JP2013018673A - Carbon nanotube aggregate where single-walled carbon nanotube and double-walled carbon nanotube are mixed at arbitrary ratio and method for producing the same - Google Patents
Carbon nanotube aggregate where single-walled carbon nanotube and double-walled carbon nanotube are mixed at arbitrary ratio and method for producing the same Download PDFInfo
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Abstract
Description
本発明は、単層カーボンナノチューブと二層カーボンナノチューブが任意比率で混合してなるカーボンナノチューブ集合体並びにその製造方法に関する。 The present invention relates to a carbon nanotube aggregate in which single-walled carbon nanotubes and double-walled carbon nanotubes are mixed at an arbitrary ratio, and a method for producing the same.
カーボンナノチューブ（以下、ＣＮＴと略す）は、その優れた機械的特性（鋼鉄の２０倍の機械強度）、銅の１０倍の熱伝導特性、および優れた電気伝導性（銅の１０００倍以上の高電流密度耐性）から、ナノ材料の代表として注目を集めている。ＣＮＴはその円筒構造が１層である単層ＣＮＴ（以下、ＳＷＣＮＴと略す）と、２層以上のグラファイト層が同心円状に重なった構造である多層ＣＮＴ（以下、ＭＷＣＮＴと略す）に大きく分類される。特に２層のグラファイト層が同心円状に重なった構造を持つものは二層ＣＮＴと呼ばれている（以下、ＤＷＣＮＴと略す）。 Carbon nanotubes (hereinafter abbreviated as CNT) have excellent mechanical properties (20 times the mechanical strength of steel), 10 times the thermal conductivity of copper, and excellent electrical conductivity (more than 1000 times higher than copper). It has attracted attention as a representative of nanomaterials from current density tolerance. CNTs are broadly classified into single-walled CNTs (hereinafter abbreviated as SWCNTs) whose cylindrical structure is a single layer and multilayered CNTs (hereinafter abbreviated as MWCNTs) where two or more graphite layers are concentrically stacked. The In particular, a structure in which two graphite layers are concentrically overlapped is called a double-walled CNT (hereinafter abbreviated as DWCNT).
ＳＷＣＮＴが優れた特性を有することは多くの理論的研究で明らかにされている。 Many theoretical studies have shown that SWCNTs have excellent properties.
しかし、実際に合成されたＳＷＣＮＴには多くの構造的欠陥が存在するため、その優れた特性が発現されにくい。それに比べ、ＤＷＣＮＴは外層のＣＮＴにたとえ欠陥があったとしても内層のＣＮＴはほぼ“完壁”な構造を保持できる。このため、ＳＷＣＮＴの有する電子部品素子としての有望な輸送特性と、ＭＷＣＮＴの有する機械的強靭性を併せもち、ＳＷＣＮＴより優れた特性を示す場合も多く知られている。例えば、ＤＷＣＮＴはＳＷＣＮＴと同等の低い電圧で優れた電界電子放出（フィールドエミッション）特性を有し、しかもＳＷＣＮＴより長寿命であり耐久性に優れるため、とくにＦＥＤその他のエレクトロニクス分野での利用に優れるＣＮＴ材料とされている。このためＤＷＣＮＴや、あるいはＳＷＣＮＴとＤＷＣＮＴが用途に合った割合で混合されたＣＮＴ集合体の効率的、且つ大量・安価に製造する方法の開発が産業的に求められている。 However, since SWCNT actually synthesized has many structural defects, it is difficult to exhibit its excellent characteristics. In contrast, DWCNT can maintain an almost “complete wall” structure even if there is a defect in the outer CNT. For this reason, there are many cases where SWCNT has a promising transport characteristic as an electronic component element and mechanical toughness which MWCNT has, and exhibits characteristics superior to SWCNT. For example, DWCNT has excellent field electron emission characteristics at a low voltage equivalent to that of SWCNT, and has a longer life and superior durability than SWCNT. It is considered as a material. For this reason, there is an industrial demand for the development of a method for producing DWCNT, or a CNT aggregate in which SWCNT and DWCNT are mixed at a ratio suitable for the application, in large quantities and at low cost.
ＣＮＴの合成には、主にアーク放電法、レーザー・アブレーション法、ＣＶＤ法（化学気相成長法。化学気相蒸着法、または化学蒸着法とも言う。）の３つの手法が用いられている。さらにＣＶＤ法には厚さ数マイクロメートル−数ナノメートルの金属層を蒸着させた基板、もしくはゼオライトやセラミックなどの担体に遷移金属微粒子を担持させた担体からＣＮＴを合成する担持触媒ＣＶＤ法、触媒微粒子を形成する前駆体化合物を直接反応管に噴霧させ反応管入口で触媒前駆体の熱分解により形成された触媒微粒子が原料ガスとキャリアガスとともに反応管内へ送り込まれ反応管内の高温区域でＣＮＴを合成する気相流動ＣＶＤ法などが挙げられる。とくに気相流動ＣＶＤ法は、スケールアップが容易であることから、ＣＮＴを工業的に大量に生産するのに最も適していると一般的に考えられる。 For the synthesis of CNTs, three methods are mainly used: an arc discharge method, a laser ablation method, and a CVD method (chemical vapor deposition method, also referred to as chemical vapor deposition method or chemical vapor deposition method). Furthermore, the CVD method is a supported catalyst CVD method or catalyst that synthesizes CNTs from a substrate on which a metal layer having a thickness of several micrometers to several nanometers is deposited, or from a support in which transition metal fine particles are supported on a support such as zeolite or ceramic. The precursor compound that forms the fine particles is sprayed directly on the reaction tube, and the catalyst fine particles formed by thermal decomposition of the catalyst precursor at the reaction tube inlet are fed into the reaction tube together with the raw material gas and the carrier gas. Examples include a vapor-phase flow CVD method for synthesis. In particular, the gas-phase flow CVD method is generally considered to be most suitable for industrially mass-producing CNTs because it is easy to scale up.
