JP2004189573A - Carbon nanotube aggregate, and carbon nanotube setting device with the same set therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-length carbon nanotube (CNT) fiber having excellent electron emission properties and mechanical strength, to provide a CNT (carbon nanotube) aggregate with desired dimensions in which the CNT fibers are sufficiently entangled each other, and to provide a CNT-setting device in which the CNT aggregate is set. <P>SOLUTION: The CNT aggregate is formed in such a manner that a plurality of carbon nanotubes are entangled and integrated, and includes the CNT by a volume ratio of ≥80% or ≥99% in a nonrefined state. Further, granular or filmlike impurities consisting either of carbon other than that of the CNT or ash or of a mixture thereof are included in the inside by a volume ratio of ≤1%, or are stuck to the surface, and the volume ratio of the CNT as a whole reaches ≥80%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３５】
表１は、陰極に用いる炭素材料を変更した場合（炭素質の状況を変化した場合）のＣＮＴの採取状況を比較したものである。なお、アーク放電条件は、
（１）炭素陰極：直径３６ｍｍの棒状炭素材料で材質を種々変更（Ａ〜Ｇ）、
（２）陽極：直径１０ｍｍの棒状炭素陽極、
（３）放電用ガス：Ａｒガス（陽極放電発生部に供給）、
（４）雰囲気ガス：大気雰囲気である。
【００３６】
表１において、炭素材料Ａ、ＦおよびＧを陰極にした場合、ＣＮＴが高純度（高い採取率）で多く生成された。これらは全て材質が炭素質であり、製造時の熱処理温度が１０００℃から１５００℃のものであったから、かかる熱処理温度が好適であることが分かった。
また、炭素材料Ａ、ＦおよびＧの固有抵抗値は、それぞれ５９００μΩ・ｃｍ、４６００μΩ・ｃｍ、１１０００μΩ・ｃｍであったから、陰極炭素材料の固有抵抗値は、３５００μΩ・ｃｍより大きく、好ましくは４０００μΩ・ｃｍ以上であればよいことが分かる。
さらに、炭素材料Ａ、ＦおよびＧの熱伝導率は、それぞれ２３Ｗ／ｍＫ、３１Ｗ／ｍＫ、２０Ｗ／ｍＫであったから、陰極炭素材料の熱伝導率は、５２Ｗ／ｍＫより小さく、好ましくは４０Ｗ／ｍＫ以下であればよいことが分かる。
【００３７】
一方、炭素材料Ｂ、Ｃ、ＤおよびＥを陰極にした場合、ＣＮＴの純度（採取率）は低くまた収量（採取量）も少なかった。これらは全て材質が黒鉛質、あるいは黒鉛質と炭素質の混ざったものであった。
また、炭素材料Ｅの固有抵抗値は３５００μΩ・ｃｍであった。
さらに、陰極炭素材料Ｅの熱伝導率は５２Ｗ／ｍＫであった。
【００３８】
なお、上記の実験において、陽極炭素材料の材質を変更したが、ＣＮＴの収量および純度にはほとんど影響がなかったことからも、陰極炭素材料の材質がＣＮＴの収量および純度に大きく影響することが確認できた。
以上から、▲１▼製造時の熱処理温度を１０００℃から１５００℃にすることによって得られる炭素質からなる炭素材料、▲２▼電気抵抗値が４０００μΩ・ｃｍ以である炭素材料、または、▲３▼熱伝導率が４０Ｗ／ｍＫ以下となる炭素材料を陰極として用いることによって純度の高いＣＮＴを生成できる。
もっとも、たとえ製造時の熱処理温度が１０００℃から１５００℃の範囲内でなかったとしても、原料炭素質粉や結合材材質を変化させて電気抵抗値が４０００μΩ・ｃｍ以上、熱伝導率が４０Ｗ／ｍＫ以下となる炭素材料であればよいという知見が得られた。
【００３９】
図８および図９はＣＮＴ製造装置２（冷却陽極、図２参照）におけるアーク放電部の温度測定の結果を示すサーモビューア写真であって、それぞれ炭素材料Ｆおよび炭素材料Ｄにおけるものである。炭素材料Ｆ（黒鉛化の割合が低く、炭素質からなる）を用いた陰極のアーク放電部では高温領域が広くなっていることから、ＣＮＴ生成の重要なファクターとして、炭素陰極の放電部の温度が関係しているとの知見が得られた。
すなわち、炭素材料Ｆは前記熱処理温度が比較的低い炭素質であって、黒鉛化（結晶化）度が低いため、電気抵抗値（固有抵抗）が高く、熱伝導率の低いものである。
このため、陰極のアーク発生部（陰極点に同じ）は高い電流密度になり、大きな電気抵抗発熱によって高温度に加熱される。また、低い熱伝導率のため熱が逃げ難いから、陰極点近傍の狭い範囲に熱が籠もりさらに高温に加熱されることになる。このとき、陰極の温度がＣＮＴが生成され易い温度条件になるものと考えられる。
【００４０】
（電極材料２−触媒陰極）
陰極に用いられる電極材料は、前記炭素材料（炭素材料Ｆ等）そのものである場合に他に、該炭素材料にＣＮＴ合成の触媒作用を有するＮｉ等の触媒物質を混合した混合材料の場合がある。なお、触媒物質はＮｉの他に、Ｃｏ、Ｆｅ、Ｐｔ等の金属やＮｉ−Ｃｏ、Ｆｅ−Ｎｉ等の金属化合物の何れかであってもよい。また、該金属および金属化合物の２以上を混合したものであってもよい。
さらに、前記混合材料に代えて、前記炭素材料の表面に触媒物質の微粒子（たとえば、Ｎｉ微粒子）をバインダによって付着しても、触媒物質を化学的真空蒸着（ＣＶＤ）または物理的真空蒸着（イオンプレーティング）しても、触媒物質の微粒子と炭素粒子とバインダとを混合したもの塗布して付着しても、触媒物質の微粒子と炭素粒子とを混合してなるターゲットを用いて物理的真空蒸着してもよい。
【００４１】
すなわち、陰極を触媒物質の供給源としているから、前記生成領域の近傍（直流アークの陰極点の近傍）において、アーク熱によって少量の触媒物質が蒸発し、該触媒物質のナノレベルの超微粒子（混合した触媒物質の粒サイズよりも小さい）が当該生成領域に生成される。かかる超微粒子化された触媒物質は触媒として有効に作用するため、そのほとんどが触媒として機能し、必要量だけが蒸発するから、触媒物質の無駄な消費がなくなる。
また、同時に、蒸発した触媒物質が過大サイズの粒子に成長しないから、過大サイズの触媒物質がＣＮＴに混入する（一旦生成されたＣＮＴの上に堆積する）ことがなくなる。
【００４２】
さらに、直流アークは陽極から陰極へ向かって発生するので、陽極から触媒物質を供給した場合には直流アーク中で触媒粒子が大きく成長して、直流アークが乱れ易くなるもの、本発明のように陰極から触媒物質（陰極に混合した触媒物質の粒サイズが大きい場合であっも）を供給した場合には、直流アークの乱れが起こらずに安定した直流アーク放電が起こることになる。
【００４３】
（電極材料３−触媒陽極）
陽極に用いられる電極材料は、易黒鉛化炭素の粒子を加圧成型して焼結した炭素材料、または、前記炭素材料（炭素材料Ｆ等）そのものである場合に他に、該炭素材料にＣＮＴ合成の触媒作用を有するＮｉ等の触媒物質を混合した混合材料の場合がある。なお、触媒物質はＮｉの他に、Ｃｏ、Ｆｅ、Ｐｔ等の金属やＮｉ−Ｃｏ、Ｆｅ−Ｎｉ等の金属化合物の何れかであってもよい。また、該金属および金属化合物の２以上を混合したものであってもよい。
【００４４】
（電極材料４−金属陽極）
また、雰囲気ガスまたは炭素陰極から炭素蒸気ないし炭素イオンが供給される場合には、陽極を炭素材料に代えて、銅または銅合金等の金属材料によって形成することができる。このとき、陽極の消耗がほとんどないから、電極間距離の制御が容易になり安定しアーク放電が得られる。
さらに、金属陽極の場合、炭素蒸気もしくは炭素イオン供給量を他のパラメータと独立して制御できるため、余分な炭素原料を必要とせず、原料の削減が達成される。
【００４５】
すなわち、炭素陽極の場合、炭素陽極側から供給される炭素は、主にアーク熱によって加熱された炭素陽極が昇華したガス状炭素であると考えられ、この昇華量はアーク熱(アーク電流、電圧、雰囲気によって変動する)と炭素陽極の熱容量(形状によって変動する)により決まる従属パラメータである。また、このような昇華量はＣＮＴ生成に必要な量に比べ圧倒的に多いと考えられる。
【００４６】
［実施の形態３］
（ＣＮＴ製造方法１−固定中実陽極）
図１０は本発明の実施の形態３に係るＣＮＴの製造方法の実施例１（以下、ＣＮＴ製造方法１と称す）であって、ＣＮＴ製造装置１（固定中実陽極、図１参照）におけるアーク放電状況（一般放電）を示す模式図である。図１０における放電条件は以下である。
（１）陰極２０：板状炭素材料（抵抗値３５００μΩ・ｃｍ）
（２）陽極１０：棒状炭素材料
（３）放電用ガス：Ａｒガス（アーク放電発生部に供給）
（４）雰囲気ガス：大気雰囲気
【００４７】
このとき、アーク放電の発生する位置が大きく動き回り、陰極点の位置が陰極表面２１上で激しく不規則に移動する（図１０において、ある時間に発生したアークＡ１と、これとは異なる時間に発生したアークＡ２を重ねて図示している）。Ａ３は陰極ジェットであって、陰極の炭素が蒸発して一部の炭素原子が電離を起こしている部分である。
このようなアークの激しく不規則な移動は、大気圧下、アルゴンガス雰囲気中では特に顕著であるが、低圧力下のヘリウムガスや水素ガス雰囲気中でも、同様な動きが観察される。
【００４８】
図１１は、図１０の一般放電によりアークを短時間発生させた場合の陰極点を観察した結果を示す走査型電子顕微鏡（ＳＥＭ）写真である。図１１の（ａ）は陰極点の中心部とその周辺部を示すＳＥＭ写真、（ｂ）は陰極点中心部の拡大ＳＥＭ写真、（ｃ）は陰極点周辺部の拡大ＳＥＭ写真である。
これらのＳＥＭ写真から明らかなように、陰極点の中心部はＣＮＴが密集して生成されているのに対し、陰極点の周辺部においては、非晶質カーボン（アモルファスカーボン）の塊が堆積しているのみである。つまり、アークの陰極点ではＣＮＴが合成される条件が整っているのに対し、その周辺部は、ＣＮＴが合成されない条件となっていることが分かる。
これらの結果から、陰極点が激しく不規則に移動する一般のアーク放電形態では、陰極表面２１上でＣＮＴが合成される条件とＣＮＴが合成されない条件が交互に繰り返されると考えられる。
【００４９】
（ＣＮＴ製造方法２−冷却陽極）
本発明の実施の形態３に係るＣＮＴの製造方法の実施例２（以下、ＣＮＴ製造方法２と称す）は、ＣＮＴ製造装置２（冷却陽極、図２参照）を用いてＣＮＴを製造する方法であるが、前記ＣＮＴ製造方法１（固定中実陽極）に同じであるため、説明を省略する。
【００５０】
（ＣＮＴ製造方法３−予熱陰極）
図１２は本発明の実施の形態３に係るＣＮＴの製造方法の実施例３（以下、ＣＮＴ製造方法３と称す）であって、ＣＮＴ製造装置３（予熱陰極、図３参照）におけるアーク放電の陰極点中心部の拡大写真である。すなわち、以下の生成条件において、板状炭素陰極２０と棒状炭素陽極１０との距離を適当に設け、アーク放電用電源４０より電流を供給して１秒間アーク放電を行った。このときレーザ出力を変化させ板状炭素陰極２０の表面２１の加熱温度および生成したＣＮＴの量を観察した。
（１）陰極２０：板状炭素材料（抵抗値６００μΩ・ｃｍ）
（２）陽極１０：棒状炭素材料
（３）放電用ガス：Ａｒガス（アーク放電発生部に供給）
（４）雰囲気ガス：大気雰囲気
（５）陰極加熱手段６０：ＹＡＧレーザ（ビーム照射径が陰極表面２１の放電発生部の径とほぼ等しくなるように調整した）
（６）陽極冷却手段５０：水冷銅
【００５１】
図１２において、予熱をしなかった場合には、ＣＮＴは全く生成されなかった。５００℃に予熱をしたものは、ＣＮＴが一面に生成されているのが分かる。また、２０００℃に予熱をしたものは、ＣＮＴが一面に生成されると共に、ＣＮＴ繊維が長く成長しているのが分かる。
一方、２５００℃に予熱をしたものは、ＣＮＴが見られなかった。これは、２５００℃に予熱された上にアーク放電による発熱が加わるため、陰極表面２１が過熱され、ＣＮＴを生成する条件にならないこと、あるいは一旦生成したＣＮＴが昇華あるいは分解することが一因と推定される。
これより、陰極の予熱温度によってＣＮＴの生成は影響され、該予熱温度を５００℃〜２０００℃とすることが好適であることが分かる。
【００５２】
（ＣＮＴ製造方法４−ガス供給陽極）
図１３および図１４は、本発明の実施の形態３に係るＣＮＴの製造方法の実施例４（以下、ＣＮＴ製造方法４と称す）であって、ＣＮＴ製造装置４（ガス供給陽極、図４参照）におけるアーク放電状況を示す模式図および生成されたＣＮＴを示す走査型電子顕微鏡（ＳＥＭ）写真である。該ＣＮＴは陰極堆積物の中心部におけるものであって、高純度の多層ＣＮＴが合成されていることが分かる。なお、生成条件は以下である。
（１）陰極２０：板状炭素材料（抵抗値４６００μΩ・ｃｍ）
（２）筒状陽極１１：外径３６ｍｍで内径１０ｍｍの筒状の炭素材料
（３）放電用ガス：Ａｒガス（アーク放電発生部に供給）
（４）雰囲気：開放空間すなわち大気圧下で大気雰囲気
（５）放電用ガス：３％の水素を含むアルゴンガス、１０リットル／分の流量（筒状陽極１１の貫通孔１２から陰極２０に向けて吹き出し）
（６）アーク放電：電流５００Ａ、電圧３５Ｖ（アーク長約５ｍｍ）にて１分間アーク放電。
【００５３】
すなわち、筒状電極１１にから放電用ガスを吹き出すことによって、アークＡ４が放電用ガスの流路に沿って発生し、陰極点が放電用ガスの噴出口に常に対向する位置に発生するため、長時間に渡ってアークが安定する（陰極点が固定される）から、アーク放電の陰極点（陰極堆積物の中心部に同じ）に高純度のＣＮＴが合成されている。
【００５４】
これは、筒状電極１１の貫通孔１２の内面が放電用ガスと接しているため、ここに陽極点が安定して形成し易くなるためであると考えられる。
また、アルゴンなどの不活性ガスは、電子との衝突による電離能率が高く、アークＡ４を発生し易い空間を提供するから、筒状電極１１の貫通孔１２から陰極２０に向けて吹き出された放電用ガスがアークＡ４の発生経路を拘束するためと考えられる。
よって、筒状電極１１の貫通孔１２から陰極２０に向けて放電用ガスの送給を開始してからアークＡ４を発生させるようにすれば、アークＡ４の発生初期からアーク発生経路を拘束することができ、陰極点の不規則な移動を防止することができるから、かかる陰極点において形成されたＣＮＴの生成条件が維持され、ここに高純度のＣＮＴが堆積することになる。
【００５５】
なお、筒状電極１１の貫通孔１２から送給する放電用ガスは、▲１▼純アルゴン、もしくは、▲２▼２０％程度以下の水素ガスを混入したアルゴンガス、▲３▼２０％程度以下の水素ガスやヘリウムガスを混入したアルゴンガスであってもよい。
特にアルゴンに水素ガスを数％〜数十％混ぜると、アークの安定性を損なうことなく、ＣＮＴの収量を増加することができた。これは、水素ガスにはアークを収束させる効果があり、アーク温度の上昇または陰極表面の電流密度が上昇し、ＣＮＴが生成されやすい条件となるためと考えられる。
【００５６】
図１５は、ＣＮＴ製造装置４（ガス供給陽極、図４参照）における、筒状電極の貫通孔の断面積と供給する（吹き出すに同じ）放電用ガスの流量とアーク発生形態との関係を示す実験結果のグラフである。図１５において、放電用ガス（純アルゴンもしくは２０％程度以下の水素ガスやヘリウムガスを混入したアルゴンガス）の流量が貫通孔１２の断面積１ｍｍ² 当り１０ｍl/分よりも少なすぎると、プラズマガスとして十分に機能せず、また流量が孔１１ａの断面積１ｍｍ² 当り４００ｍl/分よりも多すぎると、電極周辺部までプラズマガスの濃度が増加し、中央部だけでなく、周辺部でもアーク放電が起こり易い条件となり、アークを集中させることができなくなる。
すなわち、放電用ガスの流量を、貫通孔１２の断面積１ｍｍ² 当り１０〜４００ｍl/分とすることにより、プラズマガスとして機能させつつ、筒状陽極１１の中央部のみに周辺部に比べアーク放電し易い条件をつくり出すことができる。よって、陰極点が固定されるから純度の高いＣＮＴを収率良く回収することが可能になる。
【００５７】
図１６は、ＣＮＴ製造装置４（ガス供給陽極、図４参照）における、筒状電極の貫通孔の断面積と供給する（吹き出すに同じ）放電用ガスに触媒粉末を混入される状況を説明する模式図である。なお、図４と同じ部分にはこれと同じ符号を付し、一部の説明を省略する。
すなわち、筒状陽極１１の貫通孔１２と触媒混入容器７１を連通している。そして、触媒となる金属粉末または金属化合物粉末Ｍ１（以下、触媒物質Ｍ１と称す）を収容した触媒混入容器７１内において、放電用ガスと触媒物質Ｍ１とを混合して、陰極２０に向けて吹き付けている。すなわち、放電用ガスに乗せて触媒物質Ｍ１をアーク発生部に供給している。
【００５８】
このとき、アーク放電による高温下で、放電ガスの電離度が上がり、導電性が周辺部に比し大きくなるから、筒状電極１１の陽極点が安定して形成され、放電用ガスの経路に沿ってアークＡ４が発生する拘束アーク形態（陰極点の固定に同じ）となる。さらに、放電用ガスに混入された触媒物質Ｍ１がアーク熱により超微粒化し、それが作用して単層のＣＮＴが生成される。つまり、固定された陰極点およびその周辺部の陰極堆積物から高純度の単層ＣＮＴを回収することができる。
【００５９】
（ＣＮＴ製造方法５−ノズル付き陽極）
なお、本発明の実施の形態３に係るＣＮＴの製造方法の実施例５（以下、ＣＮＴ製造方法５と称す）は、ＣＮＴ製造装置（添設した放電用ガスノズルから放電用ガスを吹き出している、図５参照）によってＣＮＴを製造するものである。これにおいても、前記ＣＮＴ製造方法４（筒状電極の貫通孔から放電用ガスを吹き出している）と同様に、陰極点の固定が観察され、固定された陰極点およびその周辺部の陰極堆積物から高純度の単層ＣＮＴが回収されている。
生成状況は前記ＣＮＴ製造方法４（ガス供給陽極）に同じであるため説明を省略する。
【００６０】
（ＣＮＴ製造方法６−移動するガス供給陽極）
図１７は本発明の実施の形態３に係るＣＮＴの製造方法の実施例６（以下、ＣＮＴ製造方法６と称す）であって、ＣＮＴ製造装置６（移動陽極、図４および図６参照）において生成されたＣＮＴを示す模式図である。なお、生成条件は以下である。
（１）陰極２０：板状炭素材料（抵抗値３５００μΩ・ｃｍ）
（２）筒状陽極１１：外径１０ｍｍで内径４ｍｍの筒状炭素材料
（３）雰囲気：開放空間すなわち大気圧下で大気雰囲気
（４）放電用ガス：３％の水素を含むアルゴンガス、１リットル／分の流量（筒状陽極１１の貫通孔１２から陰極２０に向けて吹き出し）
（５）アーク放電：電流１００Ａ、電圧２０Ｖ（アーク長約１ｍｍ）にて１分間アーク放電。
（６）陽極移動：１０ｃｍ／分
【００６１】
すなわち、筒状電極１１を一方向に移動させながらアーク放電を行った結果、陰極表面２１に帯状に付着した陰極体積物が生成された。該陰極体積物は中央部（アークＡ４の中心部（陰極点）が走査した経路に相当）が帯状に自然剥離するテープ状の物質Ｃ２１と、その両側で陰極表面２１に付着した付着物質Ｔ２３によって構成されている。
このテープ状物質Ｃ２１を走査型電子顕微鏡（ＳＥＭ）および透過型電子顕微鏡（ＴＥＭ）により観察したところ高純度のＣＮＴの集合体で構成されていることが判明した（以下、高純度ＣＮＴテープまたはＣＮＴテープと称す）。また、付着物質Ｔ２３はアモルファスカーボンであった。
【００６２】
図１８は製造方法６（移動するガス供給陽極）における高純度ＣＮＴテープの生成機構（生成メカニズム）を推定した模式図である。ＣＮＴの生成機構は静止アーク（ＣＮＴ製造方法４−ガス供給陽極、図１６参照）の場合と同様である。すなわち、アークＡ４の中心部にＣＮＴが生成され、その周辺部にアモルファスカーボンが堆積する。
【００６３】
このため、陽極を移動する場合（以下、移動アークと称する場合がある）、アークＡ４の移動に伴ってＣＮＴが生成され易い条件も一緒に移動する。このため、アークＡ４が近づくとアークＡ４の周辺部にアモルファスカーボンＴ２３が堆積し、ここに、アークＡ４が到達すると、既に堆積しているアモルファスカーボンＴ２３の上にＣＮＴが生成され易い条件（アークＡ４の中心部に同じ）ができるから、この上にＣＮＴが生成される。さらに、アークＡ４の中心部が去っていくと、生成されたＣＮＴの位置においてＣＮＴが生成され易い条件が崩れるため、生成したＣＮＴの上にアモルファスカーボンＴ２３が堆積することになる。
よって、ＣＮＴは上下左右をアモルファスカーボンＴ２３に包囲されたテープ状に形成される（図１８の上段（ａ）参照）。
【００６４】
しかし、アークＡ４が過ぎ去った後、上面のアモルファスカーボンＴ２３は高温の状態で大気と触れ合うため、酸化・燃焼して一部が焼失する（図１８の中段）（ｂ））。
【００６５】
さらに、陰極堆積物が低温になると、ＣＮＴテープＣ２１とアモルファスカーボンＴ２３との熱膨張率の相違により、ＣＮＴテープＣ２１がテープ状に剥離する現象を起こす（図１８の下段（ｃ））ものと考えられる。
すなわち、筒状電極１１のアーク放電による陰極点の固定によって高純度のＣＮＴが生成され、さらに、該筒状電極１１を移動することによって高純度ＣＮＴをテープ状に形成でき、さらに、該ＣＮＴテープが自然剥離するから、かかる高純度ＣＮＴテープを容易に高い収率で回収することが可能になる。
【００６６】
（ＣＮＴ製造方法６の２−移動するガス供給陽極と加熱陰極）
図１９はＣＮＴ製造装置６（移動するガス供給陽極）に加熱陰極を採用して生成されたＣＮＴの製造方法６の２によって生成された高純度ＣＮＴテープを示す電子顕微鏡写真である。なお、生成条件は以下のとおりである。
（１）炭素陰極１：平板状炭素材料
（２）陽極３：棒状炭素材料
（３）放電用ガス：Ａｒガス（陽極放電発生部に供給）
（４）雰囲気ガス：大気雰囲気
（５）陰極加熱手段：高周波誘導加熱装置（炭素陰極との間隔：４ｍｍ）
（６）陽極冷却手段：水冷銅
（７）台車１９移動速度：１０ｃｍ／ｍｉｎ
【００６７】
上記の条件で高周波誘導加熱装置の発振周波数を１０ｋＨｚとして加熱を行うと、高周波誘導加熱のみで陰極温度が８００℃に上昇した。この状態で放電用ガス供給装置よりＡｒガスを放電空間に噴射し、陽極と陰極の間にアーク放電を発生させると、高密度・高純度のＣＮＴテープが生成される。
なお、大気中放電時間を５分としたが、陽極を冷却しない場合には消耗が激しく、２分以上の連続放電は不可能であった。これに対して、陽極を水冷したものは放電開始直後に多少消耗するが、その後消耗量が低くなり長時間放電が可能になった。
【００６８】
陽極を冷却した場合は冷却をしない場合に比べ、回収したＣＮＴテープの表面に付着した不純物の量が減少しているから、陰極堆積物中の炭素不純物の多くは陽極からの飛来物であることが推定される。よって、陽極を冷却することにより必要以上の陽極消耗を抑え、陰極堆積物中の炭素不純物となる陽極からの飛散物の堆積を抑制することが可能となるだけでなく、陽極の長寿命化が図れることが実証できた。
【００６９】
（ＣＮＴ製造方法７−回転陰極）
図２０は本発明の実施の形態３に係るＣＮＴの製造方法の実施例７（以下、ＣＮＴ製造方法７と称す）であって、ＣＮＴ製造装置７（回転陰極、図７参照）におけるアーク放電状況を示す模式図である。図２０における放電条件は以下である。
（１）回転陰極２３：直径３５ｍｍの円柱状炭素材料、回転速度は１．５回転／分
（２）筒状陽極１１：外径１０ｍｍ、内径４ｍｍの中空炭素電極、移動速度は３５ｍｍ／分
（３）放電用ガス：純アルゴンガス、流量は１リットル／分
（４）雰囲気ガス：大気圧下・大気雰囲気
（５）放電条件：電流１００Ａ、電圧２０Ｖ（アーク長約１ｍｍ）
すなわち、回転陰極２３を回転させるとともに、筒状電極１１を回転陰極２３の軸方向に直線的に移動させて回転陰極上に螺旋を描く形で陰極点を移動させた。
【００７０】
その結果、幅２〜３ｍｍ程度、厚さ１００ミクロン程度の帯状箔である高純度ＣＮＴテープが生成された。このＣＮＴテープの幅および厚さは、電極の形状、サイズおよび生成条件により変化させることが可能である。なお、本発明において、精製処理（加熱等）を施していないものを「非精製状態のＣＮＴ」と称す。
【００７１】
図２１および図２２にそれぞれ生成された高純度ＣＮＴテープの外観写真およびＳＥＭ写真を示す。テープ表面には１０ｎｍ程度の球状のアモルファスカーボンが付着しているが、内部は高純度のＣＮＴの集合体で構成されている。なお、この程度の量のアモルファスカーボンは酸化雰囲気中の熱処理（別工程）により容易に除去することができる。
【００７２】
（ＣＮＴ製造方法７の２−移動するガス供給陽極と冷却ガス吹き付け）
図２３は、ＣＮＴ製造装置７（回転陰極）に冷却ガス吹き付け手段を配置したＣＮＴ製造方法７の２におけるアーク放電状況を示す模式図である。図２３における放電条件は前記図２０に示すものに同じである。なお、図２０と同じ部分にはこれと同じ符号を付し、一部の説明を省略する。
すなわち、アークＡ４の陰極点の軌跡上に生成されている高純度ＣＮＴテープＣ２１に、ガスノズル５１から冷却用ガスを吹き付けるようにしたものである。
【００７３】
ＣＮＴテープＣ２１の生成後に冷却用ガスを吹き付けて冷却を促進することにより、剥離を助長させている。冷却用ガスは限定するものではなく、冷却効果をそ奏するものなら空気、窒素等、何でも使用可能である。
