調節することによって、カーボンナノチューブとカーボンナノワイヤを区別して作ることが可能になる。ギャップの大小は、例えば、試料中のＳｉ濃度や、印加電圧、通電時間などの通電条件を調節することによって制御できる。   Substances generated vary depending on the gap distance generated in the carbon-rich composition site. When the gap is small, carbon nanotubes are generated, and when the gap is increased, carbon nanowires are generated. From this, it becomes possible to distinguish between carbon nanotubes and carbon nanowires by adjusting the size of the gap. The size of the gap can be controlled, for example, by adjusting energization conditions such as Si concentration in the sample, applied voltage, and energization time.

生成するカーボンナノチューブは種々の形状を有するが、鋭端部が円錐状であって、鋭端部の角度が４５°以下である、電界放出電子源として有用なカーボンナノチューブも多数生成させることが可能である。
なお、炭化ケイ素を主体とする焼結体または成形体中の不純物として、例えば、鉄やコバルトなどの触媒として働く成分を意図的に添加することによって、単層のカーボンナノチューブを生成させることも可能である。 The carbon nanotubes to be generated have various shapes, but it is possible to generate many carbon nanotubes that are useful as field emission electron sources with a sharp end at a conical shape and an angle at the sharp end of 45 ° or less. It is.
In addition, it is also possible to generate single-walled carbon nanotubes by intentionally adding a component that acts as a catalyst such as iron or cobalt as an impurity in a sintered body or molded body mainly composed of silicon carbide. It is.

溶断により生成した飛散物質中には、合成されたカーボンナノチューブ、カーボンナノワイヤ、またはカーボンナノオニオンの１種以上が存在する。このため、該飛散物質を回収することによって、目的のカーボンナノチューブ、カーボンナノワイヤ、またはカーボンナノオニオンを得ることができる。   One or more types of synthesized carbon nanotubes, carbon nanowires, or carbon nano-onions are present in the scattered material generated by fusing. For this reason, the target carbon nanotube, carbon nanowire, or carbon nano-onion can be obtained by collecting the scattered material.

本発明の好ましい態様においては、カーボンナノチューブとカーボンナノワイヤを連続的に製造することが可能である。例えば、放電ギャップが増大してＳｉＣの熱分解生成物の放出量が減少し、アーク温度が上昇すると、多層カーボンナノチューブの中心線上に炭素原子チェーンの生成が促進される結果、引き続きカーボンナノワイヤが生成してくるものと考えられる。   In a preferred embodiment of the present invention, it is possible to continuously produce carbon nanotubes and carbon nanowires. For example, if the discharge gap increases, the amount of SiC pyrolysis products released decreases, and the arc temperature rises, the formation of carbon atom chains on the centerline of multi-walled carbon nanotubes is promoted, resulting in the continued generation of carbon nanowires. It is thought that it will do.

以下、実施例を挙げ、本発明をさらに詳細に説明するが、本発明はこれによって制約されるものではない。
（実施例１）
図１に示す製造装置１を用いて、カーボンナノチューブ、カーボンナノワイヤおよびカーボンナノオニオンを製造した。反応焼結法で作製された炭化ケイ素板（密度３.０８ｇ／ｃｍ3）から線材状試料３（外形寸法１ｍｍ×１ｍｍ×１５ｍｍ）を切り出し、その両端に銀線７をつないで通電試料とした。この通電試料を、図１に示す製造装置１において、石英ガラス管２内に水平に設置した。この製造装置１では、Ｔ字状の石英ガラス管２内において、線材状試料３に近接して該飛散物回収のためのＴａプレート４が配備されている。また石英ガラス管２内のガスは、排気バルブ５の開閉により外気と流通・遮断できるように構成した。 EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited by this.
(Example 1)
Carbon nanotubes, carbon nanowires, and carbon nano-onions were produced using the production apparatus 1 shown in FIG. A wire-like sample 3 (external dimensions 1 mm × 1 mm × 15 mm) was cut out from a silicon carbide plate (density 3.08 g / cm 3 ) produced by the reaction sintering method, and a silver wire 7 was connected to both ends to form an energized sample. . This energized sample was placed horizontally in the quartz glass tube 2 in the manufacturing apparatus 1 shown in FIG. In this manufacturing apparatus 1, a Ta plate 4 is provided in the T-shaped quartz glass tube 2 in the vicinity of the wire-like sample 3 for collecting the scattered matter. Further, the gas in the quartz glass tube 2 was configured to be able to flow and shut off from the outside air by opening and closing the exhaust valve 5.