ＤＷＣＮＴの合成も上述のような方法で研究されてきている。たとえば、アーク放電法による研究例として、金属触媒入り炭素棒を陽極に用いるＤＷＣＮＴ合成法（特許文献１）、直流アークプラズマにより直径２−７ｎｍの糸状ＤＷＣＮＴ合成法（特許文献２）、含有量５０％以上の膜状ＤＷＣＮＴの製造方法（特許文献３）が公開されている。また、ＤＷＣＮＴ合成用としてアーク放電の陽極に用いる金属触媒についても研究されている。鉄（Ｆｅ）−コバルト（Ｃｏ）−ニッケル（Ｎｉ）混合触媒含有炭素棒を陽極にしてアルゴン，水素，メタン含有雰囲気中でのナノ炭素合成法（特許文献４）、水素ガスと不活性ガスの存在下で（Ｆｅ，Ｎｉ，Ｃｏ）と（亜鉛（Ｚｎ），銅（Ｃｕ），錫（Ｓｎ））の組み合わせ触媒を用いたＤＷＣＮＴ合成法（特許文献５）があげられる。さらに、アーク放電法よりも低温状態で異常グロー放電により発生したプラズマ中で水素とメタンガス雰囲気下、担持触媒塗布した基板上へのＳＷＣＮＴ（直径１ｎｍ）とＤＷＣＮＴ（直径０．６９９−１．２３６ｎｍ）の合成法（特許文献６）も公開されている。特許文献４に記載の方法によれば、主に直径２．７−５．５ｎｍのＤＷＣＮＴが７０重量％以上含むナノ炭素が合成される。そして得られたＤＷの層間隔は０．３５−０．４５ｎｍである。 The synthesis of DWCNT has also been studied by the method as described above. For example, as a research example by an arc discharge method, a DWCNT synthesis method using a carbon rod containing a metal catalyst as an anode (Patent Document 1), a thread-like DWCNT synthesis method having a diameter of 2 to 7 nm by DC arc plasma (Patent Document 2), a content of 50 % Of a film-like DWCNT manufacturing method (Patent Document 3). Also, metal catalysts used for arc discharge anodes for DWCNT synthesis have been studied. Nanocarbon synthesis method (Patent Document 4) in an atmosphere containing argon, hydrogen and methane using a carbon rod containing an iron (Fe) -cobalt (Co) -nickel (Ni) mixed catalyst as an anode, hydrogen gas and inert gas There is a DWCNT synthesis method using a combined catalyst of (Fe, Ni, Co) and (zinc (Zn), copper (Cu), tin (Sn)) in the presence (Patent Document 5). Further, SWCNT (diameter 1 nm) and DWCNT (diameter 0.699-1.236 nm) on a substrate coated with a supported catalyst in a hydrogen and methane gas atmosphere in a plasma generated by abnormal glow discharge at a lower temperature than the arc discharge method. The synthesis method (Patent Document 6) is also disclosed. According to the method described in Patent Document 4, nanocarbon mainly containing 70% by weight or more of DWCNT having a diameter of 2.7 to 5.5 nm is synthesized. The resulting DW layer spacing is 0.35-0.45 nm.
一方、担持触媒ＣＶＤ法によるＤＷＣＮＴ合成法が公開されている。 On the other hand, a DWCNT synthesis method by a supported catalyst CVD method is disclosed.
プラズマ中Ｃｏを塗布した基板上に平均内径３ｎｍ、平均外径４ｎｍのＤＷＣＮＴアレイの合成法（特許文献７）、鉄触媒を塗布した基板上に微量の水蒸気存在下、外径２−５ｎｍ、純度５０％以上の、基板に垂直に配向したＤＷＣＮＴを合成する方法（特許文献８）、メタンガスの熱分解によって金属担持触媒を設置された基板上に純度９５％以上のＤＷＣＮＴを合成する方法（特許文献９）などが公開されている。特許文献８の方法では、合成温度が１０００℃以下と低いため、合成されたＣＮＴには、ラマン分光スペクトルにおける不純物に由来するＤバンドが強く観測されている。ＳＷＣＮＴとＤＷＣＮＴのほかに多層カーボンナノチューブも存在する。また、特許文献９の方法で合成されたＣＮＴのラマン分光におけるＤバンドは大きく観察されるので、結晶性あるいは品質は低いものと推定される。 A method of synthesizing a DWCNT array having an average inner diameter of 3 nm and an average outer diameter of 4 nm on a substrate coated with Co in plasma (Patent Document 7), an outer diameter of 2-5 nm in the presence of a small amount of water vapor on a substrate coated with an iron catalyst, purity A method of synthesizing 50% or more of DWCNT oriented perpendicular to a substrate (Patent Document 8), and a method of synthesizing DWCNT of 95% or more purity on a substrate on which a metal-supported catalyst is installed by thermal decomposition of methane gas (Patent Document 8) 9) etc. are open to the public. In the method of Patent Document 8, since the synthesis temperature is as low as 1000 ° C. or lower, a D band derived from impurities in the Raman spectrum is strongly observed in the synthesized CNT. In addition to SWCNT and DWCNT, multi-walled carbon nanotubes also exist. In addition, since the D band in Raman spectroscopy of CNT synthesized by the method of Patent Document 9 is greatly observed, it is estimated that the crystallinity or quality is low.
しかしアーク放電法あるいは担持触媒ＣＶＤ法のいずれの場合も、結晶性の低いカーボンナノチューブしかできない上、連続生産は難しく工業生産には不適である。 However, in either case of the arc discharge method or the supported catalytic CVD method, only carbon nanotubes with low crystallinity can be produced, and continuous production is difficult and unsuitable for industrial production.
一方、下記のように工業的にスケールアップしやすいＤＷＣＮＴ合成法も公開されている。 On the other hand, a DWCNT synthesis method that is easy to scale up industrially as described below is also disclosed.
流動床反応器中Ｎｉ担持触媒を用いたメタン熱分解によるＣＮＴ（ＳＷＣＮＴ、ＤＷＣＮＴ、ＭＷＣＮＴ）合成法（特許文献１０）、水素とアルゴンの混合ガスをキャリアガスに、ベンゼンに溶かした混合触媒（Ｆｅ，Ｃｏ，Ｎｉ）前駆体とチオフェンを用いたＳＷＣＮＴとＤＷＣＮＴを含むＣＮＴ合成法（特許文献１１）、ＭｇＯ担持触媒を用いた、直径１−２．５ｎｍのＤＷＣＮＴの製造方法（特許文献１２）、合成反応途中で酸化剤を導入して金属担体触媒活性の回復と炭素不純物の除去を図り、メタンガスを９００℃で熱分解させることによって、直径１−３ｎｍ、含有量５０％以上、ラマン散乱分析におけるＧバンドとＤバンドの強度比ＩＧ／ＩＤ＞３０を示すＤＷＣＮＴの合成法（特許文献１３）が開示されている。 CNT (SWCNT, DWCNT, MWCNT) synthesis method by thermal decomposition of methane using Ni-supported catalyst in a fluidized bed reactor (Patent Document 10), a mixed catalyst in which a mixed gas of hydrogen and argon is dissolved in benzene in a carrier gas (Fe , Co, Ni) CNT synthesis method including SWCNT and DWCNT using thiophene and thiophene (Patent Document 11), production method of DWCNT having a diameter of 1 to 2.5 nm using MgO supported catalyst (Patent Document 12), Introducing an oxidant during the synthesis reaction to recover the catalytic activity of the metal carrier and removing carbon impurities, and thermally decomposing methane gas at 900 ° C., resulting in a Raman scattering analysis with a diameter of 1-3 nm and a content of 50% or more. A method for synthesizing DWCNT (Patent Document 13) showing an intensity ratio IG / ID> 30 of G band and D band is disclosed.