ＣＮＴテープＣ２１は回転陰極２３上に薄い膜状（帯状の箔状）に生成されているので、冷却用ガスを吹き付けることによって急速に冷却されると、周囲のアモルファスカーボンＴ２３および回転陰極２３との間に熱応力が働いて剥離が促進されるものである。
【００７４】
なお、冷却用ガスに含まれた酸素、または冷却用ガスに巻き込まれた空気によって、ＣＮＴテープＣ２１に付着しているアモルファスカーボン等（多結晶黒鉛および非晶質炭素の箔状片や粒子）の酸化・燃焼が促進されるため、ＣＮＴテープＣ２１の純度が上がるとともに、回転陰極２３の表面との付着力が弱まって剥離がさらに容易になる。
【００７５】
また、該付着力は、陰極材料の表面の表面粗さ（たとえば、算術平均粗さ（Ra））によっても変動する。すなわち、陰極材料の表面粗さが粗い場合、該付着力が高まるため、たとえば、回転陰極２３の上面を算術平均粗さ（Ra）が３．２μｍ以下にしておけば、付着力が弱まり自然剥離が進むから、ＣＮＴテープＣ２１の回収がいたって容易になる。
【００７６】
（ＣＮＴ製造方法７の３−移動するガス供給陽極と陰極加熱）
図２４は、ＣＮＴ製造装置７（回転陰極、図２０参照）に陰極加熱手段を配置したＣＮＴ製造方法７の３におけるアーク放電状況を示す模式図である。図２４における放電条件は前記図２０に示すものに同じである。なお、図２０と同じ部分にはこれと同じ符号を付し、一部の説明を省略する。
すなわち、アークＡ４の陰極点もしくは回転陰極２３上のアークＡ４の軌道におけるアークの進行方向前方部分を、レーザ発振器６０からのレーザ光線によって加熱しながらアーク放電を行うようにしたものである。
【００７７】
このとき、陰極点の温度は予熱がない場合に比べ高い温度になり、かつ純度の高いＣＮＴテープＣ２１を回収することができた。
なお、レーザ発振器６０に代えて、通電による抵抗発熱によって陰極全体を予熱・加熱したり、周囲から輻射によって回転陰極の表面を予熱・加熱したりしてもよい。
以上、実施の形態３において、ＣＮＴ製造方法を個別に説明しているが、本発明はこれに限定するものではなく、かかるＣＮＴ製造方法の何れか同士を適宜組み合わせて実施してもよい。
【００７８】
［実施の形態４］
図２５および図２６は本発明の実施の形態４に係るアーク放電によって生成されたＣＮＴを示す電子顕微鏡写真であって、図２５の（ａ）は回収されたＣＮＴの小片の外観写真、図２５（ｂ）、図２６の（ｃ）および（ｄ）はその表面（非精製状態）を電子顕微鏡で観察したものである。
なお、ＣＮＴの生成方法は前記ＣＮＴ製造方法４（ガス供給陽極）によるものであって、その放電条件は以下である。
（１）陰極２０：直径２０ｍｍ、厚さ５ｍｍの板状炭素材料（抵抗値６００μΩ・ｃｍ）
（２）筒状陽極１１：直径１１ｍｍ、内径４ｍｍの炭素材料
（３）放電用ガス：Ａｒガス、０．５〜５リットル／分
（４）雰囲気ガス：大気雰囲気
（５）放電条件：電流１００Ａ、電圧２０Ｖ、放電時間０．１〜１秒
【００７９】
このとき、陰極堆積物は円状に堆積したＣＮＴと、その周囲に円環状に堆積したアモルファスカーボンからなり、該ＣＮＴの堆積した直径は４ｍｍであって、アーク放電の放電発生部の大きさとほぼ一致している。なお、上記条件で電極を相対移動した場合には、幅４ｍｍの帯状のＣＮＴテープが得られる（以下に、別途説明する）。
堆積したＣＮＴを電子顕微鏡によって観察すると、表面が滑らかな相当の長さを有する長い繊維（以下、ＣＮＴ繊維と称す）がランダムに複雑に絡み合って綿状になったものである（以下、ＣＮＴ集合体と称す）。
【００８０】
（ＣＮＴ繊維）
ＣＮＴ集合体を構成するＣＮＴ繊維は、長さは１０μｍ以上のものが大半を占め、中には２０μｍを越すものも見られた。より詳細な観察を行うと５０μｍ以上や１００μｍに達するものまで、数は少ないが観察される。
各々のＣＮＴ繊維に注目すると、端部付近では直線状の形状を有しているが、連続的な円弧状を描くものが多く見受けられ、曲率半径が１〜１０μｍのものが多い。無論、直線部すなわち曲率半径無限大の部分も存在し、一方、折れ曲がった状態の曲率半径２００ｎｍ程度のものも観察される。
【００８１】
また、ＣＮＴ繊維は途中で枝分かれしておらず、また、表面に露出した端部が直線状に延びていることから、アーク放電法特有の結晶性の高いＣＮＴ繊維で構成されていることが確認される。さらに、ＣＮＴ繊維同士は、絡み合った個所において緩い弧を描いていることから弾性変形を起こしている状況が観察されるため、かかるＣＮＴ繊維は可撓性を有していると推定される。
【００８２】
図２７は、図２５に示すＣＮＴ繊維の太さの測定結果を示す分布図である。図２７より、直径約５〜１０ｎｍのものが略６０％を占め、約１５ｎｍ以下のものが略９０％を占めている。
なお、このように長尺のＣＮＴ繊維（後記するように結晶性が高い）は、アーク放電を用いて生成することができるものである。一方、気相成長法（ＣＶＤ法）やレーザアブレーション法では、このように結晶性が高く長尺のＣＮＴ繊維を生成することができず、またかかる長尺の繊維が絡まった綿状の集合体を得ることもできない。
【００８３】
（結晶性）
従来は、グラフェン筒の構造が良くて一枚一枚のグラフェン筒が明確に認識できるＣＮＴで長いものを生成することは困難であった。グラフェン筒の構造が良くて一枚一枚のグラフェン筒が明確に認識できることを、結晶性が良いという言葉で一般的に言い表されている。
結晶性が良いＣＮＴは、一般にアーク放電法により生成されると言われているが、従来のアーク放電法では、長いものでも１μｍ程度のＣＮＴ繊維しか生成できなかった。
【００８４】
一方、気相成長法（ＣＶＤ法）では、長いＣＮＴが生成できるとされているが、長いものはその直径も５０ｎｍ以上と太いものが多く結晶性も悪いものであった。このような結晶性の悪いＣＮＴは熱処理によって、結晶性の良いものに改質することができるが、改質のためには３０００℃近い高温度の熱処理が必要であるばかりではなく、熱処理を行ってもＣＮＴの長さ方向に、ある一定の確率で発生する層状欠陥を防止することは難しかった。また、熱処理過程において、ＣＮＴの長さが短くなってしまい、結晶性が良く、かつ１０μｍを超える程の長いＣＮＴを得ることは困難であった。
【００８５】
図２８は本発明の実施の形態４に係るアーク放電によって生成されたＣＮＴの結晶性を説明する模式図である。図２８の（ａ）は、ＣＮＴ側壁部の六角網面の状態を模式的に表したものであって、アーク法によるＣＮＴの状態を示している。網平面が繊維軸に並行で長く、グラフェン筒を明確に形成しており、その積層間隔も均等なものになっている。
一方、図２８の（ｂ）はＣＶＤ法で生成されたＣＮＴの構造であって、小さな網面が断続的に連なった状態であり、繊維軸にほぼ平行に配向しているものの、その面間隔もまちまちなものとなっている。
【００８６】
本来、結晶とは、３次元的な原子の配置に規則性がなければならず、網面の積層方向にも所定の規則的な関係がなければならないが、一般にＣＶＤ法によって生成された多層ＣＮＴにはその関係はなく、いわゆる乱層構造となっている。
よって、厳密な意味で、黒鉛結晶とは異なるが、図３の（ａ）のように網平面が繊維軸に並行で長く、その積層間隔も均等なものをＣＮＴの結晶性が良いという言葉で表している。このように、網平面が繊維軸に並行で長く繋がっているという構造が、強度および熱伝導性や導電性に優れた特性を示す要因となっている。
【００８７】
さらに、図２８の（ｃ）および（ｄ）は、ＣＶＤ法によって生成されたるＣＮＴを熱処理した際に発生し易い層状欠陥を表している。（ｃ）は長さ方向途中における層の欠如を、（ｄ）は長さ方向途中における層の食い違いを示している。
【００８８】
本発明に係るＣＮＴは、結晶性が良く、長尺の繊維状で、さらに純度が高いため、利用十分な強度を持って形成することができる。すなわち、薄く、かつミリメートルサイズの広がりを持った膜状物質として形成することができ、取り扱いも容易で、電子放出源やセンサまたは機能性分離膜など広い用途に、容易に使用できるようになる。
【００８９】
一方、従来は結晶性が良く、長いＣＮＴがなかったため、これを樹脂や金属などに混合して使用していたから、多くのＣＮＴを用いなければならなかった。また、ミリメートルサイズの広がりを持った膜状物質として形成することが困難であって、長いＣＮＴと同量混入したとしても導電性や強度および熱伝導性など多くの点で特性が劣っていた。
【００９０】
（ＣＮＴ集合体の疎密領域）
ＣＮＴ集合体の中には、疎に集合した領域と、密に集合した領域が観察され、密に集合した部分は他の部分に対して開放空間側に凸になっている（盛り上がっている）。
また、この密になっている部分は長いＣＮＴが束上に寄り添っており、先端に近づくほどＣＮＴの本数が徐々に減り、先端では１０本以下、ほとんどは５本以下、中には一本のＣＮＴで終わっているものも観察される。
この密に集合した領域の間隔は、２〜４０μｍの範囲にあるが、この間隔は生成条件により異なり、本実施例の場合５〜２０μｍの間隔で均一に分布している。これを視野２μｍの直方体で見た場合、体積密度（単位体積当りでＣＮＴ繊維が占める体積の割合であって嵩密度に同じ、なお、嵩比重との混同を避けるため体積密度と称す）１／５以上の領域さらに詳しく観察すると１／２以上の密の領域が存在する。
一方、疎に集合した領域は、視野２μｍの直方体で見た場合、体積密度１／１００以下さらに詳しく観察すると体積密度１／５００以下、より詳細に観察すると数は少ないが体積密度１／１０００以下の領域が観察された。
【００９１】
（不純物）
ＣＮＴ集合体の表面を観察すると、粒径の小さい不純物あるいは膜状の不純物が付着していることが観察される。
ある範囲における粒状の不純物の直径は１００ｎｍ以下、観察した限りではほとんどが粒径５０ｎｍ以下のものであり、これらの占める面積は視野全体の１％以下である（すなわち、ＣＮＴの表面における純度は９９％を越える）。
なお、後記の手法により内部を露出させて観察したところ、前記不純物は見られなかった。したがって、該範囲におけるＣＮＴ集合体の全体の純度は極めて高く略１００％に近いものである。
【００９２】
また、他の範囲において、膜状の不純物が表面の２０％以上、中には７０％以上を占めるものがある。該不純物は、ほぼ炭素からなる膜状であって、この膜厚は厚いところで１００ｎｍ〜数μｍ、重量換算で陰極堆積物の全体に対し多くとも２０％以下の量であった。よって、ＣＮＴ集合体の堆積物に占める割合（純度）は少なくとも８０％以上であると言える。
【００９３】
（ＣＮＴテープ）
図２９は本発明の実施の形態４に係るアーク放電によって生成されたＣＮＴを示す透過電子顕微鏡写真であって、その表面（非精製状態）を透過電子顕微鏡で観察したものである。なお、ＣＮＴの生成方法は前記ＣＮＴ製造方法７（回転陰極）によるものであって、その放電条件は以下である。
（１）回転陰極２３：直径３６ｍｍの円柱炭素材料、０．５〜３回転／分
（２）筒状陽極１１：直径１０ｍｍ、内径４ｍｍの炭素材料、１０〜５０ｍｍ／分で陰極の軸方向に移動
（３）放電用ガス：Ａｒガス、０．５〜５リットル／分
（４）雰囲気ガス：大気雰囲気
（５）放電条件：電流１００Ａ、電圧２０Ｖ
【００９４】
なお、陽極は水冷銅電極でもよい。陰極は抵抗率の大きいもの、好ましくは２０００μΩ・ｃｍ以上、さらに好ましくは４０００μΩ・ｃｍ以上がＣＮＴ集合体の生成に適している。また、抵抗率が低い場合には、陰極放電発生部を予熱（好ましくは５００〜２０００℃の範囲）しながら、アーク放電を行うことにより、同様のＣＮＴ集合体を得ることが可能である。
これによってテープ状のＣＮＴ集合体が回収され、非精製状態で幅１〜１０ｍｍ、厚さ１０〜５００μｍ、長さは生成条件、製造装置によっても左右されるが、所望の長さのものを容易に回収することができる。なお、アーク放電によって陰極表面のアーク放電発生部は変質する。
【００９５】
（目視形状）
図２９において、ＣＮＴ集合体を構成するＣＮＴ繊維は３層以上のグラフェンシートを有する多層ＣＮＴ（ＭＷＣＮＴ）がほとんどを占めている。また、あるＣＮＴ繊維において、一方のＣＮＴ繊維が接触している位置と他方のＣＮＴ繊維が接触している位置との距離（接触間隔）は様々であるが、少なくとも５μｍ以上、他さらに詳しく観察すると、この距離が１０μｍ以上のものも見られ、中には、２０μｍ以上のものも数少ないが表面付近に観察される。
アークが通過してから数秒〜数分が経過すると、回転陰極の表面から箔状の集合体が自然に剥離してくる場合があり、自然剥離しない場合においても強制冷却等によって容易に剥すことが可能である。よって、任意の長さを有したＣＮＴテープを得ることができる。このＣＮＴテープを、所定の長さもしくは任意の大きさに分割することにより、各種利用が可能なＣＮＴ集合体を得ることができる。
【００９６】
（嵩比重）
さらに、厚さ５０μｍで各辺３ｍｍ角の正方形状シートにしたＣＮＴ集合体の質量はおよそ２０μｇであるから、嵩比重は４４ｍｇ／ｃｍ³である。
なお、後記する透過顕微鏡観察からも明らかなように、多層ＣＮＴの繊維は内部に空間を有する管状（文字通りのチューブ）であるものの、内部の空間の割合は極めて少ない。すなわち、特定の多層ＣＮＴ繊維を観察すると、これを形成するグラフェンシートを合計した体積が、該チューブの体積（最外層のチューブの体積に同じ）に対して略７０〜９０％であって、平均すると略８０％である。
したがって、多層ＣＮＴ繊維の体積密度を０．８とすると、黒鉛の比重が２．２５ｇ／ｃｍ³であることから、多層ＣＮＴ繊維の比重は、１．８ｇ／ｃｍ³となる。
すなわち、１ｃｍ³の体積中に多層ＣＮＴ繊維が中実に詰まった場合１．８ｇであるのに対し、実際のＣＮＴ集合体は４４ｍｇであるから、体積密度は、４４ｍｇ／１．８ｇ＝（１／４１）となる。
ただし、この嵩比重はバラツキが大きく、また、外力により圧縮することで、より密にすることが可能である。
【００９７】
（電子放出特性）
また、外力により、嵩比重を変化させた場合の電子放出特性を求めたところ、嵩比重が高くなるに従い電子放出特性が悪くなることが判明した。
たとえば、５０μＡ／ｍｍ²の平均電子放出密度を得るために、
▲１▼嵩比重が３５ｍｇ／ｃｍ³（体積密度１／５１に相当）の場合には６〜７ｋＶ／ｍｍの平均電界強度を得る電圧を印加するだけでよいのに対し、
▲２▼嵩比重が０．１８ｇ／ｃｍ³（体積密度１／１０に相当）の場合には８ｋＶ／ｍｍ程度の平均電界強度を得る電圧を印加する必要が生じ、
▲３▼さらに、嵩比重が０．９ｇ／ｃｍ³（体積密度１／２に相当）の場合は、１５ｋＶ／ｍｍの平均電界強度を得る電圧を印加する必要がある。
【００９８】
これは、体積密度を高めることにより表面が巨視的に平滑化し、局所的電界強度が低下しているものと考えられる。
すなわち、体積密度１／１０以下（嵩比重は０．１８ｇ／ｃｍ³以下）であれば、電子放出源として十分な機能を発揮することが判明した。
一方、一般のアーク放電法にて生成されたＣＮＴを精製して純度を限りなく高めたものを塗布した場合、５０μＡ／ｍｍ²の平均電子放出密度を得るために、７〜８ｋＶ／ｍｍ程度の平均電界強度を得る電圧を印加することから、本発明に係るＣＮＴ集合体は非常に良い電子放出特性であると言える。
【００９９】
さらに、回収したＣＮＴテープの電子放出源特性を調査した中で、低い印加電圧にて高い平均電流放出密度を得るものがいくつか見られたが、このＣＮＴ集合体の構成ＣＮＴの径を調べたところ、直径４〜１５ｎｍのＣＮＴが全体の５０〜８０％を占めていた。
よって、本発明に係るＣＮＴ集合体を電子放出源として用いる場合、基板上に生成したままＣＮＴ集合体（不純物の除去する精製処理を不要とする）を接着するだけでよい。
【０１００】
［実施の形態５］
（ＣＮＴの引っ張り加工）
図３０は本発明の実施の形態５に係るアーク放電により製造されたＣＮＴの引っ張り加工状況を説明する模式図である。図３０において、幅３ｍｍで長さ１０ｍｍのＣＮＴテープ（図３０の（ａ）参照）を、長手方向に引っ張ると、途中で破断して、破断面にＣＮＴ繊維の先端が毛羽立ったように露出する（以下、破断後の一方を加工片と称す、図３０の（ｂ）参照）。
よって、該加工片を基板Ｅ１に貼り付ける（図３０の（ｃ）参照）、または複数の加工片を並べて基板Ｅ１に貼り付ける（図３０の（ｄ）参照）ことで、良好な電子放出源を得ることができる。
【０１０１】
（ＣＮＴの引っ張り破断部の状況）
図３１は本発明の実施の形態５に係るアーク放電により製造されたＣＮＴを引っ張り加工した後の側面を示す電子顕微鏡写真である。図３１は破断面の近くを側面から観察した電子顕微鏡写真であって、破断面と垂直に近い角度で、ＣＮＴ繊維が開放空間に伸びている。この部分をさらに観察すると、ＣＮＴ繊維は端部を有しているものがほとんどであった（両端がＣＮＴ集合体内に侵入して途中が破断面に現れたループ状のものが少ないに同じ）。
なお、ここで言う端部とは、ＣＮＴ繊維が破断した端部、およびＣＮＴ繊維特有の炭素原子で閉じた面（本来、生成状態において端部を有するＣＮＴ繊維の端部）の両方を意味する。
かかる、引っ張り破断面にのみ着目した小範囲の電子放出特性は、５０μＡ／ｍｍ²の平均電流密度を得るために、５〜６ｋＶ／ｍｍの平均電界強度でよく、極めて良好な値を示している。
【０１０２】
（ＣＮＴの引き剥がし加工）
図３２は本発明の実施の形態５に係るアーク放電により製造されたＣＮＴの引き剥がし加工状況を説明する模式図である。図３２の（ａ）において、ＣＮＴテープＣ２１の裏面（陰極側）を電子放出源基板Ｅ１に、表面（陽極側）Ｂ２を他の電子放出源基板Ｅ２貼り付けた（それぞれ、接着剤Ｂ１、Ｂ２による）。
そして、図３２の（ｂ）において、電子放出源基板Ｅ１、Ｅ２を引き剥がしたところ、ＣＮＴテープＣ２１は厚さ方向の中間で引き剥がされた形となった。すなわち、電子放出源基板Ｅ１、Ｅ２のそれぞれにＣＮＴテープＣ２１が接着したまま、ＣＮＴ集合体の内部が新たに表面に現れたことになる。
【０１０３】
（引き剥がし面）
図３３は本発明の実施の形態５に係るアーク放電により製造されたＣＮＴの加工後の表面を示す電子顕微鏡写真である。図３３において、引き剥がした後の表面（引き剥がし前はＣＮＴ集合体の内部であった）は、製造ままのＣＮＴテープの表面に見られた不純物の量が激減し、さらに、ＣＮＴの端部が多く露出している。
【０１０４】
（引き剥がし面の電子放出特性）
この引き剥がしたＣＮＴ集合体を用いた電子放出源の電子放出特性を調べたところ、５０μＡ／ｍｍ²の平均電流密度を得るために、５〜６ｋＶ／ｍｍの平均電界強度でよく、引き剥がす前（非精製状態）のＣＮＴ集合体を用いた場合に比べ、電子放出特性が向上していることが分った。
この理由は定かでないが、（イ）不純物が極めて少ないこと、（ロ）多くのＣＮＴ繊維の端部が表面に毛羽立って露出していること、（ハ）さらにはいくつかのＣＮＴ繊維がＣＮＴ集合体の表面付近で破断し、一般的には閉じているとされているＣＮＴ繊維ののグラフェンシートが千切られ、グラフェンシートの端部が露出していることによるもの、と考えられる。
【０１０５】
（ＣＮＴ集合体の加工片の電子放出特性）
本発明に係るＣＮＴ集合体の電子放出特性は、５０μＡ／ｍｍ²の平均電子放出密度を得るために、６〜８ｋＶ／ｍｍ程度の平均電界強度を得る電圧を印加するだけで済み、特に、体積密度１／５０の場合には、６〜７ｋＶ／ｍｍの平均電界強度を得る電圧を印加するだけでよい。
一方、一般のアーク放電法にて生成されたＣＮＴを精製して、その純度を限りなく高めたものを塗布した場合であっても、７ｋＶ／ｍｍの平均電界強度を得る電圧を印加する必要があることから、本発明に係るＣＮＴ集合体の電子放出特性は極めて優れていると言える。
よって、本発明に係るＣＮＴ集合体を電子放出源として用いる場合、基板上に非精製状態のＣＮＴ集合体（不純物の除去する精製処理を不要とする）を接着するだけでよい。
【０１０６】
［実施の形態６］
以下、本発明の実施の形態６に係るアーク放電により製造されたＣＮＴの利用について説明する。
（面積）
ＣＮＴの実使用を考えた場合は、必要に応じた面積を有するＣＮＴが必要である。従来技術では大きな面積を持つ一体化したＣＮＴ集合体を得るためには、気相成長法などの化学プロセスによるか、もしくは、生成法は問わないがＣＮＴを粉体として、塗布あるいは散布することで面を構成するしかなかった。
【０１０７】
しかしながら、気相成長法（ＣＶＤ法）に代表される化学プロセスでは、たとえば平面基板の上でＣＮＴを成長させると、成長速度を局所的に変化させることは困難であり、凹凸はほとんど生じない。加えて、気相成長法により作られたＣＮＴは結晶性の低さから、無秩序に曲がりくねったものが生成されるため、表面にほとんど凹凸のない（非常に平滑）ＣＮＴ集合体が得ることになる（なお、後記するように、ＣＶＤ法によって生成されたＣＮＴ繊維の表面は平滑でなく、本発明に係るＣＮＴ繊維は表面が平滑で直線状である）。
【０１０８】
アーク放電法や気相成長法にて作られた粉体状のＣＮＴを平板上に塗布あるいは散布した場合、やはり均一に散布され易く、少なくとも密な集合と疎な集合を狭い間隔、たとえば２０μｍ毎に混在させることができない。
これに対し、本発明に係る集合体ＣＮＴは、０．１ｍｍ角の正方形（たとえば電子放出源として必要最小限と思われる領域）はもちろんのこと、直径４ｍｍの円状、または幅５ｍｍで長さ１０ｍｍの長方形さらに長尺のテープ状など種々寸法を生成可能である。
すなわち、生成条件を種々検討した結果、陰極材質に抵抗率の高い材質を選んだこと、陰極放電発生部を予熱し、陰極放電発生部のＣＮＴ生成速度を高めたことによる。
【０１０９】
（純度）
なお、ＣＮＴ集合体は使用用途によらず、純度が高いほうが望ましい。ここで、少なくともある一面から見た純度が９９％以上であれば、実質的には、特に電子放出源、吸着剤、ろ過材、放熱材としては不純物（以下に、別途説明する）を無視することができる。
また、ＣＮＴ集合体の表面（陽極側の表面）のみに付着した不純物は、ＣＮＴ集合体に対して量が微量であり、また不純物が極めて小さい場合には無視することが可能である。すなわち、本発明に係るＣＮＴ集合体は、非精製状態の（アーク放電直後の堆積ままに同じ）で純度９９％以上が確保されるから、精製処理なしでそのまま工業材料として使用することが可能である。
ここで純度は、特定の視野内にある陰極体積物の全面積に対して、ＣＮＴ集合体が占める面積を合計した合計ＣＮＴ面積の割合を意味し、実質的に所定の体積の陰極堆積物に占めるＣＮＴ繊維の総体積の割合に同じである。
【０１１０】
（不純物）
また、不純物のサイズが、ＣＮＴ繊維の直径、または、各ＣＮＴ繊維同士の間隙と比べて極めて小さい場合には、電子放出源に用いた場合には電界に影響を与えず、また、ろ過材として用いた場合には、不純物の脱落による流体の汚染が少なく、さらに、吸着剤、放熱材など表面積を必要とするものに対しても影響が少ない。
このことから、不純物のサイズが直径１００ｎｍ程度（ＣＮＴ繊維としては太い部類に属する）以下であれば、実質的に害は少ないから、工業的には純度１００％と同等に扱うことが可能となる場合がある。
【０１１１】
さらに、吸着剤、放熱材としてＣＮＴ集合体を用いる場合には、ＣＮＴ集合体を構成するＣＮＴ繊維の実際の表面積が大きいほうが性能が良い。このため、ある一面から観察した純度よりむしろ、ＣＮＴ集合体全体の純度が重要になる。ＣＮＴ集合体の全体について、純度（ＣＮＴ繊維の割合）が８０％以上であれば、前記用途に使用可能である。
なお、ここで言う純度は、ＣＮＴ集合体の全体（後記する密の領域および疎の領域を共に含んだ全体）で見たものであり、局所的な領域（後記する密の領域または疎の領域の一方のみを含む狭い領域）で測定した純度は８０％以下であっても構わない。
【０１１２】
（電子放出特性の利用）
▲１▼電子放出源に用いることができ、これを用いた電気・電子機器、たとえば光電管やフラットパネルディスプレイを容易に製造することが可能となる。
▲２▼ＣＮＴ繊維の細束性および結晶性が優れている特性により、電界放出用電子源として、蛍光表示管やフィールドエミッションディスプレイ（ＦＥＤ）などの陰極材料および電子顕微鏡の探針などへの利用が考えられる。
▲３▼また、ＣＮＴ集合体を電子源として用いることにより、効率の良いイオンやオゾンの発生装置を作ることが可能となると考えられる。これらのイオンやオゾンは脱臭や消臭効果を有すると共に、特にマイナスイオンは人への心理面、生理面において良い影響を及ぼすことが報告されている。
【０１１３】
（電子放出特性の利用−電子放出源の大きさ）
ところで、ＣＮＴを電子放出源として用いる場合、より低い電圧で、より高い電流を実現できる電子放出特性が望まれる。電圧に関して言えば、ＣＮＴの形状効果により電界強度を高めることが有効とされており、そのためにはＣＮＴの高アスペクト比化、特に細径化が有効であると言われている。
しかしながら、ＣＮＴの密度を上げていくと、巨視的に見れば表面はより平滑に近づきＣＮＴ先端の電界強度は低下してゆく。このため、ＣＮＴを高密度に塗布した電子放出源においては、配向を不規則にしてＣＮＴ先端の電界強度を高めるほうが、より電子放出特性が優れているとされている。
【０１１４】
また、電流に関して言えば、構成するＣＮＴ繊維の層数を増やし、一本当りの電流容量を増加させる方法と、一本当りの電流容量はそのままに、ＣＮＴ集合体の密度を増加させる方法がある。
前者の場合、電流容量とＣＮＴの断面積の間に相関があり、電子放出特性にＣＮＴ繊維のアスペクト比が効くことから、自ずと上限を有する。後者の場合、従来の塗布法等によれば、基板に直接接触しているＣＮＴの上に、さらにＣＮＴが積層され、この各々のＣＮＴの接触は少数の点接触となる。この点接触部の電流容量は、ＣＮＴに比べ著しく低く、すぐに焼き切れてしまい、上部に堆積されたＣＮＴは電子放出源として機能しなくなるだけでなく、不純物として電子放出特性を悪化させる。
【０１１５】
この問題に対し、本発明に係るＣＮＴ集合体は、複数本のＣＮＴ繊維が綿状に複雑に絡み合っているから、電子放出特性に優れたＣＮＴ集合体になっている。さらに、ＣＮＴ集合体の表面の各ＣＮＴ繊維の配向は不規則であり、ＣＮＴ繊維の先端の電界強度をより高めることができる。
また、各ＣＮＴ繊維同士の接触についても、多数の接触点を有し、かつＣＮＴ繊維の弾性によりより強固な接触を得られることから、表面を高密度のＣＮＴ集合体とした場合においても十分な電流容量を有することが可能となり、より高い電流を得られる電子放出源を得ることができる。