次に、１.４×１０２パスカル（Ｐａ）の真空下で電極端子に直流定電流源６を接続し、１７Ａの直流電流で通電を行った。時間とともに１７Ａの通電を維持するための印加電圧が増大し、１３分後に線材状試料３は溶断した。通電開始後４分間は印加電圧と線材状試料３の表面温度はともに一定であったが、溶断直前に印加電圧は、初期に比べ約４３％増大し、線材状試料３はより高温になった。溶断部位を走査型電子顕微鏡（ＳＥＭ）で観察した結果を図２および図３に示す。図２は溶断部の負極側、図３は正極側を示している。負極側には、Ｓｉ成分の蒸発によって形成された孔があいており、溶断直後に真空アーク放電が発生したものと考えられた。 Next, a DC constant current source 6 was connected to the electrode terminal under a vacuum of 1.4 × 10 2 Pascal (Pa), and energization was performed with a DC current of 17A. The applied voltage for maintaining the 17A energization increased with time, and the wire-like sample 3 was melted after 13 minutes. The applied voltage and the surface temperature of the wire-like sample 3 were both constant for 4 minutes after the start of energization, but the applied voltage increased by about 43% immediately before the fusing, and the wire-like sample 3 became higher in temperature. . The results of observing the fusing site with a scanning electron microscope (SEM) are shown in FIGS. FIG. 2 shows the negative electrode side of the fusing part, and FIG. 3 shows the positive electrode side. There was a hole formed by evaporation of the Si component on the negative electrode side, and it was considered that a vacuum arc discharge occurred immediately after fusing.

また、図４に示すように、線材状試料３を溶断部ａ、溶断部近傍ｂ、中央部ｃ、中央部ｄおよび負極近傍ｅの５つの領域に分け、各領域ごとにＥＤＳ測定を行った。通電後の線材状試料３には、Ｓｉ酸化物が形成されている可能性があるため、Ｓｉ、Ｃ、Ｏの３元素について、ＺＡＦ法を用いて定量を行った。その結果を表１に示す。   Further, as shown in FIG. 4, the wire-like sample 3 was divided into five regions, namely, a fused portion a, a fused portion vicinity b, a central portion c, a central portion d, and a negative electrode vicinity e, and EDS measurement was performed for each region. . Since there is a possibility that Si oxide is formed in the wire-like sample 3 after energization, the three elements of Si, C, and O were quantified using the ZAF method. The results are shown in Table 1.

Figure 2005350285
Figure 2005350285

以上の測定から、高温となる溶断部ａに近づくにつれてＳｉが減り、Ｃの量が増えていくことが判った。また、溶断面に存在する物質のほとんどがカーボンであることが判明した。   From the above measurement, it was found that Si decreased and the amount of C increased as it approached the melted part a that became high temperature. It has also been found that most of the substances present in the melting section are carbon.

溶断時の飛散物質を回収し、透過電子顕微鏡（ＴＥＭ）で観察したものが、図５である。この図５から、多数の多層カーボンナノチューブあるいはカーボンナノワイヤが生成しているのがわかる。このうちカーボンナノチューブを拡大した像が図６である。本実施例では、外径が約２７ｎｍ、内径約４ｎｍ、３７層の多層カーボンナノチューブが生成した。また、図７には拡大したカーボンナノワイヤを示した。これは外径約１４ｎｍ、４０層のカーボンナノワイヤであった。さらに、溶断時の飛散物質中には、フラーレンの周りに何層ものグラファイト層が同心円上に閉殻構造をとったカーボンナノオニオンの生成も確認された。カーボンナノオニオンの透過電子顕微鏡（ＴＥＭ）写真を図８に示す。   FIG. 5 shows the scattered material collected at the time of fusing and observed with a transmission electron microscope (TEM). FIG. 5 shows that a large number of multi-walled carbon nanotubes or carbon nanowires are generated. An enlarged image of the carbon nanotube is shown in FIG. In this example, multi-walled carbon nanotubes having an outer diameter of about 27 nm, an inner diameter of about 4 nm, and 37 layers were generated. FIG. 7 shows an enlarged carbon nanowire. This was a carbon nanowire with an outer diameter of about 14 nm and 40 layers. Furthermore, it was also confirmed that carbon nano-onions were formed in the scattered material at the time of fusing, in which many graphite layers had a closed shell structure on a concentric circle around fullerene. A transmission electron microscope (TEM) photograph of the carbon nano-onion is shown in FIG.