これらの方法では、いずれも多孔質担体に担持された金属触媒を使用しており、高温下では金属微粒子が担体から蒸発される恐れがあるため、反応温度は１０００℃以下に抑える必要があり、その結果ラマン散乱分析においてＧバンドとＤバンドの強度比ＩＧ／ＩＤが５０を超えるような高品質なＤＷＣＮＴを製造することはできなかった。またＣＮＴ中のＤＷＣＮＴ含有量の制御が困難であり、さらに得られたＣＮＴを固体の触媒から分離する必要があるため工業的な観点からプロセス数の増加に伴うコスト増となる、などの課題も挙げられる。これまで１０００℃以上に反応温度を設定でき、スケールアップが容易である気相流動ＣＶＤ法のＣＮＴの製造技術としては、デカリンやトルエンなどの常温で液体の炭化水素とエチレンなどの常温で気体の不飽和脂肪族炭化水素の２種類の炭素源を用いたＳＷＣＮＴ製造技術（特許文献１４および１５）が開示されているが、ＳＷＣＮＴが選択的に製造されるためＤＷＣＮＴを含むＣＮＴの製造には不適であった。 In any of these methods, a metal catalyst supported on a porous support is used, and metal fine particles may be evaporated from the support at a high temperature. Therefore, the reaction temperature must be suppressed to 1000 ° C. or lower. As a result, it was impossible to produce a high-quality DWCNT having an intensity ratio IG / ID of G band and D band exceeding 50 in Raman scattering analysis. In addition, it is difficult to control the DWCNT content in the CNT, and further, it is necessary to separate the obtained CNT from the solid catalyst, so that there is a problem that the cost increases with an increase in the number of processes from an industrial viewpoint. Can be mentioned. Up to now, the reaction temperature can be set to 1000 ° C or more, and the production technology of CNTs in the gas-phase flow CVD method, which is easy to scale up, includes hydrocarbons that are liquid at normal temperatures such as decalin and toluene, Although SWCNT production technology (Patent Documents 14 and 15) using two types of carbon sources of unsaturated aliphatic hydrocarbons is disclosed, SWCNTs are selectively produced, and thus are not suitable for the production of CNTs including DWCNT. Met.
本発明は、電子部品素子としての有望な輸送特性と機械的強靭性を併せもち透明導電材料や電子放出素子材料として有用な、単層カーボンナノチューブと二層カーボンナノチューブが混合してなる、高品質のカーボンナノチューブ集合体およびその効率的、且つ大量・安価に製造する方法を提供することを目的とする。 The present invention is a high-quality product comprising a mixture of single-walled carbon nanotubes and double-walled carbon nanotubes that have both promising transport properties and mechanical toughness as electronic component devices, and is useful as a transparent conductive material and electron-emitting device material. It is an object of the present invention to provide an aggregate of carbon nanotubes and a method for producing the carbon nanotube aggregate efficiently and in large quantities at low cost.
本発明者らは、前記の課題を解決すべく鋭意検討した結果、縦型反応管を用いた気相流動ＣＶＤ法により特定の反応条件下で高純度かつ高品質なＤＷＣＮＴとＳＷＣＮＴの任意比率の混合物を製造する方法を見出して、本発明を完成させた。
すなわち、この出願によれば、以下の発明が提供される。
As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that an arbitrary ratio of high-purity and high-quality DWCNT and SWCNT can be obtained under a specific reaction condition by a gas-phase flow CVD method using a vertical reaction tube. A method for producing the mixture was found and the present invention was completed.
That is, according to this application, the following invention is provided.
（１）気相流動ＣＶＤ法において、少なくとも水素と不活性ガスで構成される混合型キャリアガス雰囲気中、第１炭素源として常温で液体の炭化水素を、第２炭素源としてメタンを用いることを特徴とする、少なくとも単層カーボンナノチューブと二層カーボンナノチューブが混合してなるカーボンナノチューブ集合体の製造方法。 (1) In the vapor-phase flow CVD method, in a mixed carrier gas atmosphere composed of at least hydrogen and an inert gas, liquid hydrocarbon at room temperature is used as the first carbon source, and methane is used as the second carbon source. A method for producing an aggregate of carbon nanotubes characterized in that at least single-walled carbon nanotubes and double-walled carbon nanotubes are mixed.
（２）混合型キャリアガスにおける水素の含有率が１０体積％以上５０体積％以下であることを特徴とする（１）記載のカーボンナノチューブ集合体の製造方法。 (2) The method for producing a carbon nanotube aggregate according to (1), wherein the hydrogen content in the mixed carrier gas is 10% by volume or more and 50% by volume or less.
（３）混合型キャリアガスにおける不活性ガスが希ガス又は窒素であることを特徴とする（１）又は（２）記載のカーボンナノチューブ集合体の製造方法。 (3) The method for producing a carbon nanotube aggregate according to (1) or (2), wherein the inert gas in the mixed carrier gas is a rare gas or nitrogen.
（４）希ガスがアルゴン又はヘリウムであることを特徴とする（３）記載のカーボンナノチューブ集合体の製造方法。 (4) The method for producing an aggregate of carbon nanotubes according to (3), wherein the rare gas is argon or helium.
（５）第１炭素源が芳香族炭化水素であることを特徴とする（１）〜（４）のいずれかに記載のカーボンナノチューブ集合体の製造方法。 (5) The method for producing a carbon nanotube aggregate according to any one of (1) to (4), wherein the first carbon source is an aromatic hydrocarbon.
（６）芳香族炭化水素がトルエン又はベンゼンであることを特徴とする（５）記載のカーボンナノチューブ集合体の製造方法。 (6) The method for producing a carbon nanotube aggregate according to (5), wherein the aromatic hydrocarbon is toluene or benzene.