本発明に係るＣＮＴ集合体の表面のＣＮＴ繊維は不規則に配向されているため、微小面積にすると電子放出特性にばらつきが生じ易く、電子放出源として均質な電子放出特性を得るためには、少なくとも１辺が１ｍｍ以上の長さを有することが必要である。この場合の辺の長さは、円の直径、楕円の長円半径を含む。
【０１１６】
（電子放出特性の利用−ＣＮＴ繊維の大きさ）
前記のごとく、ＣＮＴを電子放出源として用いる場合には、電子放出特性に優れたＣＮＴ繊維の形状を得ることが望ましい。ＣＮＴ先端の電界強度に関しては、ＣＮＴ単体であればアスペクト比により決定されるが、１μｍ以上の長さを持つＣＮＴ繊維であれば、長さの影響をほとんど受けず、ほぼ各ＣＮＴ繊維の直径により電界強度が定まる。
これは、単体のＣＮＴ繊維のほとんどはＣＮＴ集合体の中に埋もれているため、ＣＮＴ集合体の巨視的表面から飛び出したＣＮＴ繊維の突き出し長さおよぼ該突き出した長さ部分の長さと直径とのアスペクト比で電界強度が定まるためである。
【０１１７】
発明者らが試験した結果、直径１５ｎｍ以下のＣＮＴ繊維からなるＣＮＴ集合体であれば電子放出源として十分な電界強度を得ることができた。また、電流容量に関しては、４ｎｍ以上の直径を有するＣＮＴ繊維から構成される集合体であれば、電子放出源として十分な電流容量を得ることができた。
よって、電子放出源としては、４〜１５ｎｍのＣＮＴ繊維によって構成されたＣＮＴ集合体が適していることになる。なお、純度（構成比率）について、直径４〜１５ｎｍのＣＮＴ繊維が５０％以上含まれていれば、これ以外の直径のＣＮＴ繊維や不純物が５０％以下の量混入していても電子放出特性にさほどの影響を及ぼさず、そのまま電子放出源として利用することが可能である。
【０１１８】
（電子放出特性の利用−ＣＮＴ集合体の体積密度）
構成するＣＮＴ繊維が密に集合すると、ＣＮＴ集合体の表面は巨視的に見ればより平滑に近づく。極端な場合、密度１００％の集合体を考えると、表面が平滑な板状物質となり、各々のＣＮＴに印加される電界強度は低下する。
このため、電子放出源として使用するＣＮＴ集合体としては、ある程度疎に集合していることが望ましく、さらに望ましくは、表面から見た場合に綿状に開口部を有していることが望ましい。
【０１１９】
このことから、自ずと電子放出特性に優れた体積密度が定まるが、発明者らが調査した結果、体積密度、言い換えればＣＮＴ集合体の見かけ体積に対するＣＮＴ繊維が占める実体積の割合が１／１０以下であれば、電子放出源として利用でき、さらに１／５０以下とすることで良好な電子放出特性を得ることができた。なお、実際のＣＮＴ繊維集合体はＣＮＴ繊維が複雑に絡み合っており、体積密度を測定することは困難であったため、体積密度に黒鉛の密度を乗じたものと、実際に測定したＣＮＴ集合体の質量の比より体積密度を求めている。
【０１２０】
（電子放出特性の利用−ＣＮＴ繊維の接触間隔）
各々のＣＮＴ繊維の長さが短いＣＮＴ集合体においては、ＣＮＴ繊維同士の接触点が少なくなり、電気伝導性や電流容量の低減を招く。すなわち、接触点の数が多いほど各ＣＮＴ繊維間の電気的接触が確保される一方、電子放出特性を考えた場合には、ＣＮＴ繊維が接触する接触点近傍では、各々のＣＮＴ繊維の電位がほぼ等しいことから（電位差が極めて小さい）電界強度の低下を招き、電子放出のために高い電界強度が必要となる。
【０１２１】
このため、あるＣＮＴ繊維ａに一方のＣＮＴ繊維ｂが接触する一方の接触点ａｂと該あるＣＮＴ繊維ａに他方のＣＮＴ繊維ｃが接触する他方の接触点ａｃとの距離（ａｂ−ａｃ）を接触間隔とすると、接触間隔が狭すぎると電子放出特性が低下する。
このため接触間隔がある程度以上開いていることが必要になる。実際には接触間隔と電界強度の関係は交差角、各々のＣＮＴ繊維の径、周囲形状により変化するが、接触間隔が５μｍ以上離れているものを含むことが望ましい。特に、表面１０μｍ角の視野において、複数本含むことにより良好な電子放出特性を得ることができる。
【０１２２】
（電子放出特性の利用−ＣＮＴ繊維の結晶性）
ＣＮＴ集合体を構成するＣＮＴ繊維の結晶性は、集合体全体としての電子放出特性にも大きく影響する。結晶性が悪い場合、ＣＮＴ繊維自体の電気伝導度が低下し、電流容量が低下するだけでなく、ＣＮＴ繊維の全長もしくは一部が、他のＣＮＴ繊維と絶縁され、電子放出の妨げとなる。
しかしながら、厳密な結晶性の評価はラマン散乱等の手法を用いなければならず、ＣＮＴ集合体の広い面積についてＣＮＴ繊維の結晶性を評価することは困難である。
【０１２３】
図３４は本発明の実施の形態６に係るアーク放電により製造されたＣＮＴの利用についてＣＮＴ繊維の特徴を比較する模式図である。図３４の（ａ）に示す本発明によって生成されたＣＮＴ繊維は、略直線状であって、その直径は略均一であって、途中で枝分かれすることがないものである。一方、図３４の（ｂ）に示す気相成長法（ＣＶＤ法）で生成されたＣＮＴ繊維は、本来直線状に成長するはずのＣＮＴ繊維が曲がりくねって成長したり、途中で枝分かれを起こしたり、長手方向の途中で外径が変化したりしている。
なお、一般の気相成長法（ＣＶＤ法）では、アーク放電法に比べ結晶性が低いとされており、その根拠として、ＣＮＴ繊維の前記屈曲、枝分かれ、径の不均一が挙げられることから、枝分かれがないものが結晶性が良いものであると評価することが可能である。よって、本発明に係る枝分かれのないＣＮＴ繊維によって構成されたＣＮＴ集合体は電子放出源としてより良い性能を有すると考えられる。
【０１２４】
（電子放出特性の利用−ＣＮＴ繊維の絡み合い）
また、ＣＮＴ集合体を電子放出源として用いる場合、ＣＮＴ繊維同士の電気的接触を確実にすること、および結晶性を高めることが重要である。ここで、本来直線状に成長する結晶性のよいＣＮＴが、複雑に絡み合うことにより、ＣＮＴ繊維に弾性変形を生じ、接触を確実にし、各々のＣＮＴ繊維同士の電気的接触性、いわゆる通電性を向上させる効果がある。
【０１２５】
（電子放出特性の利用−ＣＮＴ集合体の疎密領域）
さらに、電子放出源にＣＮＴ集合体を用いる場合、巨視的に見れば、密度は一定であるほうが、ＣＮＴ集合体間における性能のばらつきが小さくなるのは言うまでもないが、微視的に見た場合、疎密がある方が電界強度を高めることができ、電子放出特性は向上する。すなわち、本発明に係るＣＮＴ集合体は、その内部にはＣＮＴ繊維が密に集合した第１の領域と、疎に集合した第２の領域を含んでいるから、良好な電子放出特性を発揮するものと考えられる。
【０１２６】
なお、第１の領域（ＣＮＴ繊維が密に集合した）は、電子放出源としては、より多くのＣＮＴ繊維同士の接触点を有することが望ましく、また、吸着材料または放熱材料としては、より表面積を増やすことが望ましいため、体積密度１（嵩比重１．８ｇ／ｃｍ³、中実に同じ）に近づくことが望ましい。しかしながら、綿状のＣＮＴ集合体を形成するためには、ある程度の空隙を許容する必要がある。また、第２の領域と明確に異なる領域と認識するため、すなわちＣＮＴ集合体が疎と密の領域を持つことを定義するために、体積密度１／５以上（嵩比重０．３６ｇ／ｃｍ³）である領域を密の領域と定義する。
【０１２７】
一方、第２の領域（ＣＮＴ繊維が疎に集合した）は、電界強度の面から言えば理想的には一本もＣＮＴ繊維が含まれないことが望ましいが、現実には、体積密度１／１００（０．０２２５ｇ／ｃｍ³）以下であればよい。すなわち、体積密度１／１００以下の場合、隣り合ったＣＮＴ繊維との間隔は、２次元的に平均観察すると、ＣＮＴ繊維の直径の10倍以上であるから、実際の３次元空間に不規則に配置された状態では、ＣＮＴ繊維の直径の３０倍以上を有していることになり、一本も含まれない領域であるのと同等に考えることができる。
さらに、かかる疎密を判断する基準の体積は、視野の大きさによって相違する。このため、電界強度の強弱を高めるために電子放出特性を評価するためには、一辺２μｍの直方体を切り出した領域を視野にすることが望ましい。
【０１２８】
（電子放出特性の利用−ＣＮＴ集合体の疎密領域の凹凸）
さらに、本発明に係るＣＮＴ集合体は、その表面にＣＮＴ繊維が密に集合している領域と疎に集合している領域とがある。該密に集合している領域は先端が尖った円錐形状として凸になっている。この凸になっている領域には、ＣＮＴの端部を多く含み、他のところに比べ凸になっているため、形状効果による高い電界強度と相まって電子放出能が高い。さらに、この凸になっている領域がほぼ均一に分布して存在していることから、ＣＮＴ集合体の面として見た場合の電子放出電流密度の分布も巨視的に見ればほぼ均一にすることができる。
【０１２９】
さらに、本発明に係るＣＮＴ集合体の凸部（密に集合している領域）は、根元側(開放空間と反対側、陰極側に相当)は多数のＣＮＴ繊維により、通電経路を多く持つことから、より多くの電流を流すことが可能である。加えて、先端（陽極側に相当、または、破断面側に相当）に向うに従い構成するＣＮＴ繊維の本数が徐々に減じ、凸の領域の先端は、一本ないし小数本のＣＮＴとなっている。
このため、先端が尖ったっことによる効果と、突状である形状効果により電界強度を高めるという顕著な電子放出源特性を発揮している。さらに、後記するように、この尖った部分をＣＮＴ集合体の表面に対して、開放空間側に積極的に引き出すことによりさらに優れた電子放出特性が得られる。
【０１３０】
（電子放出特性の利用−ＣＮＴ集合体の疎密領域の間隔）
ＣＮＴを電子放出源として用いる場合には、電子放出特性に優れることと、電子放出面における電子放出電流密度の均一性を確保する必要がある。そのためには、表面が開放空間に向かい凸になっている電界強度が高まる部分と、凹になっており電界強度が低くなる部分が、ある程度密にかつ均一に分布していることが望まれる。
【０１３１】
この間隔の適正値は、当然のことながら、対象となる製品や、電子放出源の大きさ、特に面積にも左右される。しかしながら、たとえば、３００ｄｐｉの解像度を有するフラットパネルディスプレイを考えたとしても、各々の発光部は一辺８０μｍの正方形であり、この凸の領域の間隔が４０μｍ以下であれば、この解像度においても必ず複数個の凸の領域を各々の発光部に含むことになる。
また、現在、比較的高解像度であるコンピュータの液晶ですら、１５０ｄｐｉ程度であることを考えると、凸の領域の間隔が４０μｍ以下、さらに好ましくは２０μｍ以下であれば電子放出源の均一性としては、実用上問題ないと考えられる。
【０１３２】
また、この凸の領域同士の間隔が極めて小さい場合を考えると、ＣＮＴ集合体の電子放出面はより平滑化し、形状効果による高い電界強度が得にくくなる。このため、少なくともＣＮＴ繊維の直径に対して１００倍以上の間隔を有することが望ましく、電子放出特性に優れたＣＮＴ繊維の直径が２０ｎｍ以下であることを考えると、この凸領域同士の間隔は２μｍ、さらに好ましくは５μｍ以上の間隔を有して分布していることが望ましい。
【０１３３】
このことから、工業的には電子放出面のうち、一辺４０μｍの視野において、少なくとも隣り合った間隔が２〜４０μｍ、さらに好ましくは５〜２０μｍの間隔をおいて凸形状にＣＮＴが集合した領域が存在することが望ましい。
なお、この隣り合った間隔の上限は、電子放出源として用いた場合の、電子放出領域の半径相当距離（たとえば、矩形の電子放出領域の一辺の長さ（たとえば一辺２００μｍの正方形の電子放出源においては１００μｍ）、すなわち、電子放出領域の面積の平方根の半分）であれば、均一性としては問題なく所定の性能を発揮する。さらに好ましくは電子放出源領域の半径の半分（電子放出領域の面積の平方根の１／４、前記の例で言えば５０μｍ）であっても、均一性としては問題なく、特に高い電子放出電流を必要としない場合には、この値を用いることも可能である。この場合の視野は電子放出源一領域の面積であることは言うまでもない。
【０１３４】
（電子放出特性の利用−ＣＮＴ集合体の密領域を構成するＣＮＴ繊維）
さらに、ＣＮＴ集合体に疎密領域を形成するためには、これを含まれるＣＮＴ繊の長さが１０μｍ以上である必要がある。
すなわち、疎に集合した領域と密に集合した領域を有したＣＮＴ集合体を形成するためには、少なくとも、密に集合した領域を跨ぐ長さのＣＮＴ繊維を含むことが必要であるから、密に集合している領域の間隔が５〜２０μｍであるとき、疎に集合した領域（密に集合している領域の中間に位置する）は平均的に１０μｍの広がりを持つことになるから、これを跨ぐ１０μｍ以上のＣＮＴ繊維が必要になる。
【０１３５】
加えて、ＣＮＴ繊維は非常に小さく、またＣＮＴ繊維間の距離もきわめて小さいため、各々のＣＮＴ繊維間には分子間力が働き、互いに引き寄せ合っている。この、分子間力は極めて小さいが、ＣＮＴ繊維が十分長ければ、ＣＮＴ繊維の成長に伴い、徐々に引き寄せ合って、ついに密に集合した領域と疎に集合した領域とが生成されることも考えられる。
一方、ＣＮＴ繊維の長さが１０μｍに満たない場合には、疎に集合している部分におけるＣＮＴ繊維同士の結合が弱く(接触点数そのものも少なくなり)集合体として形成できないと考えられる。
【０１３６】
（電子放出特性の利用−ＣＮＴ繊維の先端）
複数のＣＮＴ繊維が絡み合い、綿状に一体化した集合体を分割すると（図３２参照）、分割面から開放空間に向かい、端部を有したＣＮＴ繊維が伸びている。これは、ＣＮＴ繊維が元々直線状に成長することと、分割面付近の一部の端部を有するＣＮＴ繊維に加わる拘束力が変化または開放し、他からの拘束によって円弧状に曲がっていたＣＮＴ繊維が直線状に戻ったものと考えられる。
また、一部は、分割時の変形力により、強制的に分割面から開放空間へ向かうよう再配向されたと考えられる。何れか、この分割面から開放空間に伸びた端部を有するＣＮＴ先端には、形状効果により高い電界強度を有し、電子放出源として用いる場合には高い電子放出特性を得ることができる。
【０１３７】
図３５は本発明の実施の形態６に係るアーク放電により製造されたＣＮＴの利用についてＣＮＴ繊維の特徴を示す模式図である。図３５の（ａ）は引っ張り加工（図３０参照）によって先端が破れたＣＮＴ繊維を示し、図３５の（ｂ）は同様に先端が破れた中実のＣＮＴ繊維を示している。何れかも、チューブを形成するグラフェンシートの端部（破断面）が空間に露出している。
これより、前記高い電子放出特性の理由は以下のように考えられる。
【０１３８】
（理由１）本発明に係るＣＮＴ集合体は、その表面にのみ不純物が僅かではあるが見受けられた（生成過程もしくはその後に付着）。電子放出源として使用する場合にこれらの不純物は、電子放出に寄与しないばかりか、マスクとして作用し、表面の電子放出を妨げる。このため、できるだけ不純物を取り除き、集合体内部の清浄部を表面に露出させることが望ましい。
【０１３９】
（理由２）電子放出特性を高めるためには、形状効果によって電界強度が高くなるから、ＣＮＴ繊維の先端を表面に多く露出させることが望ましい。
すなわち、本発明に係るＣＮＴ集合体を引き千切ることにより、ＣＮＴ繊維の端部が多く露出する。これは、綿を引き千切ったときに、破断面に繊維の先端が多く露出することからも容易に想像できる。
【０１４０】
（理由３）本発明においては、ＣＮＴ集合体に引張力を加えることにより、綿状に複雑に絡み合っているＣＮＴ繊維は解きほぐされたり、または破断されたりするから、その破断面には、解きほぐされたＣＮＴ繊維の端部、およびある確率で破断されたＣＮＴ繊維が引っ張り方向に配向された状態で破断端部が現れる。この破断面には当然のことながらＣＮＴ繊維を形成している各層のグラフェンシートの端部が露出し、高い電子放出特性を有する。
【０１４１】
なお、ＣＶＤ法等によって生成されたＣＮＴ（たとえば、カーボンナノホーン）で、チューブ上の炭素繊維の両端が円錐形に完全に閉じた構造になっているものに対し、酸化処理等でチューブの両端の炭素結合を破壊してチューブの先端にチューブを構成しているグラフェンシートの端部を露出させることにより、電子放出特性を向上させることができるという報告がなされている。
【０１４２】
（低い体積密度、表面積の利用）
▲１▼ＣＮＴ集合体の体積密度は黒鉛の１／１０以下であり、各ＣＮＴ繊維が複雑に絡み合っていることから、ろ過材として使用可能である。
▲２▼さらに、実効の表面積が大きいことから、活性炭と同様に吸着剤として使用可能であり、重量当りの吸着量は活性炭に比べ大きいことが予想される。
▲３▼従来手法で作られたＣＮＴは単体の大きさが小さく、直径７０ｎｍ以下、長さ１０μｍ未満のものが弱い機械的接合で、言うなれば、堆積、付着しているだけであり、流体が流れることで接合が解かれ、粉体と共に流れていくのに対し、本発明の集合体は流体の中においても崩れにくいことから、集合体そのものを前記機能膜もしくは機能体としてそのまま使用可能である。
▲４▼ナノサイズの直径を持つＣＮＴが複雑に絡み合った綿状のＣＮＴテープは、その密集度から決まるある大きさの空間を有しているため、特定の大きさを有する物質を選別するためのフィルタや分離膜としての利用が考えられる。
▲５▼また、その単位重量あたりの表面積の大きさは、活性炭をも凌ぐものであり、有害物質の吸着材や、水素やメタンなどのガス貯蔵材としての利用が考えられる。
【０１４３】
図３６は本発明の実施の形態６に係るアーク放電により製造されたＣＮＴを利用したフィルタを説明する概略図である。図３６において、Ｆ１は流体導入口Ｆ２と流体排出口Ｆ５の間に、筒状のろ過部Ｆ３を有し、ろ過部Ｆ３にろ過体が配置されている。該ろ過体は複数のＣＮＴ集合体Ｃ２１が平面状に配置された集合体層によって形成され、該集合体層が単層のまま又は複数が積層された状態でその表裏面が集合体保持手段Ｆ４によって保持されている。これにより、流体が通過する際にＣＮＴ集合体が撹拌されて粉々に千切れることが防止される。
これらを、用いることにより液中もしくは気体中の特定物質のみを透過する、ろ過装置や特定物質を吸着するフィルタ、または脱臭装置などへの応用も期待できる。なお、ＣＮＴ集合体とは前記ＣＮＴテープまたは加工片であってもよい。
【０１４４】
（放熱特性の利用）
▲１▼本発明に係るＣＮＴ集合体をアルミ板に取り付け放熱特性を測定したところ、集合体なしの場合に比べ、２０％放熱効果が向上した。これは、集合体そのものの放熱特性、たとえば綿状であることよりの実効表面積の大きさ、長いＣＮＴが多くの熱伝達の良い接触点を持つことによる熱伝導性の良さから起因していると考えられる。
すなわち金属板に限らずたとえば、半導体集積回路に貼ることで放熱性能を向上させることも期待できる。付け加えれば、熱伝導の高さを活かし、伝熱材料たとえば冷却フィンと被冷却物の間に挟むことで、密着性を高めるのと同時に効率よく熱を伝えることも利用の一例として考えられる。
【０１４５】
（引っ張り強度の利用）
▲１▼結晶性が優れているということは、ＣＮＴの強度が高いことを意味している。すなわち、ＣＮＴ繊維は、理論的には鉄の１００倍以上の引張強度を有し、比重はアルミニウムの約半分であるため、樹脂や金属に混入したり、樹脂や金属とＣＮＴとの複合化により、軽くて強度の高い構造材料を造ることができる。
▲２▼また、その名のとおり、ナノサイズの大きさであるので、マイクロマシンの構造部材やアクチュエータの構成部品としての利用も考えられる。
【０１４６】
なお、複数のＣＮＴ繊維が一体化するためには、何がしかの力でＣＮＴ繊維が結合する必要がある。たとえばＣＮＴ繊維が全て直線状である場合には、ＣＮＴ繊維間の結合が基本的には分子間力、もしくは摩擦力のみとなる。
無論、複数本のＣＮＴ繊維を考えた場合、複雑に挟み込むことで接合力を確保することは可能であるが、外力、たとえば引っ張り力が加わった場合を考えると、各々のＣＮＴ繊維は外力方向または変形方向に配向するものと容易に想像される。このようにほぼ一方向に配向されたＣＮＴ繊維同士の結合は、分子間力、もしくは摩擦力のみになる。
【０１４７】
これに対し、曲線状の形態を持つＣＮＴ繊維は他の複数のＣＮＴ繊維と絡むこと、さらにＣＮＴ同士を結び合った状態となり、分子間力、摩擦力に加えて他のＣＮＴ繊維とのせん断力、引っ張り力等、種々の力が加わる。このため、ＣＮＴ繊維自体の強度は鋼よりも強く、ＣＮＴ集合体としてはより強く一体化するため、所定の強度を有する。すなわち、比較的小さな力、たとえばＣＮＴ集合体を持ち上げる力、液に浸した場合に作用する外力等に対しても分解せずＣＮＴ集合体のままで存在することが可能となる。
したがって、所定の曲率をもって湾曲したＣＮＴ繊維を３０％以上含むＣＮＴ集合体であれば、所望の強度を確保することができる。
【０１４８】
ＣＮＴ集合体として取り扱うためには、言うまでもないが、各々のＣＮＴ繊維が高い強度を有することが望ましい。
ＣＮＴには、グラフェンシートを１層しか有しない単層ＣＮＴ、２層有する２層ＣＮＴ、３層以上有する多層ＣＮＴに大別されるが、強度の面では層数が多い方が強く、ＣＮＴ集合体を構成するＣＮＴ繊維としては、多層ＣＮＴのみで構成されることが望ましい。
しかしながら、ＣＮＴの生成メカニズムが完全に解明しておらず、また、構成するＣＮＴ繊維の数量も、数万〜数億本もしくはそれ以上の本数となるため、多層ＣＮＴのみで構成されているとは言い切れない。
よって、実質的に多層ＣＮＴで構成されていれば、強度的に集合体として取り扱いが可能なため、たとえば、９５％以上の構成比で多層ＣＮＴを含むことが好ましい。
【０１４９】
なお、本発明に係るＣＮＴ繊維の多くが曲率半径１μｍ以上曲率半径１０μｍ以下のものを含むものであるのに対し、気相成長法（ＣＶＤ法）で作られるＣＮＴ繊維は結晶性の悪さから屈曲（曲率半径がおおよそ１００ｎｍオーダである）し、概してＣＮＴ繊維の強度が低いため切断され易いものである。
【０１５０】
また、前記のごとく本発明に係るＣＮＴ繊維の結晶性が良く強度が高いこと、および各々のＣＮＴ繊維が弾性変形して、変形能が高く、変形に対してもＣＮＴ繊維の破断が起こり難い。さらに、各々のＣＮＴ繊維が長いため、集合体としても破断しにくいという特徴を持つ。
このため、ＣＮＴ生成時に絡み合った綿状の構造体として得られるＣＮＴ集合体は、ＣＮＴ繊維同士が複雑に絡まって機械的に強固に結合し、ＣＮＴ集合体からの分離、脱落を抑制している。
このことは、各種材料としてのＣＮＴ集合体のハンドリングを向上させ、球面、曲面基板に取り付けて使用することを可能とする。
【０１５１】
一方、ＣＶＤ法等の別プロセスにて製造されたＣＮＴ繊維は各々が絡み合っていない。また、紛体状のＣＮＴを撹拌等の処理によって製造した場合は、本来独立しているＣＮＴを後工程において簡単に機械的に絡み合わせたただけであるため、ほぐれ易く、ハンドリング等の際、ほぐれたＣＮＴが滓となり、脱落したり、電気的導通を失い、不純物となることが考えられる。さらに、流れる気体や液体に曝される場合にはこの傾向が顕著になる。
【０１５２】
（導電性の利用）
▲１▼また、導電性が優れているため、ＩＣの配線材料としての利用が考えられる。
▲２▼樹脂や繊維に混入することにより、これらの物質に導電性を持たせたり、静電気の帯電防止機能を持たせることができる。
▲３▼塗料に混入させた導電性塗膜や導電性インクへの利用も考えられる。
これらのものは、導電性を必要とする部材に利用できると共に、電磁波の反射損失や誘電損失に基づく電磁波吸収・遮蔽材としても利用できる。
▲４▼また、二次電池の負極材料に混入させることにより、負極導電性の経年劣化を防止することができる。
▲５▼さらに、グリスに混入させることで、グリスに導電性を持たせると共に、通電部でのグリスの性能劣化を防止することができると考えられる。
▲６▼キャパシターの電極材料としての利用も考えられる。
【０１５３】
（導電性の利用−ＣＮＴ繊維同士の接触）
各々のＣＮＴ繊維の長さが短いＣＮＴ集合体においては、ＣＮＴ繊維同士の接触点が少なくなり、電気伝導性や電流容量の低減を招く。さらに、各々のＣＮＴ繊維の長さを長くし、複雑に絡み合わせることによりＣＮＴ繊維同士の接触力を高め、電気伝導性や電流容量の向上を行える。このためには、大部分、具体的にはＣＮＴの構成比の５０％以上、さらに好ましくは８０％以上の比率で、長さ10μｍ以上のＣＮＴ繊維を含むことが必要である。
図３７は本発明の実施の形態６に係るアーク放電により製造されたＣＮＴの利用についてＣＮＴ繊維の特徴を示す模式図である。
例えば、ＣＮＴ繊維を直列に接続した場合を考え、従来技術で作られるＣＮＴ繊維の長さを１μｍ（図３７の（ａ））、本発明の集合体に含まれるＣＮＴ繊維の長さを１０μｍ（図３７の（ｂ））とすると、同じ回路長さを構成する場合のＣＮＴ繊維同士の接触点は１／１０に減少する。
接触点における抵抗率は、ＣＮＴ繊維単体の抵抗率に対して大きいことから、接触点を減らすこと、すなわちＣＮＴ繊維の長さを長くすることにより、集合体としての導電性を高めることができる。
【０１５４】
また、前記のＣＮＴ繊維が同じ密度にて格子状に接続されたの場合を考えると、１μｍ長のＣＮＴ繊維Ｆ１とＣＮＴ繊維Ｇ１とによって形成された格子の接触点（図３７の（ｃ））と、１０μｍ長のＣＮＴ繊維Ｆ１０とＣＮＴ繊維Ｇ１０とによって形成された格子の格子点（図３７の（ｄ））とでは、ＣＮＴ繊維の長さが長い後者の方が増える、言い換えれば、より多くの通電経路を有することとなり、並列接続の効果として集合体の導電性を高めることができる。
よって、ＣＮＴ繊維の長さは長いほど、例えば、２０μｍや５０μｍ超の方が集合体の導電性を向上させる効果があるが、複雑に絡み合った綿状の集合体を構成するため、たとえば、１０μｍ長さ以上のＣＮＴ繊維が５０％以上、または３０μｍ長さ以上のＣＮＴ繊維が４０％以上、または５０μｍ長さ以上のＣＮＴ繊維が３０％以上のいずれかの構成比で含まれていればよい。
【０１５５】
（熱伝導性の利用）
▲１▼ＣＮＴはダイヤモンド以上の熱伝導性を有しているため、ＩＣなどの放熱材としての利用も考えられる。放熱材として利用する場合は、単体でも、または、樹脂や金属に混入したものを用いても良い。また、アルミ板などの表面に塗布もしくは貼り付けることによっても放熱特性を大きく向上させることができるものと思われる。
【０１５６】
（量子効果の利用）