本発明により製造される多層カーボンナノチューブは、例えばＳＴＭやＡＦＭ用探針、表示素子、ディスプレイ等の電界放出電子源などとして有用であり、また、カーボンナノワイヤ、カーボンナノオニオンは、例えば、機械構造材料、電子部品、光半導体など広範な分野で利用可能なものである。   The multi-walled carbon nanotube produced by the present invention is useful as a field emission electron source such as a probe for STM or AFM, a display element, a display, etc. Further, carbon nanowires and carbon nano-onions are, for example, mechanical structural materials It can be used in a wide range of fields such as electronic parts and optical semiconductors.

通電加熱法による製造装置のセッティング状態を示す図面。Drawing which shows the setting state of the manufacturing apparatus by an electric heating method. 溶断部の負極側のＳＥＭ像を示す写真。The photograph which shows the SEM image of the negative electrode side of a fusing part. 溶断部の正極側のＳＥＭ像を示す写真。The photograph which shows the SEM image of the positive electrode side of a fusing part. ＥＤＳ測定における測定部位を示す模式図。The schematic diagram which shows the measurement site | part in an EDS measurement. 飛散物質のＴＥＭ像を示す写真。The photograph which shows the TEM image of a scattering material. 多層カーボンナノチューブのＴＥＭ像を示す写真。The photograph which shows the TEM image of a multi-walled carbon nanotube. 多層カーボンナノワイヤのＴＥＭ像を示す写真。The photograph which shows the TEM image of a multilayer carbon nanowire. カーボンナノオニオンのＴＥＭ像を示す写真。The photograph which shows the TEM image of carbon nano onion.

符号の説明Explanation of symbols

１ 製造装置
２ 石英ガラス管
３ 線材状試料
４ Ｔａプレート
５ 排気バルブ
６ 直流定電流源
７ 銀線 DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 2 Quartz glass tube 3 Wire-like sample 4 Ta plate 5 Exhaust valve 6 DC constant current source 7 Silver wire

Claims (4)

炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノチューブを合成することを特徴とする、カーボンナノチューブの製造方法。   Carbon nanotubes are synthesized by passing an electric current over a sintered body or molded body mainly composed of silicon carbide, and heating and melting the sintered body or the molded body by Joule heat generated. And carbon nanotube manufacturing method. 炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノワイヤを合成することを特徴とする、カーボンナノワイヤの製造方法。   Carbon nanowires are synthesized by passing an electric current over a sintered body or molded body mainly composed of silicon carbide, and heating and melting the sintered body or the molded body by generated Joule heat. The manufacturing method of carbon nanowire. 炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノチューブおよびカーボンナノワイヤを合成することを特徴とする、カーボンナノチューブおよびカーボンナノワイヤの製造方法。   Synthesizing carbon nanotubes and carbon nanowires by passing an electric current over a sintered body or molded body mainly composed of silicon carbide, and heating the sintered body or the molded body by generated Joule heat to melt it. A method for producing carbon nanotubes and carbon nanowires. 炭化ケイ素を主体とする焼結体または成形体上に電流を流し、発生するジュール熱によって前記焼結体または前記成形体を加熱して溶断させることにより、カーボンナノオニオンを合成することを特徴とする、カーボンナノオニオンの製造方法。   A carbon nano-onion is synthesized by passing an electric current over a sintered body or a molded body mainly composed of silicon carbide, and heating the sintered body or the molded body by Joule heat to be blown out. A method for producing carbon nano-onions.
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