（７）第２炭素源のメタンガス流量を、同温度の気体と仮定した第１炭素源の流量の１０倍から４０倍とし、且つキャリアガス流量の５００分の１以上５分の１以下の範囲で設定することによってカーボンナノチューブ集合体中の二層カーボンナノチューブの含有率を１０重量％乃至８０重量％の範囲に調整することを特徴とする（１）〜（６）のいずれかに記載のカーボンナノチューブ集合体の製造方法。 (7) The methane gas flow rate of the second carbon source is set to be 10 to 40 times the flow rate of the first carbon source assumed to be a gas at the same temperature, and in the range of 1/500 to 1/5 of the carrier gas flow rate. The carbon according to any one of (1) to (6), wherein the content of the double-walled carbon nanotube in the aggregate of carbon nanotubes is adjusted to a range of 10 wt% to 80 wt% Manufacturing method of nanotube aggregate.
（８）二層カーボンナノチューブの平均外径が３．２±０．５ｎｍ、平均内径が２．４±０．５ｎｍ、単層カーボンナノチューブの平均直径が２．５±０．５ｎｍであり、且つラマン散乱分析におけるＧバンドとＤバンドの強度比ＩＧ／ＩＤが５０以上であることを特徴とする少なくとも単層カーボンナノチューブと二層カーボンナノチューブが混合してなるカーボンナノチューブ集合体。 (8) The average outer diameter of the double-walled carbon nanotube is 3.2 ± 0.5 nm, the average inner diameter is 2.4 ± 0.5 nm, the average diameter of the single-walled carbon nanotube is 2.5 ± 0.5 nm, and A carbon nanotube aggregate formed by mixing at least single-walled carbon nanotubes and double-walled carbon nanotubes, wherein an intensity ratio IG / ID of G band and D band in Raman scattering analysis is 50 or more.
（９）二層カーボンナノチューブの含有率が１０重量％乃至８０重量％であることを特徴とする（８）記載のカーボンナノチューブ集合体。 (9) The carbon nanotube aggregate according to (8), wherein the content of the double-walled carbon nanotube is 10% by weight to 80% by weight.
（１０）３層以上の多層カーボンナノチューブ含有率が１０重量％以下であることを特徴とする（９）記載のカーボンナノチューブ集合体。 (10) The carbon nanotube aggregate as set forth in (9), wherein the content of the multi-walled carbon nanotubes of three or more layers is 10% by weight or less.
（１１）金属含有量が５重量％以下であることを特徴とする（１０）記載のカーボンナノチューブ集合体。 (11) The carbon nanotube aggregate according to (10), wherein the metal content is 5% by weight or less.
（１２）熱重量分析における２０℃から５００℃での重量減少率が１０重量％以下であることを特徴とする（１１）記載のカーボンナノチューブ集合体。 (12) The aggregate of carbon nanotubes according to (11), wherein the weight loss rate from 20 ° C. to 500 ° C. in thermogravimetric analysis is 10% by weight or less.
（１３）（８）〜（１２）のいずれかに記載のカーボンナノチューブ集合体を加工してなる薄膜。 (13) A thin film obtained by processing the carbon nanotube aggregate according to any one of (8) to (12).
（１４）加熱手段を有し、生成物排出側にカーボンナノチューブを捕集する捕集容器、原料供給側に少なくともメタンを含むガス状炭化水素で構成される炭素源、触媒又は触媒前駆体を含む芳香族炭化水素溶液、及び少なくとも水素と不活性ガスを含むキャリアガスのための各供給路を備え、これらを原料としてカーボンナノチューブ集合体を生成せしめることができることを特徴とする縦型カーボンナノチューブ製造装置。 (14) having a heating means, a collection container for collecting carbon nanotubes on the product discharge side, and a carbon source, a catalyst or a catalyst precursor composed of gaseous hydrocarbons containing at least methane on the raw material supply side Vertical carbon nanotube production apparatus comprising an aromatic hydrocarbon solution and supply paths for a carrier gas containing at least hydrogen and an inert gas, and using these as a raw material, a carbon nanotube aggregate can be generated. .
本発明の製造方法によれば、高純度かつ高品質のＤＷＣＮＴとＳＷＣＮＴが混合されたＣＮＴ集合体を効率的、且つ大量・安価に製造することができる。 According to the production method of the present invention, a CNT aggregate in which high-purity and high-quality DWCNT and SWCNT are mixed can be produced efficiently, in large quantities and at low cost.
また、本発明方法によって得られるＣＮＴ集合体はラマン散乱分析におけるＧバンドとＤバンドの強度比ＩＧ／ＩＤが５０以上、金属触媒残存量が５重量％以下と、従来に比べて高結晶性かつ高純度であるため、優れた輸送特性と機械的強靭性を有し、透明導電材料や電子放出素子材料に有用な高品質なＣＮＴとしてエレクトロニクス分野等で多大な工業的貢献をもたらす。 In addition, the CNT aggregate obtained by the method of the present invention has a G-band to D-band intensity ratio IG / ID in a Raman scattering analysis of 50 or more and a metal catalyst residual amount of 5% by weight or less, which is highly crystalline and Because of its high purity, it has excellent transport properties and mechanical toughness, and brings a great industrial contribution in the electronics field and the like as a high-quality CNT useful for transparent conductive materials and electron-emitting device materials.
本発明の炭素源から気相流動ＣＶＤ法によりＤＷＣＮＴとＳＷＣＮＴの混合してなるＣＮＴ集合体を製造する方法は、少なくとも水素と不活性ガスで構成される混合型キャリアガス雰囲気中に、少なくとも２種類の炭素源を必要とし、第１炭素源として常温で液体の炭化水素を、第２炭素源としてメタンガスを用いることを特徴としている。 The method for producing a CNT aggregate obtained by mixing DWCNT and SWCNT from the carbon source according to the present invention by vapor-phase flow CVD method includes at least two types in a mixed carrier gas atmosphere composed of at least hydrogen and an inert gas. It is characterized by using a hydrocarbon which is liquid at normal temperature as the first carbon source and methane gas as the second carbon source.
ここでいう、「気相流動ＣＶＤ法」とは、「触媒（その前駆体を含む）及び反応促進剤を含む含炭素原料をスプレー等で霧状にして高温の加熱炉（電気炉等）に導入することによってＣＮＴを流動する気相中で合成する方法」と定義される。 As used herein, “vapor-phase flow CVD method” refers to “a carbon-containing raw material containing a catalyst (including its precursor) and a reaction accelerator, which is sprayed into a high-temperature heating furnace (such as an electric furnace). It is defined as “a method of synthesizing CNTs in a flowing gas phase by introducing them”.