▲１▼さらに、ナノサイズのきわめて小さな構造体であるＣＮＴは、量子効果を利用したダイオードやトランジスタ、および量子コンピュータの基本素子である量子ドットなどの電子部品の材料としても利用できるものと考えられる。
【０１５７】
（機能性の利用）
▲１▼また、特定ガスを検出するガスセンサなど機能材料としての利用も考えられる。
▲２▼さらに、触媒の担持材として利用することによって、各種化学反応の効率を向上させることが可能になると考えられ、
▲３▼さらには、医療分野等において、薬剤等を吸着・保持させて体内の病巣部へ運搬するキャリヤーとして利用できる可能性がある
【０１５８】
【発明の効果】
以上のように本発明においた、ＣＮＴ繊維同士が十分に絡まりあい、ＣＮＴ純度の高いＣＮＴ集合体、および該ＣＮＴ集合体を設置したＣＮＴ設置装置が得られる
【図面の簡単な説明】
【図１】本発明の実施の形態１に係るアーク放電によって生成されたＣＮＴの製造方法におけるＣＮＴ製造装置の実施例１（ＣＮＴ製造装置１）を示す模式図である。
【図２】本発明のＣＮＴ製造装置２（冷却陽極）を示す模式図である。
【図３】本発明のＣＮＴ製造装置３（予熱陰極）を示す模式図である。
【図４】本発明のＣＮＴ製造装置４（ガス供給陽極）を示す模式図である。
【図５】本発明のＣＮＴ製造装置５（ノズル付き陽極）を示す模式図である。
【図６】本発明のＣＮＴ製造装置６（移動陽極）を示す模式図である。
【図７】本発明のＣＮＴ製造装置７（回転陰極）を示す模式図である。
【図８】ＣＮＴ製造装置２（冷却陽極）におけるアーク放電部の温度測定の結果を示すサーモビューア写真である。
【図９】ＣＮＴ製造装置２（冷却陽極）におけるアーク放電部の温度測定の結果を示すサーモビューア写真である。
【図１０】本発明の実施の形態３に係るＣＮＴの製造方法の実施例１（ＣＮＴ製造方法１）を示す模式図である。
【図１１】図１０の一般放電によりアークを短時間発生させた場合の陰極点を観察した結果を示す走査型電子顕微鏡（ＳＥＭ）写真である。
【図１２】本発明のＣＮＴ製造方法３（予熱陰極）を示す模式図である。
【図１３】本発明のＣＮＴ製造方法４（ガス供給陽極）におけるアーク放電状況を示す模式図である。
【図１４】本発明のＣＮＴ製造方法４（ガス供給陽極）において生成されたＣＮＴを示す走査型電子顕微鏡（ＳＥＭ）写真である。
【図１５】本発明のＣＮＴ製造方法４における放電用ガスの流量とアーク発生形態との関係を示す実験結果のグラフである。
【図１６】本発明のＣＮＴ製造方法４における放電用ガスに触媒粉末を混入される状況を説明する模式図である。
【図１７】本発明のＣＮＴ製造方法６（移動するガス供給陽極）を示す模式図である。
【図１８】本発明のＣＮＴ製造方法６（移動するガス供給陽極）における高純度ＣＮＴテープの生成機構を推定した模式図である。
【図１９】本発明のＣＮＴ製造方法６の２によって生成された高純度ＣＮＴテープを示す電子顕微鏡写真である。
【図２０】本 発明のＣＮＴ製造方法７（ガス供給陽極）を示す模式図である。
【図２１】本発明のＣＮＴ製造方法７（ガス供給陽極）において生成された高純度ＣＮＴテープの外観写真である。
【図２２】本発明のＣＮＴ製造方法７（ガス供給陽極）において生成された高純度ＣＮＴテープのＳＥＭ写真である。
【図２３】本発明のＣＮＴ製造方法７の２（移動するガス供給陽極と冷却ガス吹き付け）におけるアーク放電状況を示す模式図である。
【図２４】本発明のＣＮＴ製造方法７の３（移動するガス供給陽極と陰極加熱）おけるアーク放電状況を示す模式図である。
【図２５】本発明の実施の形態４に係るアーク放電によって生成されたＣＮＴを示す電子顕微鏡写真であって、（ａ）は外観写真、（ｂ）は電子顕微鏡写真である。
【図２６】本発明の実施の形態４に係るアーク放電によって生成されたＣＮＴを示す電子顕微鏡写真である。
【図２７】図２５に示すＣＮＴ繊維の太さの測定結果を示す分布図である。
【図２８】本発明の実施の形態４に係るＣＮＴの結晶性を説明する模式図である。
【図２９】本発明の実施の形態４に係るＣＮＴを示す透過電子顕微鏡写真である。
【図３０】本発明の実施の形態５に係るＣＮＴの引っ張り加工状況を説明する模式図である。
【図３１】本発明の実施の形態５に係るＣＮＴを引っ張り加工した後の側面を示す電子顕微鏡写真である。
【図３２】本発明の実施の形態５に係るＣＮＴの引き剥がし加工状況を説明する模式図である。
【図３３】本発明の実施の形態５に係るＣＮＴの加工後の表面を示す電子顕微鏡写真である。
【図３４】本発明の実施の形態６に係るＣＮＴの利用についてＣＮＴ繊維の特徴を比較する模式図である。
【図３５】本発明の実施の形態６に係るＣＮＴの利用についてＣＮＴ繊維の特徴を示す模式図である。
【図３６】本発明の実施の形態６に係るＣＮＴを利用したフィルタを説明する概略図である。
【図３７】本発明の実施の形態６に係るＣＮＴの利用についてＣＮＴ繊維の特徴を示す模式図である。
【符号の説明】
１ ＣＮＴ製造装置、 １０ 陽極、 ２０ 陰極、
３０ チャンバ、 ３１ 陽極ホルダ、 ３２ 陰極ホルダ、
３３ 内壁、 ３４ 陽極移動手段、 ３５ 通電手段、
Ｃ２１ テープ状の物質、 Ｔ２１ 陰極堆積物、 Ｔ２２ 陰極煤、
Ｔ２３ 付着物質、 Ｔ３３ チャンバ煤、 ５０ 陽極冷却手段、
６０ 陰極予熱手段、 ７０ 放電用ガスノズル、８０ 陽極移動機構、
９０ 陰陽極移動機構[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a carbon nanotube aggregate and a carbon nanotube installation device provided with the same.
[0002]
[Prior art]
(carbon nanotube)
Carbon nanotubes are mainly produced by the laser evaporation method (chemical method) or the arc discharge method (physical method). A sheet in which carbon atoms are regularly arranged in a hexagonal or pentagonal shape (hereinafter referred to as a graphene sheet) is formed into a cylindrical shape. It is curled and has attracted attention as a new material because of its unique properties.
A single graphene sheet tube is called a single-walled carbon nanotube (SWCNT), and its diameter is 1 to several nm. On the other hand, a graphene sheet in which multiple cylinders are concentrically overlapped is referred to as a multi-walled carbon nanotube (MWCNT) and has a diameter of several nm to several tens nm. A graphene sheet curled in a substantially conical shape is called a carbon nanohorn, and there is a single-layer or multilayer carbon nanohorn (SWCNH, MWCNH). In the present invention, these are collectively referred to as carbon nanotubes (hereinafter, referred to as CNT). The CNT alone is referred to as CNT fiber, and the CNT fiber aggregate is referred to as a CNT aggregate.
[0003]
(Vapor phase generation method)
In the vapor phase generation method, a raw material gas (a raw material vapor for generating CNT fibers diluted with a carrier gas) is supplied into a reaction tube and heated, and the generated CNT is discharged into or from the reaction tube. And collect them.
In addition, the CNT fiber produced by this method has insufficient electron emission characteristics and mechanical strength, partly because the CNT fiber has minute projections or irregularities on the surface and is not smooth, or is branched. There are cases. In addition, since the mixing ratio of impurities is high, it is essential to perform an operation of purifying the recovered product.
[0004]
(Arc discharge method)
The arc discharge method uses arc discharge to evaporate carbon, causing arc discharge between carbon electrodes to sublimate carbon from the hot anode side and deposit carbonaceous material directly aggregated at the tip of the cathode. And CNTs are generated in the soot scattered around the arc.
In particular, multilayer CNT fibers, which are formed by concentrically laminating a graphite cylinder in which a graphene sheet is round and closed into a cylindrical shape without a seam and densely packed up to the center of the cylinder, have only excellent electron emission characteristics. Instead, it is excellently mechanically strengthened by being mixed with a composite material like whiskers and the like. This multilayer CNT fiber is considered to be one of the reasons for the excellent characteristics because the graphene sheet at the tip portion of the multilayer CNT fiber is broken (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-2000-327317 (page 5-6, FIG. 3)
[0006]
[Problems to be solved by the invention]
However, the multilayer CNT fiber having a diameter of 10 to 100 nm and a length of 1 μm or more is obtained depending on the manufacturing conditions, but a long one of 10 μm or more is estimated to be difficult to produce. When the fibers are aggregated, the multilayer CNT fibers are not sufficiently entangled with each other, and thus have the following problems.
(A) A multilayer CNT aggregate having a desired size (thickness in side view, spread in plan view, etc.) cannot be obtained.
(B) A multilayer CNT aggregate having a desired mechanical strength cannot be obtained.
(C) It is difficult to process to a desired size.
(D) Since it is a powder of fine particles, it is easily scattered during handling and handling is difficult.
(E) On a predetermined surface of the multilayer CNT aggregate, the multilayer CNT fibers cannot be oriented in a predetermined direction.
(F) As a method of using the multilayer CNT fibers as an aggregate, application of a paste containing powdery CNT fibers can be considered, but there are the following problems.
{Circle around (1)} The conductivity or heat transfer between the CNT fiber and the substrate deteriorates.
{Circle around (2)} Insufficient CNT content (low purity) results in insufficient functions such as electron emission and adsorption.
{Circle around (3)} The CNTs are excessively adhered to each other, and the effective surface area of the CNTs is reduced.
{Circle around (4)} The coated surface cannot be microscopically smoothed to increase the electrolytic strength.
(G) In order to increase the purity after the production, a purification operation in which heating is performed in the atmosphere is required, and thus there is a problem that the production apparatus and the production process become complicated.
[0007]
The present invention has been made in order to solve such problems, and provides a CNT aggregate having a high CNT purity, in which the CNT fibers are sufficiently entangled, and a CNT installation device in which the CNT aggregate is installed. is there.
[0008]
[Means for Solving the Problems]
The aggregate of carbon nanotubes of the present invention is as follows.
(1) A carbon nanotube aggregate in which a plurality of carbon nanotubes are entangled and integrated, wherein the carbon nanotube aggregate contains at least 80% by volume of carbon nanotubes in a non-refined state. .
(2) A carbon nanotube aggregate in which a plurality of carbon nanotubes are intertwined and integrated, wherein the carbon nanotube aggregate contains 99% or more by volume of carbon nanotubes in a non-refined state. .
[0009]
(3) The method according to (2), wherein an impurity composed of a mixture of one or both of carbon and ash other than the granular or film-like carbon nanotubes is contained therein in a volume ratio of 1% or less. is there.
(4) In the above (2) or (3), an impurity composed of one or both of carbon and ash other than granular or film-like carbon nanotubes adheres to the surface, and the volume ratio of carbon nanotubes as a whole is reduced. It is characterized by being 80% or more.
[0010]
(5) In the above (3) or (4), the impurities attached to the surface or the inside of the product are in the form of particles having a diameter of 100 nm or less.
(6) In any one of the above (1) to (5), it is characterized by having flexibility.
[0011]
(7) In any one of the above (1) to (6), it is generated by an arc discharge method.
(8) In any one of the above (1) to (7), the maximum distance between the end portions of the planar region viewed from a predetermined direction is 1 mm or more.
[0012]
Further, the carbon nanotube installation device of the present invention is as follows.
(9) An electron emission source provided with the aggregate of carbon nanotubes according to any one of (1) to (8).
(10) In the above (9), the carbon nanotube aggregate has an area of 0.01 mm in a planar region viewed from a predetermined direction. ^Two The above is the feature.
[0013]
(11) An electric device or an electronic device provided with the carbon nanotube aggregate according to any one of (1) to (8).
(12) A separation membrane provided with the aggregate of carbon nanotubes according to any one of (1) to (8).
[0014]
(13) An adsorbent or an adsorbent provided with the aggregate of carbon nanotubes according to any of (1) to (8).
(14) A purifying apparatus in which the carbon nanotube aggregate according to any one of (1) to (8) is installed.
(15) A heat dissipation material provided with the carbon nanotube aggregate according to any one of (1) to (8).
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the manufacturing apparatus for generating CNT in Embodiment 1, the electrode material suitable for the manufacturing apparatus in Embodiment 2, the manufacturing method for generating CNT in Embodiment 3, and the manufacturing method for generating CNT in Embodiment 4 will be described. Embodiment 5 describes the processing of CNT in Embodiment 5, and the use of CNT in Embodiment 6.
[0016]
[Embodiment 1]
(CNT production equipment 1-fixed solid anode)
FIG. 1 is a schematic diagram showing Example 1 (hereinafter, referred to as CNT manufacturing apparatus 1) of a CNT manufacturing apparatus in a method of manufacturing CNT generated by arc discharge according to Embodiment 1 of the present invention. In FIG. 1, 1 is a CNT manufacturing apparatus, 10 is an anode, 20 is a cathode, 30 is a chamber, 31 is an anode holder, 32 is a cathode holder, 33 is an inner wall (ceiling surface, side surface, floor surface, etc.) of the chamber 30, 34 Is an anode moving means for moving the anode 10, and 35 is an energizing means.
T21 is a cathode deposit deposited on the surface 21 of the cathode 20, T22 is a cathode soot deposited on the side surface 22 of the cathode 20, and T33 is a chamber deposited on the inner wall 33 (ceiling surface, side surface, floor surface, etc.) of the chamber 30. It is soot.
The generated CNTs exist in the cathode deposit T21, the cathode soot T22, and the chamber soot T33.