また、炭素源とは、一般に「炭素原子を含む有機化合物」を意味する。
なお、本発明において、常温とは、好ましくは１５〜３５℃を指す。
The carbon source generally means “an organic compound containing a carbon atom”.
In the present invention, room temperature preferably refers to 15 to 35 ° C.
本発明において、ＣＶＤ反応場の基本的な雰囲気となるキャリアガスは、少なくとも水素と不活性ガスで構成された混合型キャリアガスであり、ＣＮＴの製造効率の観点から、キャリアガス中の水素の含有率は５体積％以上９５体積％以下が好ましく用いられ、更に好ましくは１０体積％以上５０体積％以下が好適である。 In the present invention, the carrier gas serving as the basic atmosphere of the CVD reaction field is a mixed carrier gas composed of at least hydrogen and an inert gas. From the viewpoint of the production efficiency of CNTs, the content of hydrogen in the carrier gas is included. The rate is preferably 5% by volume to 95% by volume, more preferably 10% by volume to 50% by volume.
また、上記キャリアガスにおける不活性ガスは希ガス又は窒素が好ましく用いられ、更に好ましくはアルゴン、ヘリウム又は窒素が好適である。 Further, the inert gas in the carrier gas is preferably a rare gas or nitrogen, more preferably argon, helium or nitrogen.
本発明において、第１炭素源となる炭化水素は、常温で液体の芳香族炭化水素が好ましく用いられ、この芳香族炭化水素には、単環式、縮合環式およびそれらの誘導体のいずれもが含まれる。 In the present invention, the hydrocarbon serving as the first carbon source is preferably an aromatic hydrocarbon that is liquid at room temperature, and the aromatic hydrocarbon includes any of monocyclic, condensed cyclic, and derivatives thereof. included.
本発明に使用される第１炭素源は常温で液体の条件を満たすことが必要である。このような単環式の芳香族炭化水素としては、たとえば、ベンゼン、トルエン、キシレン（オルト体、メタ体、パラ体およびこれらの混合物を含む）、トリメチルベンゼン（1,2,3-、1,2,4-、1,3,5-トリメチルベンゼンおよびこれらの混合物を含む）が例示される。本発明でとくに好ましく使用される第１炭素源は、ベンゼンまたはトルエンである。 The first carbon source used in the present invention must satisfy the liquid condition at room temperature. Examples of such monocyclic aromatic hydrocarbons include benzene, toluene, xylene (including ortho, meta, para, and mixtures thereof), trimethylbenzene (1,2,3-, 1, 2,4-, 1,3,5-trimethylbenzene and mixtures thereof). The primary carbon source particularly preferably used in the present invention is benzene or toluene.
上記第１炭素源と触媒（その前駆体を含む）及び反応促進剤を含む原料液をスプレーする方法は、特に制限はないが、上記混合型キャリアガスや水素ガス、希ガスなどを使って原料液をスプレーする二流体ノズルを用いたスプレー方式が好ましく用いられる。 The method for spraying the raw material liquid containing the first carbon source, the catalyst (including its precursor) and the reaction accelerator is not particularly limited, but the raw material is prepared using the mixed carrier gas, hydrogen gas, rare gas, or the like. A spray method using a two-fluid nozzle for spraying liquid is preferably used.
本発明において、第２炭素源となる炭化水素は第１炭素源で用いる芳香族炭化水素よりもより高い温度で熱分解するものを用いることが好ましい。このような炭化水素としては、メタンガスが挙げられ、本発明で第２炭素源として好ましく使用される。 In the present invention, it is preferable to use a hydrocarbon that is thermally decomposed at a higher temperature than the aromatic hydrocarbon used in the first carbon source as the second carbon source. Examples of such hydrocarbons include methane gas, which are preferably used as the second carbon source in the present invention.
また、第１炭素源、第２炭素源、キャリアガスの流量割合は、反応場の雰囲気としてカーボンナノチューブ製造に適するかどうかや、目標とするＣＮＴ集合体中のＤＷＣＮＴの含有率によって定められるが、第１炭素源と第２炭素源のモル比は、１：１０〜１：４０、好ましくは１：１０〜１：５０であり、且つ第２炭素源とキャリアガスの体積の比は、１：５〜１：５００、好ましくは１：１０〜１：２００、更に好ましくは１：２０〜１：４０である。このようにするとＣＮＴ集合体中のＤＷＣＮＴの含有率を１０重量％乃至８０重量％の範囲に調整することができる。 In addition, the flow rate ratio of the first carbon source, the second carbon source, and the carrier gas is determined depending on whether the reaction field atmosphere is suitable for carbon nanotube production and the target content of DWCNT in the CNT aggregate. The molar ratio of the first carbon source to the second carbon source is 1:10 to 1:40, preferably 1:10 to 1:50, and the volume ratio of the second carbon source to the carrier gas is 1: 5 to 1: 500, preferably 1:10 to 1: 200, more preferably 1:20 to 1:40. In this way, the content of DWCNT in the CNT aggregate can be adjusted to a range of 10 wt% to 80 wt%.
第２炭素源であるメタンガス流量とキャリアガス流量の割合は、ＣＮＴ集合体中のＤＷＣＮＴの含有率と特に密接に関連しており、メタンガス流量の割合を増加することによってＤＷＣＮＴの含有率が増加する傾向にある。たとえばキャリアガス流量に対してメタンガス流量を０．２体積％に設定することによってＤＷＣＮＴの含有率を１０重量％程度に、メタンガス流量を３０体積％に設定することによって、ＤＷＣＮＴの含有率を７０重量％程度にすることができる（実施例１参照）。 The ratio of the methane gas flow rate and the carrier gas flow rate as the second carbon source is particularly closely related to the DWCNT content rate in the CNT aggregate, and increasing the methane gas flow rate rate increases the DWCNT content rate. There is a tendency. For example, by setting the methane gas flow rate to 0.2% by volume with respect to the carrier gas flow rate, the DWCNT content rate is set to about 10% by weight, and by setting the methane gas flow rate to 30% by volume, the DWCNT content rate is set to 70% by weight. % (See Example 1).
また、第１炭素源と第２炭素源を反応器への導入方法は、副反応制御の点からみて、第１炭素源が導入される前に第２炭素源を導入してはならず、好ましくは第１炭素源と第２炭素源を同時に反応器に導入するのがよい。 In addition, the method of introducing the first carbon source and the second carbon source into the reactor should not introduce the second carbon source before the first carbon source is introduced from the viewpoint of side reaction control. Preferably, the first carbon source and the second carbon source are introduced into the reactor at the same time.
また、第１炭素源および第２炭素源は反応を迅速、且つ、均一に行わせるために、キャリアガスと共に反応器に導入するのが好ましい。 The first carbon source and the second carbon source are preferably introduced into the reactor together with the carrier gas in order to perform the reaction quickly and uniformly.
第１炭素源、第２炭素源、キャリアガスの流量を合わせたトータル流量は、特に制限はなく、反応器の容量および形状等に応じて適宜選ばれる。 The total flow rate that combines the flow rates of the first carbon source, the second carbon source, and the carrier gas is not particularly limited, and is appropriately selected according to the capacity and shape of the reactor.
本発明によりＣＮＴ集合体を製造するには、たとえば、触媒と、反応促進剤と、前記第１炭素源と、第２炭素源および好ましくはキャリアガスのそれぞれをあるいはこれらを混合して得られる原料混合物を反応器内における８００〜１２００℃の温度に維持された反応領域に供給すればよい。 In order to produce a CNT aggregate according to the present invention, for example, a catalyst, a reaction accelerator, the first carbon source, a second carbon source, and preferably a carrier gas, or a raw material obtained by mixing them, is used. What is necessary is just to supply a mixture to the reaction zone maintained at the temperature of 800-1200 degreeC in a reactor.
本発明で使用する触媒は金属の種類やその形態の違いに特に制限されるものではないが、遷移金属化合物又は遷移金属超微粒子が好ましく用いられる。 The catalyst used in the present invention is not particularly limited by the kind of metal or the form thereof, but a transition metal compound or transition metal ultrafine particles are preferably used.
前記遷移金属化合物は、反応器内で分解することにより、触媒としての遷移金属微粒子を生成することができ、反応器内における８００〜１２００℃の温度に維持された反応領域に、気体若しくは金属クラスタの状態で供給されるのが好ましい。 The transition metal compound can be decomposed in a reactor to produce fine particles of a transition metal as a catalyst. In the reaction region maintained at a temperature of 800 to 1200 ° C. in the reactor, a gas or a metal cluster It is preferable to be supplied in the state of
前記遷移金属化合物としては、例えば、有機遷移金属化合物、無機遷移金属化合物等を挙げることができる。前記有機遷移金属化合物としては、フェロセン、コバルトセン、ニッケロセン、鉄カルボニル、アセチルアセトナート鉄、オレイン酸鉄等を挙げることができ、より好ましくはフェロセンである。前記無機遷移金属化合物としては塩化鉄等を挙げることができる。 Examples of the transition metal compound include organic transition metal compounds and inorganic transition metal compounds. Examples of the organic transition metal compound include ferrocene, cobaltocene, nickelocene, iron carbonyl, iron acetylacetonate, and iron oleate, and ferrocene is more preferable. Examples of the inorganic transition metal compound include iron chloride.
前記遷移金属超微粒子としては、鉄、コバルト、ニッケル、スカンジウム、チタン、バナジウム、クロム、マンガン等を挙げることができ、中でもより好ましいのは鉄、コバルト、ニッケルである。 Examples of the transition metal ultrafine particles include iron, cobalt, nickel, scandium, titanium, vanadium, chromium, and manganese. Among these, iron, cobalt, and nickel are more preferable.
本発明に係る反応促進剤としては、硫黄化合物が好ましく用いられる。この硫黄化合物は、硫黄原子を含有し、触媒としての遷移金属と相互作用して、ＣＮＴの生成を促進させることができる。 A sulfur compound is preferably used as the reaction accelerator according to the present invention. This sulfur compound contains a sulfur atom and can interact with a transition metal as a catalyst to promote the generation of CNTs.
前記硫黄化合物としては、有機硫黄化合物、無機硫黄化合物を挙げることができる。前記有機硫黄化合物としては、例えば、チアナフテン、ベンゾチオフェン、チオフェン等の含硫黄複素環式化合物を挙げることができ、より好ましくはチオフェンである。前記無機硫黄化合物としては、例えば、硫化水素等を挙げることができる。 Examples of the sulfur compound include organic sulfur compounds and inorganic sulfur compounds. Examples of the organic sulfur compound include sulfur-containing heterocyclic compounds such as thianaphthene, benzothiophene, and thiophene, and thiophene is more preferable. Examples of the inorganic sulfur compound include hydrogen sulfide.
本発明に係る主にＤＷＣＮＴとＳＷＣＮＴで構成されるＣＮＴ集合体は、ＤＷＣＮＴの平均外径が３．２±０．５ｎｍ、平均内径が２．４±０．５ｎｍ、ＳＷＣＮＴの平均直径が２．５±０．５ｎｍであり、且つラマン散乱分析におけるＧバンドとＤバンドの強度比ＩＧ／ＩＤが５０以上であることを特徴とする。 The CNT aggregate mainly composed of DWCNT and SWCNT according to the present invention has an average outer diameter of DWCNT of 3.2 ± 0.5 nm, an average inner diameter of 2.4 ± 0.5 nm, and an average diameter of SWCNT of 2. It is 5 ± 0.5 nm, and the intensity ratio IG / ID of G band and D band in Raman scattering analysis is 50 or more.
ここで、ラマン散乱分析におけるＧバンドとは、１５９０ｃｍ−１付近に観測される振動モードでグラファイトのラマン活性モードと同種の振動モードであると考えられている。一方、Ｄバンドとは１３５０ｃｍ−１付近に観測される振動モードである。グラファイトはこの振動数領域に巨大なフォノン状態密度をもつが、ラマン活性ではないためにＨＯＰＧ（高配向熱分解黒鉛）などの結晶性の高いグラファイトでは観測されない。しかし欠陥が導入されると運動量保存則に破れが生じ、ラマンピークとなって観測される。そのためこの種のピークは欠陥由来のピークとして考えられる。欠陥由来であるため結晶性の低いアモルファスやナノ粒子において、強い強度で観測されることが知られている。したがって、これらＧバンドとＤバンドに由来するピークの強度比ＩＧ／ＩＤはＣＮＴの構造や純度の指標として客観性が高く、最も信頼できる純度評価法の一つと言える。ＩＧ／ＩＤの値が高いほど、高純度で高品質なものとされる。 Here, the G band in the Raman scattering analysis is a vibration mode observed in the vicinity of 1590 cm −1 and is considered to be a vibration mode similar to the Raman active mode of graphite. On the other hand, the D band is a vibration mode observed near 1350 cm −1 . Graphite has a huge phonon density of states in this frequency range, but is not observed in highly crystalline graphite such as HOPG (highly oriented pyrolytic graphite) because it is not Raman active. However, when a defect is introduced, the momentum conservation law is broken, and a Raman peak is observed. Therefore, this type of peak is considered as a defect-derived peak. It is known to be observed with strong intensity in amorphous and nanoparticles with low crystallinity because they are derived from defects. Therefore, the intensity ratio IG / ID of peaks derived from these G and D bands is highly objective as an index of the structure and purity of CNT, and can be said to be one of the most reliable purity evaluation methods. The higher the value of IG / ID, the higher the purity and quality.