[0017]
(anode)
The anode 10 is a carbon material or a mixed material obtained by mixing a catalytic substance having a catalytic action of CNT synthesis (described separately below). The anode 10 is formed in a solid rod-like body or a hollow cylindrical body, is gripped by an anode holder 31 installed in a chamber 30, and is connected to a DC power source for arc discharge (not shown) via a current supply unit 34. .
[0018]
(cathode)
The cathode 20 is a carbon material or a mixed material obtained by mixing a catalytic substance having a catalytic action of CNT synthesis (described separately below). The cathode 20 is formed in a plate shape or a rod shape (solid or hollow), is gripped by a cathode holder 32, and is connected to a DC power supply for arc discharge (not shown).
Instead of the mixed material, a material in which a catalyst substance is attached to the surface of a carbon material may be used (described separately below).
[0019]
(Chamber)
The chamber 30 is for capturing the scattered soot, and is hermetically closed. An atmosphere (atmospheric pressure or reduced pressure) of an inert gas such as argon gas or a mixed gas containing an inert gas (hereinafter, referred to as a discharge gas) is used. ) Is formed, or a part thereof is opened, and the whole is made to be in the air atmosphere, and only in the vicinity of the arc discharge generating portion, the atmosphere of the discharge gas is locally formed.
Further, in FIG. 1, the anode holder 31 and the cathode holder 32 are installed in the chamber 30, but the present invention is not limited to this, and a separate frame is provided and the anode holder 31, the cathode holder 32 and the chamber are provided. 30 may be separately installed.
In particular, when the chamber 30 is open (when it is not a closed type), the chamber 30 can be arranged to be limited to a range necessary for capturing soot. It may be a cover. Further, when the generation of soot is small, the chamber 30 may be removed.
[0020]
(CNT production equipment 2-cooling anode)
FIG. 2 is a schematic diagram showing Example 2 (hereinafter, referred to as CNT manufacturing apparatus 2) of the CNT manufacturing apparatus in the method for manufacturing CNT generated by arc discharge according to Embodiment 1 of the present invention. In FIG. 2, 2 is a CNT manufacturing apparatus, 40 is a power supply for arc discharge, and 50 is an anode cooling means. The same parts as those in FIG. 1 are denoted by the same reference numerals, and a part of the description will be omitted.
The anode 10 is formed of a carbon material or a metal material, and an anode cooling means 50 is fitted on the outer periphery. The anode cooling means 50 is, for example, a hollow cylindrical body made of copper, through which cooling water flows. Therefore, overheating of the anode 10 can be prevented by cooling by the anode cooling means 50.
[0021]
Therefore, when the anode 10 is formed of a carbon material, excessive evaporation of carbon is suppressed, and the surface (surface layer) of the CNT where the excessively evaporated carbon is generated as impurities (for example, amorphous carbon or the like). Adhesion is suppressed and the life of the carbon anode itself is extended by suppressing consumption of the carbon anode itself.
On the other hand, when the anode 10 is formed of a metal material (carbon ions or the like are supplied from an atmospheric gas or a carbon cathode), the consumption of the metal anode itself is similarly suppressed and the life is extended.
The anode cooling means 50 may be slidable on the outer periphery of the anode 10 so that the anode cooling means 50 is always located at a fixed distance from the tip of the anode even when the anode 10 is worn. When the consumption of the anode 10 is small, the anode cooling means 50 may be disposed inside the anode 10. Further, the CNT manufacturing apparatus 2 may be housed in the chamber 30 according to the CNT manufacturing apparatus 1.
[0022]
(CNT production equipment 3-preheating cathode)
FIG. 3 is a schematic diagram illustrating Example 3 (hereinafter, referred to as CNT manufacturing apparatus 3) of the CNT manufacturing apparatus in the method of manufacturing CNT generated by arc discharge according to Embodiment 1 of the present invention. In FIG. 3, 3 is a CNT manufacturing apparatus, 50 is an anode cooling means, and 60 is a cathode preheating means. The same parts as those in FIG. 1 or FIG. 2 are denoted by the same reference numerals, and a part of the description will be omitted.
Cathode heating means 60 is, for example, a YAG laser, and preheats or heats an arc discharge generating portion on surface 21 of cathode 20 by laser irradiation. That is, since the arc discharge generating portion of the cathode 20 is preheated, an arc discharge is generated in the preheated region, and it is considered that conditions under which CNTs are easily grown are formed. As a result, the amount of CNT generated increases. I do.
Note that the cathode heating means 60 is not limited to laser heating, but may be any of high-frequency induction heating and the like. When the anode cooling means 50 is not provided, or the CNT manufacturing apparatus 3 may be housed in the chamber 30 according to the CNT manufacturing apparatus 1.
[0023]
(CNT production equipment 4-gas supply anode)
FIG. 4 is a schematic diagram showing Example 4 (hereinafter, referred to as CNT manufacturing apparatus 4) of the CNT manufacturing apparatus in the method for manufacturing CNT generated by arc discharge according to Embodiment 1 of the present invention. In FIG. 4, reference numeral 4 denotes a CNT manufacturing apparatus, 11 denotes a cylindrical anode, and 12 denotes a through hole of the anode. The same parts as those in FIG. 1 are denoted by the same reference numerals, and a part of the description will be omitted.
In FIG. 4, the discharge gas is blown from a through hole 12 of a cylindrical anode 11 toward an arc discharge generating portion. Conditions for easily generating an arc in the ejection path by ejection of the discharge gas are formed. In other words, a condition where the ionization degree of the discharged discharge gas is increased and a DC arc is easily generated in the gas discharge path is formed, or a stable anode point is formed on the inner surface of the through hole 12 in contact with the discharge gas. It is thought that it is formed.
[0024]
For this reason, the DC arc generation path is restricted, and irregular movement of the cathode point of the DC arc on the cathode electrode is prevented. As a result, at the position where the fixed cathode spot is generated (at the center of the DC arc), conditions for generating CNT are established, and CNT is generated. In other words, at the position where the fixed cathode spot is generated (the center of the DC arc), the condition for once-formed CNT generation is maintained, so that impurities such as amorphous carbon do not deposit at this position. Therefore, the collection rate of CNT can be increased. Further, an anode rotating means for rotating the cylindrical anode 11 or an anode elevating means for elevating may be provided.
Note that the CNT manufacturing apparatus 4 may be housed in the chamber 30.
Further, the cylindrical anode 11 may be used in any of the manufacturing apparatuses 1 to 3.
[0025]
(CNT production equipment 5-Anode with nozzle)
FIG. 5 is a schematic diagram showing Example 5 of the CNT manufacturing apparatus (hereinafter, referred to as CNT manufacturing apparatus 5) in the method for manufacturing CNTs generated by arc discharge according to Embodiment 1 of the present invention. In FIG. 5, 5 is a CNT manufacturing apparatus, 10 is an anode, and 70 is a discharge gas nozzle installed on the outer surface of the anode 10. The same parts as those in FIG. 1 are denoted by the same reference numerals, and a part of the description will be omitted.
That is, in FIG. 5, the discharge gas is blown from the discharge gas nozzle 70 along the outer surface of the anode 10 toward the arc discharge generating portion. Therefore, similarly to the CNT manufacturing apparatus 4 (FIG. 4), a condition is formed in which arc is easily generated in the ejection path by ejection of the discharge gas. In other words, since the degree of ionization of the discharged discharge gas is increased and a condition in which a DC arc is easily generated in the gas discharge path is formed, the DC arc generation path is restricted, and the cathode point of the DC arc on the cathode electrode is reduced. Irregular movement is prevented. Therefore, the collection rate of CNT can be increased.
The CNT manufacturing apparatus 5 may be housed in the chamber 30.
Further, the anode 11 with a nozzle may be used in any of the manufacturing apparatuses 1 to 3.
[0026]
(CNT production equipment 6-moving anode)
FIG. 6 is a schematic diagram showing Example 6 (hereinafter, referred to as CNT manufacturing apparatus 6) of the CNT manufacturing apparatus in the method for manufacturing CNT generated by arc discharge according to Embodiment 1 of the present invention. In FIG. 6, 6 is a CNT manufacturing apparatus, 10 is an anode, 20 is a flat cathode, and 80 is an anode moving mechanism for moving the anode 10. The same parts as those in FIG. 2 are denoted by the same reference numerals, and a part of the description will be omitted.
The anode moving mechanism 80 includes a traveling rail 81 disposed substantially parallel to the cathode 20, a traveling carriage 83 (equipped with traveling wheels 82) capable of traveling on the traveling rail 81, and a traveling rail on the traveling carriage 83. 81, a traversing rail 84, a traversing truck 86 (having traversing wheels 85) that can traverse on the traversing rail 84, and control means (not shown). Is installed.
[0027]
Therefore, since the anode 10 is relatively movable with respect to the cathode 20, the cathode deposit T21 is formed in a strip shape, that is, the tape-shaped (long foil having a predetermined width) CNT is collected. Becomes possible. Instead of the anode moving mechanism 80 for moving the anode 10, a similar moving mechanism may be installed on the cathode 20 to make the cathode 20 movable. The manner of the relative movement is not limited to a continuous substantially self-character shape, a substantially circular or rectangular spiral shape, or the like.
At this time, the anode 10 is not limited to being perpendicular to the surface 21 of the cathode 20, but may be inclined at a predetermined angle.
Note that any one of the CNT manufacturing apparatuses 1 to 5 may be applied to the CNT manufacturing apparatus 6. That is, the chamber 30 may be provided, the anode cooling means 50 may be provided, the cathode heating means 60 may be provided, the discharge gas nozzle 70 may be provided, or the anode 10 may be replaced with the cylindrical anode 11. Further, an anode rotating means for rotating the anode 10 or the cylindrical anode 11 or an anode elevating means for elevating may be provided.
[0028]
(CNT production equipment 7-rotating cathode)
FIG. 7 is a schematic diagram showing Example 7 of the CNT manufacturing apparatus (hereinafter, referred to as CNT manufacturing apparatus 7) in the method for manufacturing CNTs generated by arc discharge according to Embodiment 1 of the present invention. 7, reference numeral 7 denotes a CNT manufacturing apparatus, 10 denotes an anode, 23 denotes a cylindrical or cylindrical rotating cathode, and 90 denotes a negative anode moving mechanism capable of relatively moving the anode 10 and the rotating cathode 23. 2 and 3 are denoted by the same reference numerals, and a part of the description will be omitted.
The negative anode moving mechanism 90 includes a moving rail 91 disposed substantially parallel to the rotation axis of the rotating cathode 23, a moving truck 93 (having moving wheels 92) movable on the moving rail 91, A cathode rotating mechanism 94 for rotating the rotating member 23 and control means (not shown) are provided.
[0029]
Therefore, since the anode 10 is movable in the direction of its rotation axis with respect to the rotating cathode 23, the cathode deposit T21 (not shown) is formed in a belt shape, that is, a tape shape (length having a predetermined width). It is possible to collect the CNTs of the scale foil).
Then, since the rotating cathode 23 rotates in synchronization with the movement of the anode 10, the shape of the tape is, for example, helical, substantially annular, and the rotating cathode 23 immediately before the end point of the ring is connected to the starting point of the ring. After rotating along the entire length of the rotating cathode 23 in the direction of the rotating axis (forward path), the rotating cathode 23 is slightly rotated. There are various shapes such as a continuous substantially self-shaped character which is moved in the opposite direction (return) again.
[0030]
At this time, the anode 10 is not limited to the one perpendicular to the surface 21 of the rotating cathode 23 (radial from the rotation axis), but may be inclined at a predetermined angle (offset in the radiation direction from the rotation axis). Good.
Note that any one of the CNT manufacturing apparatuses 1 to 5 may be applied to the CNT manufacturing apparatus 7. That is, the chamber 30 may be provided, the anode cooling means 50 may be provided, the cathode heating means 60 may be provided, the discharge gas nozzle 70 may be provided, or the anode 10 may be replaced with the cylindrical anode 11. Further, an anode rotating means for rotating the anode 10 or the cylindrical anode 11 or an anode elevating means for elevating may be provided.
[0031]
[Embodiment 2]
(Electrode material 1-carbon cathode)
Conventionally, CNTs generated by arc discharge are mainly composed of CNTs (particularly, multilayer CNTs), in which carbon vapor and carbon ions generated from a carbon anode diffuse to the cathode side and condense on the cathode surface (the temperature is lower than the anode). Was thought to be synthesized.
However, according to the experiment of the present inventor, even if only the carbon vapor and the carbon ions from the anode were increased, a large amount of the graphitic carbon powder or the amorphous carbon powder adhered to the cathode surface. It has been found that the percentage of CNT contained in the deposited sediment is rather reduced.
Then, as a result of repeating various experiments, the inventor of the present application focused on the cathode as an important factor for increasing the CNT collection rate, and obtained the following knowledge.
[0032]
A carbon material for a cathode used for synthesizing CNTs generated by arc discharge is generally manufactured in the following steps, and its structure, structure, and mechanical properties depend on the raw materials, manufacturing method, and heat treatment temperature during manufacturing. Characteristics and physical properties differ greatly. That is,
{Circle around (1)} Various petroleum or coal-based coke powders and the like are used as raw carbonaceous powders, and various pitches such as coal tar pitch and petroleum-based pitch are used as a binder and mixed and stirred.
{Circle around (2)} The organic material thus obtained is formed by a method such as molding, extrusion, CIP formation,
{Circle around (3)} In general, the firing treatment is performed at a temperature of 1500 ° C. or less. At this point, the raw material organic matter has almost completed polycondensation and is in a carbonized state.
{Circle around (4)} After that, if necessary, various pitches are impregnated, and re-heat treatment is performed, and if necessary, graphitization heat treatment is performed at a temperature of 3000 ° C. or lower. In this way, a carbon material having required mechanical performance and physical properties has been manufactured.
[0033]
First, paying attention to the heat treatment temperature at the time of production, arc discharge was performed using various carbon materials having different heat treatment temperatures as the cathode material, and the amount of synthesized CNTs was compared. It has been found that many CNTs can be synthesized using a carbon material. That is, the present inventors have found that a carbon material made of carbon in which graphitization of carbon has hardly progressed (so-called “carbonaceous”) is suitable for the cathode.
[0034]
[Table 1]

[0035]
Table 1 compares the CNT collection status when the carbon material used for the cathode is changed (when the carbonaceous condition is changed). The arc discharge conditions are as follows:
(1) Carbon cathode: material is variously changed with a rod-like carbon material having a diameter of 36 mm (A to G),
(2) Anode: rod-shaped carbon anode having a diameter of 10 mm,
(3) Discharge gas: Ar gas (supplied to the anode discharge generating section),
(4) Atmospheric gas: an atmospheric atmosphere.
[0036]
In Table 1, when carbon materials A, F, and G were used as cathodes, many CNTs were produced with high purity (high collection rate). All of these were carbonaceous materials, and the heat treatment temperature during production was 1000 ° C. to 1500 ° C., which proved that such heat treatment temperature was suitable.
Since the specific resistance values of the carbon materials A, F and G were 5900 μΩ · cm, 4600 μΩ · cm and 11000 μΩ · cm, the specific resistance value of the cathode carbon material was larger than 3500 μΩ · cm, preferably 4000 μΩ · cm. cm or more.
Furthermore, since the thermal conductivity of the carbon materials A, F and G was 23 W / mK, 31 W / mK and 20 W / mK, respectively, the thermal conductivity of the cathode carbon material was smaller than 52 W / mK, preferably 40 W / mK. It can be seen that it is sufficient if it is less than mK.
[0037]
On the other hand, when carbon materials B, C, D and E were used as cathodes, the CNT purity (collection rate) was low and the yield (collection amount) was low. These were all made of graphite or a mixture of graphite and carbon.
The specific resistance value of the carbon material E was 3500 μΩ · cm.
Further, the thermal conductivity of the cathode carbon material E was 52 W / mK.
[0038]
In the above experiment, the material of the anode carbon material was changed. However, since the material and the purity of the CNT were hardly affected, the material of the cathode carbon material greatly affected the yield and the purity of the CNT. It could be confirmed.
From the above, (1) a carbon material made of carbonaceous material obtained by setting the heat treatment temperature at the time of production from 1000 ° C. to 1500 ° C., (2) a carbon material having an electric resistance value of 4000 μΩ · cm or less, or (3) ▼ High-purity CNTs can be generated by using a carbon material having a thermal conductivity of 40 W / mK or less as a cathode.
However, even if the heat treatment temperature during the production is not in the range of 1000 ° C. to 1500 ° C., the electric resistance value is 4000 μΩ · cm or more and the thermal conductivity is 40 W / It has been found that any carbon material having a mK or less may be used.
[0039]
8 and 9 are thermoviewer photographs showing the results of the temperature measurement of the arc discharge part in the CNT manufacturing apparatus 2 (cooling anode, see FIG. 2), which are for carbon material F and carbon material D, respectively. Since the high-temperature region is wide in the arc discharge part of the cathode using the carbon material F (having a low proportion of graphitization and made of carbonaceous material), the temperature of the discharge part of the carbon cathode is an important factor for CNT generation. Was found to be related.
That is, the carbon material F is a carbonaceous material having a relatively low heat treatment temperature and a low degree of graphitization (crystallization), and therefore has a high electric resistance value (specific resistance) and a low thermal conductivity.
For this reason, the arc generating portion (same as the cathode spot) of the cathode has a high current density and is heated to a high temperature by a large electric resistance heat generation. In addition, since heat is difficult to escape due to the low thermal conductivity, heat is trapped in a narrow range near the cathode point, and the heat is further increased. At this time, it is considered that the temperature of the cathode is a temperature condition under which CNT is easily generated.
[0040]
(Electrode material 2-Cathode cathode)
The electrode material used for the cathode may be the carbon material itself (such as the carbon material F) or may be a mixed material obtained by mixing a catalyst material such as Ni having a catalytic action of CNT synthesis with the carbon material. . The catalyst material may be any of metals such as Co, Fe and Pt and metal compounds such as Ni-Co and Fe-Ni in addition to Ni. Further, a mixture of two or more of the metal and the metal compound may be used.
Further, even if fine particles of a catalytic substance (for example, Ni fine particles) are adhered to the surface of the carbon material by a binder instead of the mixed material, the catalytic substance is chemically vacuum-deposited (CVD) or physically vacuum-deposited (ionized). Physical vacuum deposition using a target made of a mixture of fine particles of catalyst material and carbon particles, even if plating and mixing a mixture of fine particles of catalyst material, carbon particles, and a binder. May be.
[0041]
That is, since the cathode is used as a supply source of the catalyst material, a small amount of the catalyst material is evaporated by the arc heat in the vicinity of the generation region (near the cathode point of the DC arc), and the nano-level ultrafine particles of the catalyst material ( (Smaller than the particle size of the mixed catalyst material) is generated in the generation region. Since the ultrafine catalyst material effectively acts as a catalyst, most of it functions as a catalyst, and only a necessary amount evaporates, so that useless consumption of the catalyst material is eliminated.
At the same time, since the evaporated catalyst material does not grow into oversized particles, the oversized catalyst material does not mix with the CNTs (accumulate on the CNTs once generated).
[0042]
Furthermore, since a DC arc is generated from the anode to the cathode, when a catalyst substance is supplied from the anode, catalyst particles grow large in the DC arc and the DC arc is easily disturbed, as in the present invention. When the catalyst material is supplied from the cathode (even when the particle size of the catalyst material mixed in the cathode is large), stable DC arc discharge occurs without disturbance of the DC arc.
[0043]
(Electrode material 3-catalyst anode)
The electrode material used for the anode may be a carbon material obtained by press-molding and sintering particles of graphitizable carbon, or the carbon material itself (such as carbon material F). There is a case where a mixed material is obtained by mixing a catalyst substance such as Ni having a synthetic catalytic action. The catalyst material may be any of metals such as Co, Fe and Pt and metal compounds such as Ni-Co and Fe-Ni in addition to Ni. Further, a mixture of two or more of the metal and the metal compound may be used.
[0044]
(Electrode material 4-metal anode)
When carbon vapor or carbon ions are supplied from an atmospheric gas or a carbon cathode, the anode can be formed of a metal material such as copper or a copper alloy instead of the carbon material. At this time, since the anode is hardly consumed, the distance between the electrodes is easily controlled, and stable arc discharge can be obtained.
Furthermore, in the case of a metal anode, the supply amount of carbon vapor or carbon ions can be controlled independently of other parameters, so that an extra carbon raw material is not required, and reduction of the raw material is achieved.
[0045]
That is, in the case of a carbon anode, the carbon supplied from the carbon anode side is considered to be gaseous carbon which is mainly sublimated by the carbon anode heated by the arc heat, and the sublimation amount is the arc heat (arc current, voltage , Which varies depending on the atmosphere) and the heat capacity (which varies depending on the shape) of the carbon anode. In addition, such an amount of sublimation is considered to be overwhelmingly larger than the amount required for CNT generation.
[0046]
[Embodiment 3]
(CNT production method 1-fixed solid anode)
FIG. 10 shows Example 1 of the CNT manufacturing method according to Embodiment 3 of the present invention (hereinafter, referred to as CNT manufacturing method 1), which is an arc in a CNT manufacturing apparatus 1 (fixed solid anode, see FIG. 1). It is a schematic diagram which shows a discharge situation (general discharge). The discharge conditions in FIG. 10 are as follows.
(1) Cathode 20: plate-like carbon material (resistance value 3500 μΩ · cm)
(2) Anode 10: rod-like carbon material
(3) Discharge gas: Ar gas (supplied to the arc discharge generating section)
(4) Atmospheric gas: Atmospheric atmosphere
[0047]
At this time, the position at which the arc discharge occurs largely moves around, and the position of the cathode point moves violently and irregularly on the cathode surface 21 (in FIG. 10, the arc A1 generated at a certain time differs from the arc A1 generated at a different time). Arc A2 is illustrated in an overlapping manner). A3 is a cathode jet, which is a portion where carbon in the cathode is evaporated and some carbon atoms are ionized.
Such a violent and irregular movement of the arc is particularly remarkable in an argon gas atmosphere under atmospheric pressure, but a similar movement is observed in a helium gas or hydrogen gas atmosphere under a low pressure.
[0048]
FIG. 11 is a scanning electron microscope (SEM) photograph showing a result of observing a cathode spot when an arc is generated for a short time by the general discharge of FIG. FIG. 11A is an SEM photograph showing the center of the cathode spot and its periphery, FIG. 11B is an enlarged SEM picture of the center of the cathode spot, and FIG. 11C is an enlarged SEM picture of the periphery of the cathode spot.
As is clear from these SEM photographs, CNTs are densely formed at the center of the cathode spot, whereas a lump of amorphous carbon (amorphous carbon) is deposited around the center of the cathode spot. It is only. In other words, it is understood that the conditions for synthesizing the CNTs are satisfied at the cathode point of the arc, but the conditions for not synthesizing the CNTs in the surrounding area.
From these results, it is considered that in a general arc discharge mode in which the cathode spot moves strongly and irregularly, the conditions under which CNTs are synthesized on the cathode surface 21 and the conditions under which CNTs are not synthesized are alternately repeated.
[0049]
(CNT production method 2-cooling anode)
Example 2 (hereinafter referred to as CNT manufacturing method 2) of the method for manufacturing CNTs according to Embodiment 3 of the present invention is a method for manufacturing CNTs using a CNT manufacturing apparatus 2 (cooling anode, see FIG. 2). However, since it is the same as the CNT manufacturing method 1 (fixed solid anode), the description is omitted.
[0050]
(CNT production method 3-preheating cathode)
FIG. 12 shows Example 3 (hereinafter referred to as CNT manufacturing method 3) of the CNT manufacturing method according to Embodiment 3 of the present invention. It is an enlarged photograph of a cathode spot center part. That is, under the following production conditions, the distance between the plate-shaped carbon cathode 20 and the rod-shaped carbon anode 10 was appropriately set, and current was supplied from the arc discharge power supply 40 to perform arc discharge for one second. At this time, the laser output was changed, and the heating temperature of the surface 21 of the plate-like carbon cathode 20 and the amount of generated CNT were observed.
(1) Cathode 20: plate-like carbon material (resistance value 600 μΩ · cm)
(2) Anode 10: rod-like carbon material
(3) Discharge gas: Ar gas (supplied to the arc discharge generating section)
(4) Atmospheric gas: Atmospheric atmosphere
(5) Cathode heating means 60: YAG laser (adjusted so that the beam irradiation diameter is substantially equal to the diameter of the discharge generating portion on cathode surface 21)
(6) Anode cooling means 50: water-cooled copper
[0051]
In FIG. 12, when no preheating was performed, no CNT was generated. It can be seen that the CNTs preheated to 500 ° C. have CNTs formed all over the surface. In addition, it can be seen that CNTs are pre-heated to 2000 ° C., CNTs are generated all over the surface, and CNT fibers are growing long.
On the other hand, no CNT was observed in the sample preheated to 2500 ° C. This is partly because the cathode surface 21 is overheated because it is preheated to 2500 ° C. and heat is generated by arc discharge, and the conditions for generating CNTs are not met, or the CNTs once generated are sublimated or decomposed. Presumed.