本発明の背景技術の項で述べたように、いずれの方法によって製造されたＤＷＣＮＴにおいても、ラマンスペクトルにおけるＧバンドとＤバンドの強度比ＩＧ／ＩＤは高くてもせいぜい３０程度であり、構造欠陥や不純物を多く包含するものであって、高品質なものとはいえなかった。 As described in the background section of the present invention, in any DWCNT produced by any method, the intensity ratio IG / ID between the G band and the D band in the Raman spectrum is at most about 30, and structural defects It contains a lot of impurities and was not high quality.
これに対して、本発明に係るＤＷＣＮＴとＳＷＣＮＴが混合してなるＣＮＴ集合体は、従来のものとは異なり、その直径が２〜４ｎｍ程度の範囲内にあり、かつ上記ＩＧ／ＩＤは少なくとも５０以上、より好ましくは１００以上を有するものであり、その高結晶性のために、従来のものに比し、電気的、力学的特性が優れていると考えられる。 On the other hand, the CNT aggregate formed by mixing DWCNT and SWCNT according to the present invention is different from the conventional CNT aggregate and has a diameter in the range of about 2 to 4 nm, and the IG / ID is at least 50 As described above, more preferably 100 or more, and due to its high crystallinity, it is considered that the electrical and mechanical characteristics are superior to those of the conventional one.
殊に、ＤＷＣＮＴの含有量が全体の１０重量％以上、とくに７０〜８０重量％程度を占めるカーボンナノチューブ集合体は不均一な直径分布を有するＳＷＣＮＴや直径の太いＣＮＴに比べて、非常に高い導電性と機械的強靭性を与えることから、透明導電材料や電子放出素子材料などとしてエレクトロニクス分野等で多大な工業的貢献をもたらす。また、３層以上のＭＷＣＮＴの含有量は材料特性の劣化を防ぐ観点から１０重量％以下であることが好ましい。 In particular, the aggregate of carbon nanotubes having a DWCNT content of 10% by weight or more, particularly about 70 to 80% by weight, has a very high conductivity compared to SWCNTs having a non-uniform diameter distribution and CNTs having a large diameter. It gives a great industrial contribution in the electronics field etc. as a transparent conductive material and an electron-emitting device material. Moreover, it is preferable that content of 3 or more layers of MWCNT is 10 weight% or less from a viewpoint of preventing deterioration of a material characteristic.
さらに、本発明のＣＮＴ集合体は熱重量分析における室温（２０℃程度）から５００℃までの重量減少率が１０重量％以下であることが好ましく、このようなＣＮＴ集合体はアモルファスカーボンなどの不純物含有量が少なく品質の高い単層と二層カーボンナノチューブの混合物集合体である。 Further, the CNT aggregate of the present invention preferably has a weight reduction rate of 10% by weight or less from room temperature (about 20 ° C.) to 500 ° C. in thermogravimetric analysis. Such a CNT aggregate is an impurity such as amorphous carbon. It is a mixed aggregate of single-walled and double-walled carbon nanotubes with low content and high quality.
以下、本発明を実施例に基づきさらに具体的に説明する。なお、以下の実施例は、本願発明の理解を容易にするためのものであり、これらの実施例に制限されるものではない。すなわち、本願発明の技術思想に基づく変形、実施態様、他の例は、本願発明に含まれるものである。
［直径および層数評価法］
透過型電子顕微鏡：Ｔｏｐｃｏｍ社ＥＭ−００２Ｂ／ＵＨＲ、加速電圧１２０ｋＶでＣＮＴを観察し、１００本のＣＮＴの直径（ＤＷＣＮＴの場合には内層と外層の直径）と層数を測定して統計的に解析した。なお、以下の実施例において単純にＳＷ含有率、ＤＷ含有率等と表記した場合には、１００本中のＳＷＣＮＴやＤＷＣＮＴの本数の割合のことを示す。
［ラマン散乱分析］
レーザーラマン分光光度計として日本分光株式会社製ＮＲＳ−２１００レーザーラマン分光光度計を使用し、アルゴンガスレーザー（波長５１４．５ｎｍ）を励起光源として測定した。
［光吸収分光分析］
分散剤としてコール酸ナトリウムを使って重水にＣＮＴを分散させ、１２７６００Ｇで遠心分離したのち、上澄み溶液を日立製作所製Ｕ−４１００型で光吸収スペクトルを測定した。
［熱重量分析］
株式会社リガク社製、示差熱天秤ＴＧ８１２０を用い、空気流量１００ｃｃ／ｍｉｎ、昇温速度５℃／ｍｉｎで２０℃から９００℃まで重量減少曲線を測定した。
［透明導電性評価］
分散剤としてカルボキシメチルセルロースナトリウム塩を用いて、ＣＮＴの濃度が０．０９重量％のＣＮＴ分散水溶液を調製し、ＰＥＴフィルム（１５ｃｍ×１０ｃｍ、光透過率は９１％であった）上にバーコーター（Ｎｏ．３〜１０）を用いて塗布成膜したのち、得られる膜を水で洗浄してＣＮＴ膜を得た。このＣＮＴ膜の導電性は、表面抵抗値を（株）ダイアインスツルメンツ社製抵抗率計ロレスタＧＰ ＭＣＰ−Ｔ６００を用いて測定した。また透過率は日本電色工業株式会社製ヘイズメーターＮＤＨ４０００を使用してＣＮＴ膜が基材上に密着した状態で基材ごと測定した。
Hereinafter, the present invention will be described more specifically based on examples. In addition, the following examples are for facilitating the understanding of the present invention, and are not limited to these examples. That is, modifications, embodiments, and other examples based on the technical idea of the present invention are included in the present invention.