This indicates that the generation of CNT is affected by the preheating temperature of the cathode, and that the preheating temperature is preferably set to 500 ° C. to 2000 ° C.
[0052]
(CNT production method 4-gas supply anode)
FIGS. 13 and 14 show Example 4 of the CNT manufacturing method according to Embodiment 3 of the present invention (hereinafter, referred to as CNT manufacturing method 4), and CNT manufacturing apparatus 4 (gas supply anode, see FIG. 4). 4A and 4B are a schematic diagram showing an arc discharge situation in FIG. 5A and a scanning electron microscope (SEM) photograph showing generated CNTs. The CNTs are located at the center of the cathode deposit, and it can be seen that high-purity multilayer CNTs have been synthesized. The generation conditions are as follows.
(1) Cathode 20: plate-like carbon material (resistance value 4600 μΩ · cm)
(2) Cylindrical anode 11: cylindrical carbon material having an outer diameter of 36 mm and an inner diameter of 10 mm
(3) Discharge gas: Ar gas (supplied to the arc discharge generating section)
(4) Atmosphere: open space, that is, atmospheric atmosphere under atmospheric pressure
(5) Discharge gas: argon gas containing 3% hydrogen, flow rate of 10 l / min (blows out from the through-hole 12 of the cylindrical anode 11 toward the cathode 20)
(6) Arc discharge: arc discharge for 1 minute at a current of 500 A and a voltage of 35 V (arc length about 5 mm).
[0053]
That is, since the discharge gas is blown out from the cylindrical electrode 11, the arc A4 is generated along the flow path of the discharge gas, and the cathode point is generated at a position always facing the discharge gas outlet. Since the arc is stabilized (the cathode spot is fixed) for a long time, high-purity CNTs are synthesized at the cathode spot of the arc discharge (the same as the center of the cathode deposit).
[0054]
This is considered to be because the inner surface of the through-hole 12 of the cylindrical electrode 11 is in contact with the discharge gas, so that an anode point is easily formed stably here.
In addition, since an inert gas such as argon has a high ionization efficiency due to collision with electrons and provides a space in which an arc A4 is easily generated, a discharge blown out from the through hole 12 of the cylindrical electrode 11 toward the cathode 20 is provided. It is considered that the use gas restricts the generation path of the arc A4.
Therefore, if the arc A4 is generated after the supply of the discharge gas from the through hole 12 of the cylindrical electrode 11 to the cathode 20 is started, the arc generation path is restricted from the initial generation of the arc A4. Thus, irregular movement of the cathode spot can be prevented, so that the conditions for forming CNTs formed at the cathode spot are maintained, and high-purity CNTs are deposited here.
[0055]
The discharge gas supplied from the through-hole 12 of the cylindrical electrode 11 is (1) pure argon, or (2) an argon gas mixed with about 20% or less of hydrogen gas, and (3) about 20% or less. Ar gas mixed with hydrogen gas or helium gas may be used.
In particular, when hydrogen gas was mixed with argon at several percent to several tens percent, the CNT yield could be increased without impairing the stability of the arc. This is considered to be because hydrogen gas has an effect of converging the arc, and increases the arc temperature or the current density on the cathode surface, which is a condition under which CNT is easily generated.
[0056]
FIG. 15 shows the relationship between the cross-sectional area of the through-hole of the tubular electrode, the flow rate of the supplied (same as blowing out) discharge gas, and the arc generation mode in the CNT manufacturing apparatus 4 (gas supply anode, see FIG. 4). It is a graph of an experimental result. In FIG. 15, the flow rate of the discharge gas (pure argon or argon gas mixed with hydrogen gas or helium gas of about 20% or less) is 1 mm in sectional area of the through hole 12. ^Two If it is less than 10 ml / min, it will not function sufficiently as a plasma gas, and the flow rate will be 1 mm in cross-sectional area of the hole 11a. ^Two If it is more than 400 ml / min, the concentration of the plasma gas increases to the peripheral portion of the electrode, so that arc discharge is likely to occur not only in the central portion but also in the peripheral portion, and the arc cannot be concentrated.
That is, the flow rate of the discharge gas is set to 1 mm ^Two By setting the flow rate to 10 to 400 ml / min, it is possible to create a condition in which arc discharge is more likely to occur only in the central portion of the cylindrical anode 11 than in the peripheral portion while functioning as a plasma gas. Therefore, since the cathode spot is fixed, CNT with high purity can be recovered with a high yield.
[0057]
FIG. 16 illustrates the cross-sectional area of the through-hole of the cylindrical electrode and the situation where the catalyst powder is mixed in the supplied (same as blow-out) discharge gas in the CNT manufacturing apparatus 4 (gas supply anode, see FIG. 4). It is a schematic diagram. The same parts as those in FIG. 4 are denoted by the same reference numerals, and a part of the description will be omitted.
That is, the through hole 12 of the cylindrical anode 11 communicates with the catalyst mixing container 71. Then, the discharge gas and the catalyst material M1 are mixed and sprayed toward the cathode 20 in a catalyst-mixed container 71 containing a metal powder or a metal compound powder M1 (hereinafter, referred to as a catalyst material M1) serving as a catalyst. ing. That is, the catalyst material M1 is supplied to the arc generating portion on the discharge gas.
[0058]
At this time, the ionization degree of the discharge gas is increased at a high temperature due to the arc discharge, and the conductivity is increased as compared with the peripheral portion. Therefore, the anode point of the cylindrical electrode 11 is formed stably, and the path of the discharge gas is formed. Along which the arc A4 is generated (same as fixing the cathode spot). Further, the catalyst substance M1 mixed in the discharge gas is super-finely divided by the arc heat, and acts to generate single-layer CNT. That is, high-purity single-walled CNTs can be recovered from the fixed cathode spot and the cathode deposits around the fixed cathode spot.
[0059]
(CNT production method 5-Anode with nozzle)
In Example 5 of the CNT manufacturing method according to Embodiment 3 of the present invention (hereinafter, referred to as CNT manufacturing method 5), a CNT manufacturing apparatus (discharge gas is blown out from an attached discharge gas nozzle, CNT is manufactured according to FIG. 5). Also in this case, similarly to the CNT manufacturing method 4 (discharging gas is blown out from the through-hole of the cylindrical electrode), the fixation of the cathode spot was observed, and the fixed cathode spot and the cathode deposit on the periphery thereof were fixed. , High-purity single-walled CNTs have been recovered.
The generation situation is the same as that of the above-mentioned CNT manufacturing method 4 (gas supply anode), and the description is omitted.
[0060]
(CNT production method 6-moving gas supply anode)
FIG. 17 shows Example 6 (hereinafter, referred to as CNT manufacturing method 6) of the CNT manufacturing method according to Embodiment 3 of the present invention, which is performed in a CNT manufacturing apparatus 6 (moving anode, see FIGS. 4 and 6). It is a schematic diagram which shows the generated CNT. The generation conditions are as follows.
(1) Cathode 20: plate-like carbon material (resistance value 3500 μΩ · cm)
(2) Cylindrical anode 11: cylindrical carbon material having an outer diameter of 10 mm and an inner diameter of 4 mm
(3) Atmosphere: open space, that is, atmospheric atmosphere under atmospheric pressure
(4) Discharge gas: argon gas containing 3% hydrogen, flow rate of 1 liter / minute (blows out from the through hole 12 of the cylindrical anode 11 toward the cathode 20)
(5) Arc discharge: arc discharge for 1 minute at a current of 100 A and a voltage of 20 V (arc length about 1 mm).
(6) Anode movement: 10 cm / min
[0061]
That is, as a result of performing arc discharge while moving the cylindrical electrode 11 in one direction, a cathode volume adhering to the cathode surface 21 in a strip shape was generated. The cathode volume is composed of a tape-shaped substance C21 whose center part (corresponding to a path scanned by the center part (cathode point) of the arc A4) is spontaneously stripped, and an adhering substance T23 adhering to the cathode surface 21 on both sides thereof. It is configured.
Observation of the tape-like substance C21 with a scanning electron microscope (SEM) and a transmission electron microscope (TEM) revealed that the tape-like substance C21 was composed of an aggregate of high-purity CNTs (hereinafter, a high-purity CNT tape or CNT). Tape). Further, the adhered substance T23 was amorphous carbon.
[0062]
FIG. 18 is a schematic diagram in which a production mechanism (production mechanism) of a high-purity CNT tape in production method 6 (moving gas supply anode) is estimated. The CNT generation mechanism is the same as that of the static arc (CNT manufacturing method 4—gas supply anode, see FIG. 16). That is, CNT is generated at the center of the arc A4, and amorphous carbon is deposited around the CNT.
[0063]
Therefore, when the anode is moved (hereinafter, sometimes referred to as a moving arc), the condition under which CNTs are likely to be generated is moved together with the movement of the arc A4. For this reason, when the arc A4 approaches, the amorphous carbon T23 accumulates around the arc A4, and when the arc A4 arrives there, the condition that the CNT is easily generated on the already deposited amorphous carbon T23 (arc A4) Is formed at the center of the CNT), so that CNT is generated thereon. Furthermore, when the center of the arc A4 leaves, the conditions under which CNTs are easily generated at the position of the generated CNTs collapse, and amorphous carbon T23 is deposited on the generated CNTs.
Therefore, the CNTs are formed in a tape shape in which the upper, lower, left, and right sides are surrounded by the amorphous carbon T23 (see the upper part (a) of FIG. 18).
[0064]
However, after the arc A4 has passed, the amorphous carbon T23 on the upper surface comes into contact with the atmosphere in a high-temperature state, so that it is oxidized and burned, and partly burns off (middle in FIG. 18) (b)).
[0065]
Further, it is considered that when the temperature of the cathode deposit becomes low, a phenomenon in which the CNT tape C21 peels off in a tape shape occurs due to a difference in thermal expansion coefficient between the CNT tape C21 and the amorphous carbon T23 (lower part (c) in FIG. 18). Can be
That is, high-purity CNTs are generated by fixing the cathode spot by the arc discharge of the cylindrical electrode 11, and by moving the cylindrical electrode 11, high-purity CNTs can be formed in a tape shape. Is spontaneously exfoliated, so that such a high-purity CNT tape can be easily recovered in a high yield.
[0066]
(2-moving gas supply anode and heated cathode in CNT production method 6)
FIG. 19 is an electron micrograph showing a high-purity CNT tape produced by CNT production method 6-2 produced by employing a heated cathode in the CNT production apparatus 6 (moving gas supply anode). The generation conditions are as follows.
(1) Carbon cathode 1: flat carbon material
(2) Anode 3: rod-shaped carbon material
(3) Discharge gas: Ar gas (supplied to the anode discharge generating section)
(4) Atmospheric gas: Atmospheric atmosphere
(5) Cathode heating means: high-frequency induction heating device (interval with carbon cathode: 4 mm)
(6) Anode cooling means: water-cooled copper
(7) Truck 19 moving speed: 10 cm / min
[0067]
When heating was performed with the oscillation frequency of the high-frequency induction heating device set to 10 kHz under the above conditions, the cathode temperature rose to 800 ° C. only by the high-frequency induction heating. In this state, when an Ar gas is injected into the discharge space from the discharge gas supply device to generate an arc discharge between the anode and the cathode, a high-density and high-purity CNT tape is generated.
Although the discharge time in the atmosphere was set to 5 minutes, when the anode was not cooled, the exhaustion was severe and continuous discharge for 2 minutes or more was impossible. On the other hand, the water-cooled anode was slightly consumed immediately after the start of the discharge, but the consumption was reduced thereafter and the discharge was possible for a long time.
[0068]
When the anode is cooled, the amount of impurities adhering to the surface of the collected CNT tape is smaller than when the anode is not cooled, so that most of the carbon impurities in the cathode deposits are flying from the anode. Is estimated. Therefore, by cooling the anode, it is possible to suppress unnecessary anode consumption and to suppress the accumulation of scattered matter from the anode, which becomes carbon impurities in the cathode deposit, and to prolong the life of the anode. It was proved that it could be achieved.
[0069]
(CNT production method 7-rotating cathode)
FIG. 20 shows Example 7 (hereinafter referred to as CNT manufacturing method 7) of the CNT manufacturing method according to Embodiment 3 of the present invention, and shows the arc discharge state in CNT manufacturing apparatus 7 (rotating cathode, see FIG. 7). FIG. The discharge conditions in FIG. 20 are as follows.
(1) Rotating cathode 23: a columnar carbon material having a diameter of 35 mm, a rotation speed of 1.5 rotations / minute
(2) Cylindrical anode 11: hollow carbon electrode having an outer diameter of 10 mm and an inner diameter of 4 mm, moving speed of 35 mm / min
(3) Discharge gas: pure argon gas, flow rate is 1 liter / minute
(4) Atmospheric gas: under atmospheric pressure / atmospheric atmosphere
(5) Discharge conditions: current 100A, voltage 20V (arc length about 1mm)
That is, the rotating cathode 23 was rotated, and the cylindrical electrode 11 was moved linearly in the axial direction of the rotating cathode 23 to move the cathode spot in a spiral on the rotating cathode.
[0070]
As a result, a high-purity CNT tape which was a band-like foil having a width of about 2 to 3 mm and a thickness of about 100 μm was produced. The width and thickness of the CNT tape can be changed according to the shape, size and production conditions of the electrode. In the present invention, those that have not been subjected to a purification treatment (heating or the like) are referred to as “unpurified CNTs”.
[0071]
21 and 22 show an appearance photograph and an SEM photograph of the high-purity CNT tape produced respectively. Spherical amorphous carbon of about 10 nm adheres to the tape surface, but the inside is composed of a high-purity CNT aggregate. Note that this amount of amorphous carbon can be easily removed by heat treatment (another step) in an oxidizing atmosphere.
[0072]
(2-moving gas supply anode and cooling gas spraying in CNT production method 7)
FIG. 23 is a schematic diagram showing an arc discharge state in CNT manufacturing method 7-2 in which a cooling gas blowing means is arranged in the CNT manufacturing apparatus 7 (rotating cathode). The discharge conditions in FIG. 23 are the same as those shown in FIG. The same parts as those in FIG. 20 are denoted by the same reference numerals, and a part of the description will be omitted.
That is, a cooling gas is blown from the gas nozzle 51 to the high-purity CNT tape C21 generated on the locus of the cathode point of the arc A4.
[0073]
After generation of the CNT tape C21, a cooling gas is blown to promote cooling, thereby promoting separation. The cooling gas is not limited, and any gas such as air and nitrogen can be used as long as it has a cooling effect.
Since the CNT tape C21 is formed in a thin film (strip-like foil) on the rotating cathode 23, when the CNT tape C21 is rapidly cooled by spraying a cooling gas, the CNT tape C21 is in contact with the surrounding amorphous carbon T23 and the rotating cathode 23. The separation is promoted by thermal stress acting between them.
[0074]
The oxygen contained in the cooling gas or the air entrained in the cooling gas causes amorphous carbon and the like (polycrystalline graphite and amorphous carbon foil-like pieces and particles) adhered to the CNT tape C21. Since the oxidation and combustion are promoted, the purity of the CNT tape C21 is increased, and the adhesion to the surface of the rotating cathode 23 is weakened, so that the separation is further facilitated.
[0075]
The adhesive force also varies depending on the surface roughness of the surface of the cathode material (for example, arithmetic average roughness (Ra)). That is, when the surface roughness of the cathode material is rough, the adhesive force is increased. For example, if the arithmetic average roughness (Ra) of the upper surface of the rotating cathode 23 is set to 3.2 μm or less, the adhesive force is weakened and spontaneous peeling occurs. , The collection of the CNT tape C21 becomes very easy.
[0076]
(3- Moving gas supply anode and cathode heating of CNT production method 7)
FIG. 24 is a schematic diagram showing an arc discharge state in CNT manufacturing method 7-3 in which a cathode heating means is arranged in the CNT manufacturing apparatus 7 (rotating cathode, see FIG. 20). The discharge conditions in FIG. 24 are the same as those shown in FIG. The same parts as those in FIG. 20 are denoted by the same reference numerals, and a part of the description will be omitted.
That is, the arc discharge is performed while the cathode point of the arc A4 or the forward portion of the arc A4 on the rotating cathode 23 in the traveling direction of the arc is heated by the laser beam from the laser oscillator 60.
[0077]
At this time, the temperature of the cathode spot was higher than that without preheating, and the CNT tape C21 having high purity could be collected.
Instead of the laser oscillator 60, the entire cathode may be preheated and heated by resistance heat generated by energization, or the surface of the rotating cathode may be preheated and heated by radiation from the surroundings.
As described above, the CNT manufacturing method is individually described in the third embodiment, but the present invention is not limited to this, and any one of the CNT manufacturing methods may be appropriately combined and implemented.
[0078]
[Embodiment 4]
FIGS. 25 and 26 are electron micrographs showing CNTs generated by arc discharge according to Embodiment 4 of the present invention. FIG. 25 (a) is an appearance photograph of a small piece of recovered CNT, and FIG. (B), (c) and (d) of FIG. 26 are the results of observing the surface (non-purified state) with an electron microscope.
The method for producing CNTs is based on the CNT production method 4 (gas supply anode), and the discharge conditions are as follows.
(1) Cathode 20: plate-like carbon material having a diameter of 20 mm and a thickness of 5 mm (resistance value 600 μΩ · cm)
(2) cylindrical anode 11: a carbon material having a diameter of 11 mm and an inner diameter of 4 mm
(3) Discharge gas: Ar gas, 0.5 to 5 l / min
(4) Atmospheric gas: Atmospheric atmosphere
(5) Discharge conditions: current 100A, voltage 20V, discharge time 0.1 to 1 second
[0079]
At this time, the cathode deposit is composed of CNTs deposited in a circular shape and amorphous carbon deposited in a ring shape around the CNTs, and the deposited diameter of the CNTs is 4 mm, which is almost equal to the size of the discharge generating portion of the arc discharge. Match. When the electrodes are relatively moved under the above conditions, a strip-shaped CNT tape having a width of 4 mm is obtained (described separately below).
When the deposited CNTs are observed by an electron microscope, it is found that long fibers having a considerable length with a smooth surface (hereinafter referred to as CNT fibers) are randomly and intricately entangled into a flocculent shape (hereinafter referred to as a CNT aggregate). Body).
[0080]
(CNT fiber)
Most of the CNT fibers constituting the CNT aggregate had a length of 10 μm or more, and some of the CNT fibers exceeded 20 μm. When a more detailed observation is performed, a small number is observed up to 50 μm or more or 100 μm.
When attention is paid to each CNT fiber, it has a linear shape near the end portion, but it is often seen to draw a continuous arc shape, and many have a radius of curvature of 1 to 10 μm. Of course, there is also a straight portion, that is, a portion having an infinite radius of curvature, while a portion having a radius of curvature of about 200 nm in a bent state is also observed.
[0081]
In addition, since the CNT fibers are not branched in the middle and the ends exposed on the surface extend linearly, it is confirmed that the CNT fibers are composed of the highly crystalline CNT fibers unique to the arc discharge method. Is done. Furthermore, since the CNT fibers draw a gentle arc at the place where they are entangled, it is observed that the CNT fibers are elastically deformed. Therefore, it is presumed that the CNT fibers have flexibility.
[0082]
FIG. 27 is a distribution diagram showing the measurement results of the thickness of the CNT fiber shown in FIG. 27, those having a diameter of about 5 to 10 nm occupy about 60%, and those having a diameter of about 15 nm or less occupy about 90%.
In addition, such a long CNT fiber (having high crystallinity as described later) can be generated using arc discharge. On the other hand, the vapor phase growth method (CVD method) and the laser ablation method cannot produce such long CNT fibers having high crystallinity, and a cotton-like aggregate in which such long fibers are entangled. I can't get it.
[0083]
(crystalline)
Conventionally, it has been difficult to produce long CNTs in which the structure of the graphene cylinder is good and each graphene cylinder can be clearly recognized. The fact that the structure of the graphene cylinder is good and that each graphene cylinder can be clearly recognized is generally expressed by the term “good crystallinity”.
It is generally said that CNTs having good crystallinity are generated by an arc discharge method. However, in the conventional arc discharge method, only long CNT fibers of about 1 μm can be generated.
[0084]
On the other hand, it is said that a long CNT can be generated by the vapor phase growth method (CVD method), but the long one has a diameter as large as 50 nm or more and has poor crystallinity. Such a CNT with poor crystallinity can be reformed into a crystal with good crystallinity by heat treatment. However, the reforming requires not only a heat treatment at a high temperature of about 3000 ° C. but also a heat treatment. However, it has been difficult to prevent a layered defect occurring at a certain probability in the length direction of the CNT. Further, in the heat treatment process, the length of the CNTs was shortened, and it was difficult to obtain CNTs with good crystallinity and as long as more than 10 μm.
[0085]
FIG. 28 is a schematic diagram illustrating crystallinity of CNT generated by arc discharge according to Embodiment 4 of the present invention. FIG. 28A schematically shows the state of the hexagonal mesh surface of the CNT side wall, and shows the state of the CNT by the arc method. The mesh plane is long in parallel with the fiber axis, and the graphene cylinder is clearly formed, and the lamination intervals are also uniform.
On the other hand, FIG. 28 (b) shows the structure of CNTs generated by the CVD method, in which small mesh planes are intermittently connected, and are oriented almost parallel to the fiber axis, but the spacing between the planes is small. It has been mixed.
[0086]
Originally, a crystal must have regularity in the arrangement of three-dimensional atoms and a predetermined regular relationship also in the direction of lamination of the mesh plane. Has no such relationship, and has a so-called turbostratic structure.
Therefore, it is different from graphite crystal in a strict sense. However, as shown in FIG. 3 (a), a net plane is long in parallel with the fiber axis and the lamination interval is also equal. Represents. As described above, the structure in which the mesh plane is connected to the fiber axis in parallel for a long time is a factor showing characteristics excellent in strength, heat conductivity, and conductivity.
[0087]
Further, (c) and (d) of FIG. 28 show layer-like defects which are likely to be generated when CNT generated by the CVD method is heat-treated. (C) shows the absence of the layer in the middle of the length direction, and (d) shows the difference of the layer in the middle of the length direction.
[0088]
The CNT according to the present invention has good crystallinity, is a long fibrous shape, and has higher purity, and thus can be formed with sufficient strength for use. That is, it can be formed as a thin film material having a width of millimeter size, can be easily handled, and can be easily used in a wide range of applications such as an electron emission source, a sensor, or a functional separation film.
[0089]
On the other hand, conventionally, since CNTs have good crystallinity and do not have long CNTs, they have been used by being mixed with a resin, a metal, or the like. Therefore, many CNTs have to be used. Further, it is difficult to form a film-like material having a millimeter size spread, and even if mixed with the same amount as long CNT, the characteristics are inferior in many points such as conductivity, strength, and thermal conductivity.
[0090]
(Dense and dense area of CNT aggregate)
In the CNT aggregate, a sparsely aggregated region and a densely aggregated region are observed, and the densely aggregated portion protrudes toward the open space side with respect to the other portions (projects). .
In the dense part, the long CNTs are nestling on the bundle, and the number of CNTs gradually decreases as approaching the tip. The number of CNTs at the tip is 10 or less, almost 5 or less, and one of them Some ending with CNT are also observed.
The interval between the densely gathered regions is in the range of 2 to 40 μm, but this interval varies depending on the generation conditions, and in the present embodiment, the intervals are uniformly distributed at an interval of 5 to 20 μm. When this is viewed as a rectangular parallelepiped with a visual field of 2 μm, the volume density (the ratio of the volume occupied by the CNT fibers per unit volume and is the same as the bulk density, which is also referred to as the volume density to avoid confusion with the bulk specific gravity) 1 / 5 or more areas When observed in more detail, there are 1/2 or more dense areas.
On the other hand, the sparsely gathered area, when viewed as a rectangular parallelepiped with a visual field of 2 μm, has a volume density of 1/100 or less. Area was observed.
[0091]
(impurities)
When the surface of the CNT aggregate is observed, it is observed that impurities having a small particle size or film-like impurities are attached.
The diameter of the granular impurities in a certain range is 100 nm or less, and as observed, most of them have a particle size of 50 nm or less, and their area occupies 1% or less of the entire visual field (that is, the purity of the CNT surface is 99% or less). %).
In addition, when the inside was exposed and observed by the method described later, the impurity was not found. Therefore, the overall purity of the CNT aggregate in this range is extremely high and is close to approximately 100%.
[0092]
In other ranges, film-like impurities account for 20% or more of the surface, and 70% or more of them. The impurity was substantially in the form of a film made of carbon, and the thickness was 100 nm to several μm in a thick portion, and was at most 20% or less in terms of weight with respect to the whole cathode deposit. Therefore, it can be said that the proportion (purity) of the CNT aggregate in the deposit is at least 80% or more.
[0093]
(CNT tape)
FIG. 29 is a transmission electron microscope photograph showing CNTs generated by the arc discharge according to Embodiment 4 of the present invention, in which the surface (non-refined state) is observed with a transmission electron microscope. The method of producing CNTs is based on the CNT production method 7 (rotating cathode), and the discharge conditions are as follows.
(1) Rotating cathode 23: cylindrical carbon material having a diameter of 36 mm, 0.5 to 3 rotations / minute
(2) cylindrical anode 11: a carbon material having a diameter of 10 mm and an inner diameter of 4 mm, moving in the axial direction of the cathode at 10 to 50 mm / min.
(3) Discharge gas: Ar gas, 0.5 to 5 l / min
(4) Atmospheric gas: Atmospheric atmosphere
(5) Discharge conditions: current 100A, voltage 20V
[0094]
The anode may be a water-cooled copper electrode. A cathode having a large resistivity, preferably 2000 μΩ · cm or more, more preferably 4000 μΩ · cm or more is suitable for forming a CNT aggregate. When the resistivity is low, a similar CNT aggregate can be obtained by performing arc discharge while preheating the cathode discharge generating portion (preferably in the range of 500 to 2000 ° C.).
As a result, the tape-like CNT aggregate is recovered, and in a non-refined state, the width is 1 to 10 mm, the thickness is 10 to 500 μm, and the length depends on production conditions and manufacturing equipment. Can be recovered. It should be noted that the arc discharge portion on the cathode surface is altered by the arc discharge.
[0095]
(Visual shape)
In FIG. 29, most of the CNT fibers constituting the CNT aggregate are multilayer CNTs (MWCNTs) having three or more graphene sheets. In addition, in a certain CNT fiber, the distance (contact interval) between the position where one CNT fiber is in contact and the position where the other CNT fiber is in contact is various, but at least 5 μm or more, and when observed in more detail, In some cases, the distance is 10 μm or more, and in some cases, the distance is 20 μm or more.
When a few seconds to a few minutes have passed since the arc passed, the foil-shaped aggregate may come off naturally from the surface of the rotating cathode, and even if it does not come off naturally, it can be easily peeled off by forced cooling etc. It is possible. Therefore, a CNT tape having an arbitrary length can be obtained. By dividing the CNT tape into a predetermined length or an arbitrary size, a CNT aggregate that can be used in various ways can be obtained.
[0096]
(Bulk specific gravity)
Further, since the mass of the CNT aggregate formed into a square sheet having a thickness of 50 μm and each side of 3 mm square is about 20 μg, the bulk specific gravity is 44 mg / cm. ^Three It is.
As will be apparent from observation with a transmission microscope described later, the fibers of the multilayer CNT are tubular (literally tubes) having a space inside, but the ratio of the space inside is very small. That is, when a specific multilayer CNT fiber is observed, the total volume of the graphene sheets forming the specific multilayer CNT fiber is approximately 70 to 90% with respect to the volume of the tube (same as the volume of the tube of the outermost layer). This is approximately 80%.
Therefore, when the volume density of the multilayer CNT fiber is 0.8, the specific gravity of graphite is 2.25 g / cm. ^Three Therefore, the specific gravity of the multilayer CNT fiber is 1.8 g / cm ^Three It becomes.
That is, 1 cm ^Three When the multilayer CNT fiber is solidly packed in the volume of 1.8 g, the mass is 1.8 g, whereas the actual CNT aggregate is 44 mg, so the volume density is 44 mg / 1.8 g = (1/41). .
However, this bulk specific gravity varies greatly, and can be made denser by compressing with an external force.
[0097]
(Emission characteristics)
Further, when the electron emission characteristics when the bulk specific gravity was changed by an external force were obtained, it was found that the electron emission characteristics became worse as the bulk specific gravity increased.
For example, 50 μA / mm ^Two To obtain the average electron emission density of
(1) Bulk specific gravity is 35mg / cm ^Three In the case of (corresponding to a volume density of 1/51), it is only necessary to apply a voltage for obtaining an average electric field strength of 6 to 7 kV / mm.
(2) Bulk specific gravity is 0.18 g / cm ^Three In the case of (corresponding to a volume density of 1/10), it is necessary to apply a voltage for obtaining an average electric field strength of about 8 kV / mm,
{Circle around (3)} Further, the bulk specific gravity is 0.9 g / cm. ^Three In the case of (corresponding to a volume density of ２), it is necessary to apply a voltage for obtaining an average electric field strength of 15 kV / mm.
[0098]
This is presumably because the surface is macroscopically smoothed by increasing the volume density, and the local electric field strength is reduced.
That is, the volume density is 1/10 or less (the bulk specific gravity is 0.18 g / cm ^Three In the following case, it has been found that a sufficient function as an electron emission source is exhibited.
On the other hand, when CNTs produced by a general arc discharge method are applied by purifying CNTs having an infinitely high purity, 50 μA / mm ^Two Since a voltage for obtaining an average electric field intensity of about 7 to 8 kV / mm is applied in order to obtain an average electron emission density of, the CNT aggregate according to the present invention can be said to have very good electron emission characteristics.
[0099]
In addition, while examining the electron emission source characteristics of the recovered CNT tape, some of them obtained a high average current emission density at a low applied voltage, but the diameter of constituent CNTs of this CNT aggregate was examined. However, CNTs having a diameter of 4 to 15 nm accounted for 50 to 80% of the whole.
Therefore, when the CNT aggregate according to the present invention is used as an electron emission source, it is only necessary to bond the CNT aggregate (which eliminates the need for purification treatment for removing impurities) as it is formed on the substrate.
[0100]
[Embodiment 5]
(Tensioning of CNT)
FIG. 30 is a schematic diagram illustrating a state of stretching CNTs manufactured by arc discharge according to Embodiment 5 of the present invention. In FIG. 30, when a CNT tape having a width of 3 mm and a length of 10 mm (see (a) of FIG. 30) is pulled in the longitudinal direction, the CNT tape is broken in the middle, and the CNT fiber tip is exposed on the broken surface as if it were fluffy. (Hereinafter, one after fracture is referred to as a work piece, see FIG. 30 (b)).
Therefore, by attaching the processed piece to the substrate E1 (see (c) of FIG. 30), or by arranging a plurality of processed pieces and attaching them to the substrate E1 (see (d) of FIG. 30), a good electron emission source can be obtained. Can be obtained.
[0101]
(Situation of tensile break of CNT)
FIG. 31 is an electron micrograph showing a side surface after CNTs produced by arc discharge according to Embodiment 5 of the present invention have been subjected to tensile processing. FIG. 31 is an electron micrograph showing the vicinity of the fractured surface from the side, and the CNT fiber extends into the open space at an angle nearly perpendicular to the fractured surface. Further observation of this part revealed that most of the CNT fibers had ends (the same is true of the case where there were few loop-shaped fibers in which both ends penetrated into the CNT aggregate and appeared halfway along the fracture surface).
The term “end” as used herein means both the end at which the CNT fiber is broken and the surface closed with carbon atoms specific to the CNT fiber (the end of the CNT fiber having the end in the originally formed state). .
The electron emission characteristic in such a small range focusing only on the tensile fracture surface is 50 μA / mm. ^Two In order to obtain an average current density of 5 kV / mm, an average electric field strength of 5 to 6 kV / mm is sufficient, and an extremely good value is shown.
[0102]
(Peeling of CNT)
FIG. 32 is a schematic diagram illustrating a state of peeling off CNTs manufactured by arc discharge according to Embodiment 5 of the present invention. In FIG. 32A, the back surface (cathode side) of the CNT tape C21 is attached to the electron emission source substrate E1, and the front surface (anode side) B2 is attached to another electron emission source substrate E2 (adhesives B1, B2, respectively). by).
Then, in (b) of FIG. 32, when the electron emission source substrates E1 and E2 were peeled off, the CNT tape C21 was peeled off in the middle in the thickness direction. That is, the inside of the CNT aggregate newly appears on the surface with the CNT tape C21 adhered to each of the electron emission source substrates E1 and E2.
[0103]
(Peeling surface)
FIG. 33 is an electron micrograph showing a processed surface of a CNT produced by arc discharge according to Embodiment 5 of the present invention. In FIG. 33, on the surface after peeling (before peeling, the inside of the CNT aggregate), the amount of impurities found on the surface of the CNT tape as manufactured was drastically reduced. Are much exposed.
[0104]
(Electron emission characteristics of peeled surface)
When the electron emission characteristic of the electron emission source using the peeled CNT aggregate was examined, it was found to be 50 μA / mm. ^Two In order to obtain an average current density of 5 to 6 kV / mm, an average electric field strength of 5 to 6 kV / mm may be sufficient, and the electron emission characteristics are improved as compared with the case where the CNT aggregate before peeling (unrefined state) is used. I understand.
The reasons for this are not clear, but (a) the impurities are extremely small, (b) the ends of many CNT fibers are fluffy exposed on the surface, and (c) some CNT fibers are CNT aggregated. This is probably because the graphene sheet of the CNT fiber, which is broken near the surface of the body and is generally closed, is shredded and the end of the graphene sheet is exposed.
[0105]
(Electron emission characteristics of processed piece of CNT aggregate)
The electron emission characteristic of the CNT aggregate according to the present invention is 50 μA / mm. ^Two In order to obtain an average electron emission density of about 6 to 8 kV / mm, it is only necessary to apply a voltage for obtaining an average electric field strength of about 6 to 8 kV / mm. It is only necessary to apply a voltage for obtaining the strength.
On the other hand, even when CNTs generated by a general arc discharge method are purified and coated with a substance having an infinitely high purity, it is necessary to apply a voltage to obtain an average electric field strength of 7 kV / mm. Therefore, it can be said that the electron emission characteristics of the CNT aggregate according to the present invention are extremely excellent.
Therefore, when the CNT aggregate according to the present invention is used as an electron emission source, it is only necessary to adhere the CNT aggregate in a non-refined state (the purification process for removing impurities is not required) on the substrate.
[0106]
Embodiment 6
Hereinafter, use of CNTs manufactured by arc discharge according to the sixth embodiment of the present invention will be described.
(area)
When considering the actual use of CNTs, CNTs having an area as needed are required. In the prior art, an integrated CNT aggregate having a large area can be obtained by a chemical process such as a vapor phase growth method, or by applying or spraying CNTs as a powder, regardless of the generation method. I had no choice but to configure the surface.
[0107]
However, in a chemical process typified by a vapor phase growth method (CVD method), for example, when CNTs are grown on a flat substrate, it is difficult to locally change the growth rate, and almost no irregularities occur. In addition, the CNTs formed by the vapor phase epitaxy method have disordered and meandering owing to their low crystallinity, so that a CNT aggregate having almost no unevenness (very smooth) on the surface is obtained. (Note that, as described later, the surface of the CNT fiber produced by the CVD method is not smooth, and the CNT fiber according to the present invention has a smooth and straight surface.)
[0108]
When powdered CNTs produced by an arc discharge method or a vapor phase growth method are applied or sprayed on a flat plate, they are also likely to be uniformly sprayed, and at least a dense set and a sparse set are narrowly spaced, for example, every 20 μm. Can not be mixed.
On the other hand, the aggregated CNT according to the present invention is not only a 0.1 mm square (for example, a region considered to be a necessary minimum as an electron emission source), but also a 4 mm diameter circle or a 5 mm width and a length of 5 mm. Various dimensions such as a rectangular shape of 10 mm and a long tape shape can be generated.
That is, as a result of various examinations of the generation conditions, a material having a high resistivity was selected as the cathode material, the cathode discharge generating section was preheated, and the CNT generation rate of the cathode discharge generating section was increased.
[0109]
(purity)
It is desirable that the CNT aggregate has a higher purity regardless of the intended use. Here, if the purity as seen from at least one side is 99% or more, impurities (explained separately below) are substantially ignored particularly as the electron emission source, the adsorbent, the filter material, and the heat radiation material. be able to.
Further, the amount of the impurities attached only to the surface of the CNT aggregate (the surface on the anode side) is a very small amount with respect to the CNT aggregate, and can be neglected when the impurities are extremely small. That is, since the CNT aggregate according to the present invention has a purity of 99% or more in a non-refined state (the same as deposited immediately after arc discharge), it can be used as an industrial material without purification treatment. is there.
Here, the purity means the ratio of the total CNT area obtained by adding the area occupied by the CNT aggregate to the total area of the cathode volume in a specific visual field, and substantially equals a predetermined volume of the cathode deposit. It is the same as the ratio of the total volume of the CNT fibers occupying.
[0110]
(impurities)
Further, when the size of the impurities is extremely small compared to the diameter of the CNT fibers or the gap between the CNT fibers, it does not affect the electric field when used as an electron emission source. When used, the fluid is less contaminated by the removal of impurities, and has little effect on adsorbents, heat dissipating materials, or other materials requiring a surface area.
From this, if the size of the impurities is about 100 nm or less in diameter (belonging to a thick category as CNT fibers), there is substantially no harm, and it can be industrially treated with a purity equivalent to 100%. There are cases.
[0111]
Further, when the CNT aggregate is used as the adsorbent and the heat dissipating material, the higher the actual surface area of the CNT fibers constituting the CNT aggregate, the better the performance. For this reason, the purity of the entire CNT aggregate is more important than the purity observed from one side. As long as the purity (the ratio of the CNT fibers) of the entire CNT aggregate is 80% or more, the CNT aggregate can be used for the above purpose.
It should be noted that the purity referred to here is a value observed in the entire CNT aggregate (the whole including both a dense region and a sparse region described later) and a local region (a dense region or a sparse region described later). May be 80% or less.
[0112]
(Use of electron emission characteristics)
{Circle around (1)} It can be used as an electron emission source, and it is possible to easily manufacture electric / electronic devices using the same, for example, a photoelectric tube or a flat panel display.
(2) Due to the excellent fineness and crystallinity of the CNT fiber, it is used as a field emission electron source for cathode materials such as fluorescent display tubes and field emission displays (FED), and as a probe for electron microscopes. Can be considered.
{Circle around (3)} By using the CNT aggregate as the electron source, it is considered that an efficient ion or ozone generator can be manufactured. It has been reported that these ions and ozone have a deodorizing and deodorizing effect, and particularly that negative ions have a positive effect on human psychological and physiological aspects.
[0113]
(Use of electron emission characteristics-size of electron emission source)
By the way, when CNT is used as an electron emission source, electron emission characteristics capable of realizing a higher current at a lower voltage are desired. In terms of voltage, it is effective to increase the electric field strength by the shape effect of the CNT. For that purpose, it is said that it is effective to increase the aspect ratio of the CNT, particularly to reduce the diameter.
However, when the density of the CNTs is increased, the surface becomes more smoother macroscopically, and the electric field strength at the tip of the CNTs decreases. For this reason, it is said that in an electron emission source on which CNTs are applied at a high density, it is better to increase the electric field strength at the CNT tip by making the orientation irregular, so that the electron emission characteristics are more excellent.
[0114]
In terms of current, there are a method of increasing the number of layers of the CNT fibers to be configured to increase the current capacity per fiber, and a method of increasing the density of the CNT aggregate while maintaining the current capacity per fiber. .
In the former case, there is a correlation between the current capacity and the cross-sectional area of the CNT, and the upper limit naturally has an upper limit because the aspect ratio of the CNT fiber affects the electron emission characteristics. In the latter case, according to the conventional coating method or the like, CNTs are further laminated on the CNTs directly in contact with the substrate, and the contact of each CNT is a small number of point contacts. The current capacity of this point contact portion is significantly lower than that of the CNT and burns out immediately, so that the CNT deposited on the upper portion does not not only function as an electron emission source but also deteriorates the electron emission characteristics as an impurity.
[0115]
To cope with this problem, the CNT aggregate according to the present invention is a CNT aggregate having excellent electron emission characteristics because a plurality of CNT fibers are intricately entangled in a flocculent manner. Furthermore, the orientation of each CNT fiber on the surface of the CNT aggregate is irregular, and the electric field strength at the tip of the CNT fiber can be further increased.
In addition, regarding the contact between the CNT fibers, since the CNT fibers have a large number of contact points and can obtain stronger contact due to the elasticity of the CNT fibers, even when the surface is a high-density CNT aggregate, it is sufficient. It is possible to have a current capacity, and to obtain an electron emission source that can obtain a higher current.
Since the CNT fibers on the surface of the CNT aggregate according to the present invention are irregularly oriented, the electron emission characteristics tend to vary when the area is small, and in order to obtain uniform electron emission characteristics as an electron emission source, It is necessary that at least one side has a length of 1 mm or more. The length of the side in this case includes the diameter of the circle and the radius of the ellipse.
[0116]
(Utilization of electron emission characteristics-CNT fiber size)
As described above, when CNT is used as an electron emission source, it is desirable to obtain a CNT fiber shape having excellent electron emission characteristics. The electric field strength at the tip of the CNT is determined by the aspect ratio if the CNT is a simple substance. However, if the CNT fiber has a length of 1 μm or more, it is hardly affected by the length and almost depends on the diameter of each CNT fiber. The electric field strength is determined.
This is because most of the single CNT fibers are buried in the CNT aggregate, so that the protrusion length of the CNT fibers that protrude from the macroscopic surface of the CNT aggregate and the length and diameter of the protruding length portion This is because the electric field intensity is determined by the aspect ratio.
[0117]
As a result of a test conducted by the inventors, it was possible to obtain a sufficient electric field intensity as an electron emission source with a CNT aggregate composed of CNT fibers having a diameter of 15 nm or less. As for the current capacity, a sufficient current capacity as an electron emission source could be obtained with an aggregate composed of CNT fibers having a diameter of 4 nm or more.
Therefore, a CNT aggregate composed of 4 to 15 nm CNT fibers is suitable as an electron emission source. In addition, regarding the purity (constituent ratio), if 50% or more of CNT fibers having a diameter of 4 to 15 nm are contained, even if CNT fibers of other diameters and impurities of 50% or less are mixed, the electron emission characteristics are not improved. It is possible to use it as an electron emission source without much influence.
[0118]
(Utilization of electron emission characteristics-Volume density of CNT aggregate)
When the constituent CNT fibers are densely gathered, the surface of the CNT aggregate becomes smoother when viewed macroscopically. In an extreme case, considering an aggregate having a density of 100%, the surface becomes a plate-like substance having a smooth surface, and the electric field intensity applied to each CNT decreases.
For this reason, it is desirable that the CNT aggregate used as an electron emission source is sparsely aggregated to some extent, and more desirably has a cotton-like opening when viewed from the surface.
[0119]
From this, the volume density excellent in the electron emission characteristics is naturally determined. However, as a result of investigation by the inventors, the volume density, that is, the ratio of the actual volume occupied by the CNT fibers to the apparent volume of the CNT aggregate is 1/10 or less. In this case, it can be used as an electron emission source, and when it is 1/50 or less, good electron emission characteristics can be obtained. In the actual CNT fiber aggregate, since the CNT fibers were intricately entangled and it was difficult to measure the volume density, the actual CNT aggregate was calculated by multiplying the volume density by the density of graphite. The volume density is determined from the mass ratio.
[0120]
(Utilization of electron emission characteristics-CNT fiber contact interval)
In a CNT aggregate in which the length of each CNT fiber is short, the number of contact points between the CNT fibers decreases, resulting in a decrease in electric conductivity and current capacity. That is, as the number of contact points increases, the electrical contact between the CNT fibers is ensured. On the other hand, when considering the electron emission characteristics, the potential of each CNT fiber is close to the contact point where the CNT fibers contact. Since they are almost equal (the potential difference is extremely small), the electric field intensity is reduced, and a high electric field intensity is required for electron emission.
[0121]
Therefore, the distance (ab-ac) between one contact point ab at which one CNT fiber b contacts one CNT fiber a and another contact point ac at which the other CNT fiber c contacts one CNT fiber a is determined. When the contact interval is set, if the contact interval is too small, the electron emission characteristics deteriorate.
For this reason, it is necessary that the contact interval is longer than a certain level. Actually, the relationship between the contact interval and the electric field intensity varies depending on the crossing angle, the diameter of each CNT fiber, and the surrounding shape, but it is preferable that the contact interval includes those separated by 5 μm or more. In particular, in a visual field having a surface of 10 μm square, good electron emission characteristics can be obtained by including a plurality of lines.
[0122]
(Utilization of electron emission characteristics-Crystallinity of CNT fiber)
The crystallinity of the CNT fibers constituting the CNT aggregate greatly affects the electron emission characteristics of the aggregate as a whole. When the crystallinity is poor, not only the electrical conductivity of the CNT fiber itself is reduced and the current capacity is reduced, but also the entire length or a part of the CNT fiber is insulated from other CNT fibers and hinders electron emission.
However, strict evaluation of the crystallinity requires use of a technique such as Raman scattering, and it is difficult to evaluate the crystallinity of the CNT fiber over a wide area of the CNT aggregate.
[0123]
FIG. 34 is a schematic diagram comparing the characteristics of CNT fibers with respect to the use of CNTs produced by arc discharge according to Embodiment 6 of the present invention. The CNT fiber produced by the present invention shown in FIG. 34A is substantially straight, has a substantially uniform diameter, and does not branch in the middle. On the other hand, in the CNT fiber generated by the vapor phase growth method (CVD method) shown in FIG. 34B, the CNT fiber that should originally grow linearly grows in a meandering manner, or has a branch in the middle. The outer diameter changes midway in the longitudinal direction.
In general, the vapor phase growth method (CVD method) is considered to have lower crystallinity than the arc discharge method, and the grounds include the above-mentioned bending, branching, and uneven diameter of the CNT fiber. Those without branching can be evaluated as having good crystallinity. Therefore, it is considered that the CNT aggregate constituted by the non-branched CNT fibers according to the present invention has better performance as an electron emission source.
[0124]
(Utilization of electron emission characteristics-entanglement of CNT fibers)
When the CNT aggregate is used as an electron emission source, it is important to ensure electrical contact between the CNT fibers and to increase crystallinity. Here, CNTs having good crystallinity, which originally grow linearly, are intricately entangled with each other, thereby causing elastic deformation of the CNT fibers, ensuring contact, and improving electrical contact between the CNT fibers, so-called electrical conductivity. It has the effect of improving.
[0125]
(Use of electron emission characteristics-dense and dense area of CNT aggregate)
Furthermore, when a CNT aggregate is used as an electron emission source, it is needless to say that, when viewed from a macroscopic perspective, a uniform density results in a smaller variation in performance between the CNT aggregates. If the density is high, the electric field strength can be increased, and the electron emission characteristics are improved. That is, since the CNT aggregate according to the present invention includes the first region in which the CNT fibers are densely gathered and the second region in which the CNT fibers are loosely gathered, the CNT aggregate exhibits good electron emission characteristics. It is considered.
[0126]
Note that the first region (where the CNT fibers are densely packed) desirably has more contact points between the CNT fibers as an electron emission source, and has a larger surface area as an adsorption material or a heat dissipation material. It is desirable to increase the volume density 1 (bulk specific gravity 1.8 g / cm ^Three , The same is true). However, in order to form a flocculent CNT aggregate, it is necessary to allow a certain amount of voids. Further, in order to recognize the region as being distinct from the second region, that is, to define that the CNT aggregate has a sparse and dense region, the volume density is 1/5 or more (the bulk specific gravity is 0.36 g / cm3). ^Three ) Is defined as a dense area.
[0127]
On the other hand, in the second region (CNT fibers are sparsely aggregated), ideally, from the viewpoint of electric field strength, it is desirable that no CNT fibers are contained. 100 (0.0225 g / cm ^Three ) The following may be sufficient. In other words, when the volume density is 1/100 or less, the distance between adjacent CNT fibers is 10 times or more the diameter of the CNT fibers when observed two-dimensionally on average, so that it is irregular in the actual three-dimensional space. In the arranged state, the CNT fiber has a diameter of 30 times or more of the diameter of the CNT fiber, and can be considered to be equivalent to a region not including any fiber.
Further, the reference volume for determining the density varies depending on the size of the visual field. For this reason, in order to evaluate the electron emission characteristics in order to increase or decrease the strength of the electric field, it is desirable to view a region obtained by cutting out a rectangular parallelepiped having a side of 2 μm.
[0128]
(Utilization of electron emission characteristics-unevenness of dense / dense area of CNT aggregate)
Furthermore, the CNT aggregate according to the present invention has a region where CNT fibers are densely aggregated and a region where CNT fibers are sparsely aggregated on its surface. The densely gathered area is convex as a conical shape with a sharp tip. Since this convex region includes many ends of the CNT and is more convex than the other portions, the electron emitting ability is high in combination with the high electric field intensity due to the shape effect. Furthermore, since the convex region is distributed almost uniformly, the distribution of the electron emission current density when viewed as the surface of the CNT aggregate should be substantially uniform when viewed macroscopically. Can be.
[0129]
Furthermore, the convex portion (the densely gathered region) of the CNT aggregate according to the present invention has a large number of CNT fibers on the base side (corresponding to the side opposite to the open space and the cathode side) due to a large number of CNT fibers. Therefore, more current can flow. In addition, the number of CNT fibers constituting the tip gradually decreases toward the tip (corresponding to the anode side or the fracture surface side), and the tip of the convex region is one or a few CNTs. .
For this reason, the electron-emitting device exhibits a remarkable electron emission source characteristic that the electric field intensity is increased by the effect of the sharp point and the shape effect of the projection. Further, as will be described later, even more excellent electron emission characteristics can be obtained by positively pulling out the sharp portion toward the open space side with respect to the surface of the CNT aggregate.
[0130]
(Utilization of electron emission characteristics-interval between dense and dense areas of CNT aggregate)
When CNT is used as an electron emission source, it is necessary to ensure excellent electron emission characteristics and uniformity of electron emission current density on the electron emission surface. For that purpose, it is desired that the part where the electric field strength is raised toward the open space and the part where the electric field strength is concave and the electric field strength is low are distributed to some extent densely and uniformly.
[0131]
The appropriate value of the interval naturally depends on the target product and the size, particularly the area, of the electron emission source. However, for example, even if a flat panel display having a resolution of 300 dpi is considered, each light-emitting portion is a square of 80 μm on a side, and if the interval between the convex regions is 40 μm or less, a plurality of light-emitting portions must be formed at this resolution. Is included in each light emitting unit.
Considering that even a liquid crystal of a computer having a relatively high resolution is about 150 dpi, if the interval between the convex regions is 40 μm or less, more preferably 20 μm or less, the uniformity of the electron emission source is as follows. It is considered that there is no practical problem.
[0132]
Also, considering the case where the interval between the convex regions is extremely small, the electron emission surface of the CNT aggregate is further smoothed, and it is difficult to obtain a high electric field intensity due to the shape effect. For this reason, it is desirable to have at least an interval of 100 times or more the diameter of the CNT fiber. Considering that the diameter of the CNT fiber having excellent electron emission characteristics is 20 nm or less, the interval between the convex regions is 2 μm. It is more preferable that the particles are distributed with an interval of 5 μm or more.
[0133]
From this, industrially, in the electron emission surface, in the field of view of 40 μm on a side, at least an adjacent interval is 2 to 40 μm, more preferably a region where CNTs are gathered in a convex shape at an interval of 5 to 20 μm. Desirably it is present.
Note that the upper limit of the adjacent interval is a distance equivalent to the radius of the electron emission region when used as an electron emission source (for example, the length of one side of a rectangular electron emission region (for example, a square electron emission source having a side length of 200 μm). Is 100 μm), that is, half of the square root of the area of the electron emission region), the predetermined performance is exhibited without any problem as to the uniformity. Even more preferably, even with a half of the radius of the electron emission source region (1/4 of the square root of the area of the electron emission region, 50 μm in the above example), there is no problem in terms of uniformity, and particularly high electron emission current can be obtained. If not required, this value can be used. Needless to say, the field of view in this case is the area of one region of the electron emission source.
[0134]
(Utilization of electron emission characteristics-CNT fibers constituting dense area of CNT aggregate)
Further, in order to form a dense / dense region in the CNT aggregate, the length of the CNT fiber including the region needs to be 10 μm or more.
That is, in order to form a CNT aggregate having a sparsely aggregated region and a densely aggregated region, it is necessary to include at least a CNT fiber having a length straddling the densely aggregated region. When the interval between the regions that are gathered is 5 to 20 μm, the sparsely gathered region (located in the middle of the densely gathered region) has an average spread of 10 μm. CNT fibers of 10 μm or more are required.
[0135]
In addition, since the CNT fibers are very small and the distance between the CNT fibers is very small, an intermolecular force acts between the CNT fibers, and the CNT fibers are attracted to each other. Although the intermolecular force is extremely small, if the CNT fiber is sufficiently long, it is considered that the CNT fiber grows gradually and gradually attracts each other to finally generate a densely aggregated region and a sparsely aggregated region. Can be
On the other hand, when the length of the CNT fibers is less than 10 μm, it is considered that the bonding between the CNT fibers in the portion where the CNT fibers are sparsely assembled is weak (the number of contact points themselves is reduced) and the CNT fibers cannot be formed as an aggregate.
[0136]
(Utilization of electron emission characteristics-tip of CNT fiber)
When a plurality of CNT fibers are entangled and the aggregate integrated into a cotton is divided (see FIG. 32), the CNT fibers having ends are extended from the division surface to the open space. This is because the CNT fibers originally grow linearly, and the binding force applied to the CNT fibers having some ends near the division surface changes or releases, and the CNT fibers are bent in an arc shape due to constraints from other members. It is considered that the fibers returned to a straight line.
In addition, it is considered that a part was forcibly reoriented from the dividing surface toward the open space due to the deformation force at the time of dividing. Either way, the CNT tip having an end extending from the division surface into the open space has a high electric field intensity due to the shape effect, and when used as an electron emission source, high electron emission characteristics can be obtained.
[0137]
FIG. 35 is a schematic diagram showing the characteristics of CNT fibers regarding the use of CNTs produced by arc discharge according to Embodiment 6 of the present invention. FIG. 35 (a) shows a CNT fiber whose tip is torn by pulling (see FIG. 30), and FIG. 35 (b) shows a solid CNT fiber whose tip is also torn. In either case, the end (fracture surface) of the graphene sheet forming the tube is exposed to the space.
From this, the reason for the high electron emission characteristics is considered as follows.
[0138]
(Reason 1) In the CNT aggregate according to the present invention, impurities were found only on the surface of the CNT aggregate, although the amount was small (adhesion process or subsequent deposition). When used as an electron emission source, these impurities not only do not contribute to electron emission, but also act as a mask and hinder electron emission from the surface. For this reason, it is desirable to remove impurities as much as possible and expose the clean portion inside the assembly to the surface.
[0139]
(Reason 2) In order to enhance the electron emission characteristics, since the electric field intensity increases due to the shape effect, it is desirable to expose a large amount of the CNT fiber tips to the surface.
That is, by cutting the CNT aggregate according to the present invention, many ends of the CNT fiber are exposed. This can easily be imagined from the fact that when the cotton is shredded, many of the fiber ends are exposed on the fracture surface.
[0140]
(Reason 3) In the present invention, by applying a tensile force to the CNT aggregate, the CNT fibers intricately entangled in a flocculent form are unraveled or broken. The broken ends appear with the ends of the unraveled CNT fibers and the CNT fibers broken at a certain probability oriented in the tensile direction. Naturally, the edge of the graphene sheet of each layer forming the CNT fiber is exposed in this fractured surface, and has high electron emission characteristics.
[0141]
In addition, CNTs (for example, carbon nanohorns) generated by the CVD method or the like, in which both ends of the carbon fiber on the tube are completely closed in a conical shape, are compared with those of the both ends of the tube by oxidation treatment or the like. It has been reported that electron emission characteristics can be improved by breaking a carbon bond to expose the end of a graphene sheet constituting a tube at the tip of the tube.
[0142]
(Low volume density, use of surface area)
{Circle around (1)} The volume density of the CNT aggregate is 1/10 or less of that of graphite, and since the CNT fibers are intricately entangled, it can be used as a filtering material.
{Circle around (2)} Further, since the effective surface area is large, it can be used as an adsorbent similarly to activated carbon, and the amount of adsorption per weight is expected to be larger than that of activated carbon.
{Circle around (3)} The CNTs produced by the conventional method are small in size, have a diameter of 70 nm or less, and a length of less than 10 μm are weak mechanical joints. In other words, they are merely deposited and adhered. Is separated by flowing, and flows together with the powder, whereas the aggregate of the present invention is not easily collapsed in a fluid, so the aggregate itself can be used as the functional film or the functional body as it is. is there.
(4) Cotton-like CNT tape in which CNTs with nano-sized diameters are intricately intertwined has a certain size of space determined by the density of the CNT tape. It can be used as a filter or a separation membrane.
{Circle around (5)} Moreover, the surface area per unit weight exceeds that of activated carbon, and it can be used as an adsorbent for harmful substances or a gas storage material for hydrogen or methane.
[0143]
FIG. 36 is a schematic diagram illustrating a filter using CNTs manufactured by arc discharge according to Embodiment 6 of the present invention. In FIG. 36, F1 has a cylindrical filtering part F3 between a fluid inlet F2 and a fluid outlet F5, and a filter is disposed in the filtering part F3. The filter body is formed by an aggregate layer in which a plurality of CNT aggregates C21 are arranged in a plane, and the front and back surfaces of the aggregate layer are kept in a single layer or in a state in which a plurality of CNT aggregates C21 are stacked. Is held by This prevents the CNT aggregate from being agitated and broken into pieces when the fluid passes.
By using these, application to a filter, a filter for adsorbing a specific substance, a filter for adsorbing a specific substance, or a deodorizing apparatus that can transmit only a specific substance in a liquid or a gas can be expected. The CNT aggregate may be the CNT tape or the work piece.
[0144]
(Use of heat dissipation characteristics)
{Circle around (1)} When the CNT aggregate according to the present invention was mounted on an aluminum plate and the heat radiation characteristics were measured, the heat radiation effect was improved by 20% as compared with the case without the aggregate. This is attributed to the heat dissipation characteristics of the aggregate itself, for example, the size of the effective surface area due to being cotton-like, and the good thermal conductivity due to long CNTs having many good heat transfer contact points. Conceivable.
That is, the heat radiation performance can be expected to be improved not only by the metal plate but also by, for example, sticking to a semiconductor integrated circuit. In addition, as an example of utilization, it is possible to improve the adhesiveness and efficiently transmit heat by sandwiching the heat transfer material between the cooling fin and the object to be cooled by utilizing the height of heat conduction.
[0145]
(Use of tensile strength)
(1) The fact that the crystallinity is excellent means that the strength of the CNT is high. That is, the CNT fiber has a tensile strength of 100 times or more theoretically that of iron, and the specific gravity is about half of that of aluminum. Therefore, the CNT fiber may be mixed with resin or metal, or may be mixed with resin or metal and CNT. A light, high-strength structural material can be manufactured.
{Circle around (2)} As its name suggests, it has a nano-sized size, so it can be used as a structural member of a micromachine or a component of an actuator.
[0146]
In order to integrate a plurality of CNT fibers, the CNT fibers need to be combined with some force. For example, when the CNT fibers are all linear, the bond between the CNT fibers is basically only an intermolecular force or a frictional force.
Of course, when considering a plurality of CNT fibers, it is possible to secure the bonding force by sandwiching them intricately. However, considering the case where an external force, for example, a tensile force is applied, each CNT fiber is in the direction of the external force or It is easily imagined that they are oriented in the deformation direction. The bonding between the CNT fibers oriented in almost one direction in this way is only an intermolecular force or a frictional force.
[0147]
On the other hand, the CNT fiber having a curved shape is entangled with other CNT fibers, and furthermore, the CNTs are connected to each other. In addition to the intermolecular force and the frictional force, the shearing force with the other CNT fibers is increased. And various forces such as pulling force. For this reason, the strength of the CNT fiber itself is higher than that of steel, and the CNT aggregate is more strongly integrated to have a predetermined strength. That is, the CNT aggregate can remain as it is without being decomposed even by a relatively small force, for example, a force for lifting the CNT aggregate, an external force acting when immersed in a liquid, and the like.
Therefore, if the CNT aggregate includes 30% or more of CNT fibers curved with a predetermined curvature, desired strength can be secured.
[0148]
Needless to say, in order to handle as a CNT aggregate, it is desirable that each CNT fiber has high strength.
CNTs are broadly divided into single-walled CNTs having only one graphene sheet, two-layered CNTs having three layers, and multi-layered CNTs having three or more layers. It is desirable that the CNT fiber constituting the body is constituted only by the multilayer CNT.
However, the mechanism of CNT generation has not been completely elucidated, and the number of CNT fibers constituting the CNTs is in the range of tens of thousands to hundreds of millions or more. could not say it all.
Therefore, if it is substantially composed of multilayer CNTs, it can be handled as an aggregate in terms of strength. For example, it is preferable to include multilayer CNTs in a composition ratio of 95% or more.
[0149]
Many CNT fibers according to the present invention include those having a curvature radius of 1 μm or more and a curvature radius of 10 μm or less, whereas CNT fibers produced by a vapor phase growth method (CVD method) are bent (curvature) due to poor crystallinity. (The radius is on the order of 100 nm) and the strength of the CNT fiber is generally low, so that the CNT fiber is easily cut.
[0150]
In addition, as described above, the CNT fibers according to the present invention have good crystallinity and high strength, and each CNT fiber is elastically deformed and has high deformability, so that the CNT fiber hardly breaks even when deformed. Furthermore, since each CNT fiber is long, it has a feature that it is hard to be broken even as an aggregate.
For this reason, in the CNT aggregate obtained as a cotton-like structure entangled at the time of CNT generation, the CNT fibers are complicatedly entangled and mechanically firmly bonded, thereby suppressing separation and falling off from the CNT aggregate. .
This improves the handling of the CNT aggregate as various materials, and enables the CNT aggregate to be attached to a spherical or curved substrate.
[0151]
On the other hand, the CNT fibers manufactured by another process such as the CVD method are not entangled with each other. In addition, when powdered CNTs are manufactured by a process such as stirring, the CNTs which are originally independent are simply mechanically entangled in the subsequent process, so that they are easily unraveled. It is conceivable that the removed CNTs become slag, fall off, lose electrical conduction, and become impurities. Furthermore, this tendency becomes remarkable when exposed to flowing gas or liquid.
[0152]
(Use of conductivity)
{Circle around (1)} Because of its excellent conductivity, it can be used as a wiring material for ICs.
{Circle around (2)} By mixing with resin or fiber, these substances can be made conductive or have a function of preventing static electricity.
{Circle around (3)} The use of a conductive coating film or conductive ink mixed in a paint is also conceivable.
These materials can be used as members that require conductivity, and can also be used as electromagnetic wave absorbing / shielding materials based on electromagnetic wave reflection loss and dielectric loss.
{Circle around (4)} Further, by mixing with the negative electrode material of the secondary battery, it is possible to prevent the negative electrode conductivity from aging.
{Circle around (5)} Further, it is considered that by mixing the grease, the grease can be made conductive, and the performance of the grease can be prevented from deteriorating in the current-carrying portion.
{Circle around (6)} Use as an electrode material for a capacitor is also conceivable.
[0153]
(Use of conductivity-contact between CNT fibers)
In a CNT aggregate in which the length of each CNT fiber is short, the number of contact points between the CNT fibers decreases, resulting in a decrease in electric conductivity and current capacity. Furthermore, by increasing the length of each CNT fiber and intricately tangling the CNT fibers, the contact force between the CNT fibers can be increased, and the electrical conductivity and the current capacity can be improved. For this purpose, it is necessary to include CNT fibers having a length of 10 μm or more, mostly at a ratio of 50% or more, more preferably at least 80% of the composition ratio of the CNTs.
FIG. 37 is a schematic diagram showing the characteristics of CNT fibers regarding the use of CNTs produced by arc discharge according to Embodiment 6 of the present invention.
For example, considering the case where CNT fibers are connected in series, the length of the CNT fibers made by the conventional technique is 1 μm (FIG. 37A), and the length of the CNT fibers included in the aggregate of the present invention is 10 μm ( As shown in FIG. 37 (b)), the contact points between the CNT fibers when the circuit length is the same are reduced to 1/10.
Since the resistivity at the contact point is higher than the resistivity of the CNT fiber alone, the conductivity as an aggregate can be increased by decreasing the contact point, that is, by increasing the length of the CNT fiber.
[0154]
Considering the case where the CNT fibers are connected in a grid at the same density, the contact points of the grid formed by the CNT fibers F1 and G1 having a length of 1 μm (FIG. 37 (c)) At the lattice points ((d) in FIG. 37) of the lattice formed by the CNT fiber F10 and the CNT fiber G10 having a length of 10 μm, the length of the latter CNT fiber is longer, in other words, more. Therefore, the conductivity of the aggregate can be increased as an effect of the parallel connection.
Therefore, as the length of the CNT fiber is longer, for example, 20 μm or more than 50 μm has the effect of improving the conductivity of the aggregate, but since the CNT fiber constitutes a complicatedly entangled flocculent aggregate, for example, 10 μm It is sufficient that the CNT fibers having a length of at least 50% or more, or the CNT fibers having a length of 30 μm or more are 40% or more, or the CNT fibers having a length of 50 μm or more are included in any one of 30% or more.
[0155]
(Use of thermal conductivity)
{Circle around (1)} Since CNT has thermal conductivity higher than that of diamond, it can be used as a heat dissipating material for ICs and the like. When used as a heat radiating material, a single material or a material mixed with a resin or metal may be used. Also, it is considered that the heat radiation characteristics can be greatly improved by applying or sticking to a surface of an aluminum plate or the like.
[0156]
(Use of quantum effect)
{Circle around (1)} Further, CNTs, which are extremely small structures of nano size, can be used as materials for electronic components such as diodes and transistors using quantum effects and quantum dots which are basic elements of quantum computers. .
[0157]
(Use of functionality)
{Circle around (1)} Further, use as a functional material such as a gas sensor for detecting a specific gas can be considered.
{Circle around (2)} It is thought that the efficiency of various chemical reactions can be improved by using the catalyst as a carrier material.
(3) Furthermore, in the medical field, etc., there is a possibility that it can be used as a carrier for adsorbing and holding a drug or the like and transporting it to a lesion in the body.
[0158]
【The invention's effect】
As described above, the CNT fibers according to the present invention are sufficiently entangled with each other, so that a CNT aggregate having a high CNT purity and a CNT installation device provided with the CNT aggregate can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing Example 1 (CNT manufacturing apparatus 1) of a CNT manufacturing apparatus in a method of manufacturing CNT generated by arc discharge according to Embodiment 1 of the present invention.
FIG. 2 is a schematic view showing a CNT manufacturing apparatus 2 (cooling anode) of the present invention.
FIG. 3 is a schematic view showing a CNT manufacturing apparatus 3 (preheated cathode) of the present invention.
FIG. 4 is a schematic diagram showing a CNT manufacturing apparatus 4 (gas supply anode) of the present invention.
FIG. 5 is a schematic view showing a CNT manufacturing apparatus 5 (anode with nozzle) of the present invention.
FIG. 6 is a schematic view showing a CNT manufacturing apparatus 6 (moving anode) of the present invention.
FIG. 7 is a schematic view showing a CNT manufacturing apparatus 7 (rotating cathode) of the present invention.
FIG. 8 is a thermoviewer photograph showing a result of temperature measurement of an arc discharge part in the CNT manufacturing apparatus 2 (cooling anode).
FIG. 9 is a thermoviewer photograph showing a result of temperature measurement of an arc discharge part in the CNT manufacturing apparatus 2 (cooling anode).
FIG. 10 is a schematic diagram showing Example 1 (CNT manufacturing method 1) of the method for manufacturing CNT according to Embodiment 3 of the present invention.
11 is a scanning electron microscope (SEM) photograph showing a result of observing a cathode spot when an arc is generated for a short time by the general discharge of FIG. 10;
FIG. 12 is a schematic diagram showing CNT production method 3 (preheated cathode) of the present invention.
FIG. 13 is a schematic diagram showing an arc discharge state in CNT manufacturing method 4 (gas supply anode) of the present invention.
FIG. 14 is a scanning electron microscope (SEM) photograph showing CNTs generated in CNT production method 4 (gas supply anode) of the present invention.
FIG. 15 is a graph of an experimental result showing a relationship between a discharge gas flow rate and an arc generation mode in CNT manufacturing method 4 of the present invention.
FIG. 16 is a schematic diagram illustrating a situation in which catalyst powder is mixed into a discharge gas in CNT manufacturing method 4 of the present invention.
FIG. 17 is a schematic view showing CNT manufacturing method 6 (moving gas supply anode) of the present invention.
FIG. 18 is a schematic diagram in which a mechanism for producing a high-purity CNT tape in a CNT production method 6 (moving gas supply anode) of the present invention is estimated.
FIG. 19 is an electron micrograph showing a high-purity CNT tape produced by CNT production method 6-2 of the present invention.
FIG. 20 is a schematic view showing CNT production method 7 (gas supply anode) of the present invention.
FIG. 21 is a photograph showing the appearance of a high-purity CNT tape produced in CNT production method 7 (gas supply anode) of the present invention.
FIG. 22 is an SEM photograph of a high-purity CNT tape produced in CNT production method 7 (gas supply anode) of the present invention.
FIG. 23 is a schematic view showing an arc discharge state in 2 (moving gas supply anode and cooling gas blowing) of CNT production method 7 of the present invention.
FIG. 24 is a schematic view showing an arc discharge situation in 3 (moving gas supply anode and cathode heating) of CNT production method 7 of the present invention.
FIGS. 25A and 25B are electron micrographs showing CNTs generated by arc discharge according to the fourth embodiment of the present invention, wherein FIG. 25A is an external photograph and FIG. 25B is an electron micrograph.
FIG. 26 is an electron micrograph showing CNTs generated by arc discharge according to Embodiment 4 of the present invention.
FIG. 27 is a distribution diagram showing the measurement results of the thickness of the CNT fiber shown in FIG. 25.
FIG. 28 is a schematic diagram illustrating the crystallinity of CNT according to Embodiment 4 of the present invention.
FIG. 29 is a transmission electron micrograph showing a CNT according to Embodiment 4 of the present invention.
FIG. 30 is a schematic diagram for explaining a state of tensile processing of CNT according to Embodiment 5 of the present invention.
FIG. 31 is an electron micrograph showing a side surface of a CNT according to Embodiment 5 of the present invention after being subjected to a tensile processing.
FIG. 32 is a schematic diagram illustrating a state of the CNT peeling process according to the fifth embodiment of the present invention.
FIG. 33 is an electron micrograph showing a processed surface of a CNT according to Embodiment 5 of the present invention.
FIG. 34 is a schematic diagram comparing the characteristics of CNT fibers with respect to the use of CNT according to Embodiment 6 of the present invention.
FIG. 35 is a schematic diagram showing characteristics of CNT fibers for use of CNT according to Embodiment 6 of the present invention.
FIG. 36 is a schematic diagram illustrating a filter using CNTs according to Embodiment 6 of the present invention.
FIG. 37 is a schematic diagram showing characteristics of CNT fibers for use of CNT according to Embodiment 6 of the present invention.
[Explanation of symbols]
1 CNT manufacturing device, 10 anode, 20 cathode,
30 chamber, 31 anode holder, 32 cathode holder,
33 inner wall, 34 anode moving means, 35 conducting means,
C21 tape material, T21 cathode deposit, T22 cathode soot,
T23 attached substance, T33 chamber soot, 50 anode cooling means,
60 cathode preheating means, 70 discharge gas nozzle, 80 anode moving mechanism,
90 Negative anode moving mechanism

Claims (15)

A carbon nanotube aggregate in which a plurality of carbon nanotubes are entangled and integrated, wherein the carbon nanotube aggregate contains at least 80% by volume of carbon nanotubes in a non-refined state. A carbon nanotube aggregate in which a plurality of carbon nanotubes are intertwined and integrated, wherein the carbon nanotube aggregate contains 99% or more by volume of carbon nanotubes in a non-refined state. 3. The aggregate of carbon nanotubes according to claim 2, wherein an impurity composed of a mixture of one or both of carbon and ash other than the granular or film-like carbon nanotubes is contained by 1% or less by volume. 3. The method according to claim 2, wherein impurities other than granular or film-like carbon nanotubes, which consist of one or both of carbon and ash, adhere to the surface, and the volume ratio of the carbon nanotubes becomes 80% or more as a whole. Or the carbon nanotube aggregate of 3 above. The aggregate of carbon nanotubes according to claim 3 or 4, wherein the impurities attached to the surface or inside of the product are granular with a diameter of 100 nm or less. The carbon nanotube aggregate according to any one of claims 1 to 5, wherein the carbon nanotube aggregate has flexibility. The carbon nanotube aggregate according to any one of claims 1 to 6, wherein the aggregate is generated by an arc discharge method. The carbon nanotube aggregate according to any one of claims 1 to 7, wherein a maximum distance between end portions of the plane region viewed from a predetermined direction is 1 mm or more. An apparatus for installing a carbon nanotube, which is an electron emission source on which the aggregate of carbon nanotubes according to claim 1 is installed. 10. The carbon nanotube installation device according to claim 9, wherein the carbon nanotube aggregate has an area of a plane region of 0.01 mm ² or more when viewed from a predetermined direction. An apparatus for installing a carbon nanotube, wherein the apparatus is an electric device or an electronic device on which the carbon nanotube aggregate according to claim 1 is installed. A carbon nanotube installation device, comprising a separation membrane on which the carbon nanotube aggregate according to claim 1 is installed. An apparatus for installing carbon nanotubes, which is an adsorbent or an adsorbent on which the aggregate of carbon nanotubes according to claim 1 is installed. A carbon nanotube installation apparatus, wherein the carbon nanotube aggregate according to any one of claims 1 to 8 is installed. A carbon nanotube installation device, characterized in that it is a heat radiation material on which the carbon nanotube aggregate according to any one of claims 1 to 8 is installed.

Images