[Diameter and number of layers evaluation method]
Transmission electron microscope: Topcom EM-002B / UHR, observing CNTs at an acceleration voltage of 120 kV, measuring the diameter of 100 CNTs (in the case of DWCNT, the diameters of the inner and outer layers) and the number of layers statistically Analyzed. In the following examples, when simply described as SW content, DW content, etc., it indicates the ratio of the number of SWCNTs or DWCNTs out of 100.
[Raman scattering analysis]
An NRS-2100 laser Raman spectrophotometer manufactured by JASCO Corporation was used as a laser Raman spectrophotometer, and an argon gas laser (wavelength 514.5 nm) was measured as an excitation light source.
[Light absorption spectroscopy]
After dispersing CNT in heavy water using sodium cholate as a dispersant and centrifuging at 127600 G, the light absorption spectrum of the supernatant solution was measured with a U-4100 model manufactured by Hitachi.
[Thermogravimetric analysis]
Using a differential thermal balance TG8120 manufactured by Rigaku Corporation, a weight reduction curve was measured from 20 ° C. to 900 ° C. at an air flow rate of 100 cc / min and a heating rate of 5 ° C./min.
[Transparent conductivity evaluation]
A CNT-dispersed aqueous solution having a CNT concentration of 0.09 wt% was prepared using carboxymethylcellulose sodium salt as a dispersant, and a bar coater (15 cm × 10 cm, light transmittance was 91%) on a PET film (15% × 10 cm). No. 3 to 10) were used for coating and film formation, and the resulting film was washed with water to obtain a CNT film. The conductivity of the CNT film was measured using a resistivity meter Loresta GP MCP-T600 manufactured by Dia Instruments Co., Ltd. Moreover, the transmittance | permeability was measured for each base material in the state which the CNT film | membrane closely_contact | adhered on the base material using the Nippon Denshoku Industries Co., Ltd. haze meter NDH4000.
＜実施例１＞
図１に示すような、縦型のＣＮＴ製造装置を使用して本発明のＣＮＴ集合体を製造した。
<Example 1>
The CNT aggregate of the present invention was manufactured using a vertical CNT manufacturing apparatus as shown in FIG.
本装置は電気炉１、内径５２ｍｍ、外径６０ｍｍ、長さ１２００ｍｍ、内有効加熱長さ６００ｍｍのムライト製反応管２、液状原料スプレー３、スプレーガス流量計４、第１キャリアガス流量計５、第２キャリアガス流量計６、マイクロフィーダー７、回収フィルター８、第２炭素源流量計９、ガス混合器１０、で構成されている。 The apparatus comprises an electric furnace 1, a mullite reaction tube 2 having an inner diameter of 52 mm, an outer diameter of 60 mm, a length of 1200 mm, and an inner effective heating length of 600 mm, a liquid raw material spray 3, a spray gas flow meter 4, a first carrier gas flow meter 5, It comprises a second carrier gas flow meter 6, a microfeeder 7, a recovery filter 8, a second carbon source flow meter 9, and a gas mixer 10.
マイクロフィーダー７には、第１炭素源となるトルエン：有機遷移金属化合物であるフェロセン：有機硫黄化合物であるチオフェンの混合比が、重量比で１００：４：１の原料液を貯留し、他方第２炭素源としてメタンを使用し、第２炭素源流量計９、ガス混合器１０を経て、流量制御した。 The microfeeder 7 stores a raw material liquid having a mixing ratio of toluene: organic transition metal compound ferrocene: organic sulfur compound thiophene: 100: 4: 1 as a first carbon source, Methane was used as the two carbon source, and the flow rate was controlled via the second carbon source flow meter 9 and the gas mixer 10.
水素ガスを第１キャリアガスおよびスプレーガス、アルゴンを第２キャリアガスとしてスプレーガス流量計４、キャリアガス流量計５および６を用いて、水素：アルゴンの混合比を体積比で３：７、合計流量を流量３Ｌ／ｍｉｎに制御した混合型キャリアガスとして流通させ、１２００℃に加熱された電気炉中の反応管２に、上記原料液を７．５μＬ／ｍｉｎの流速で３時間スプレーすることによって流動気相ＣＶＤ合成を行った。生成物は回収フィルター８で捕集した。第２炭素源のメタンガス流量を０−９０ｓｃｃｍに制御して製造した生成物の時間当たりの収量、ＩＧ／ＩＤ比、ＴＥＭ観察の結果によって得られたＳＷＣＮＴの含有率と、ＤＷＣＮＴの含有率を表１に示す。 Using a spray gas flow meter 4 and carrier gas flow meters 5 and 6 with hydrogen gas as the first carrier gas and spray gas and argon as the second carrier gas, the hydrogen: argon mixture ratio is 3: 7 in volume ratio, total By flowing as a mixed carrier gas whose flow rate is controlled to 3 L / min and spraying the raw material liquid on the reaction tube 2 in an electric furnace heated to 1200 ° C. at a flow rate of 7.5 μL / min for 3 hours. Fluidized gas phase CVD synthesis was performed. The product was collected with a collection filter 8. Table 2 shows the yield per hour, the IG / ID ratio, the SWCNT content and the DWCNT content obtained by controlling the methane gas flow rate of the second carbon source to 0-90 sccm. It is shown in 1.
ＣＮＴの時間当たりの収量はメタンガス流量の増加とともに高くなり、６０ｓｃｃｍで最大となった。 The yield per hour of CNT increased with increasing methane gas flow rate and reached a maximum at 60 sccm.
図２ａは、透過型電子顕微鏡（ＴＥＭ）で観察されたＳＷＣＮＴ集合体（メタンガス流量１０ｓｃｃｍでの生成物）であり、図２ｂはＴＥＭで観察されたＳＷとＤＷ集合体（メタンガス流量３０ｓｃｃｍでの生成物）であり、図２ｃはＳＷ，ＤＷ、ＭＷＣＮＴ集合体（メタンガス流量９０ｓｃｃｍでの生成物）である。図２ｂにおいてＳＷＣＮＴは円で囲まれている。図２ｃにおいてＭＷＣＮＴは○で、ＳＷＣＮＴは破線で囲まれている。ＴＥＭ写真によれば、実際には、得られた生成物はほとんどＳＷとＤＷＣＮＴであり、三層以上のＭＷＣＮＴも確認されたが、その量はわずか１０重量％以下であった。 FIG. 2a is a SWCNT aggregate (product at a methane gas flow rate of 10 sccm) observed by a transmission electron microscope (TEM), and FIG. 2b is a SW and DW aggregate observed at a TEM (production at a methane gas flow rate of 30 sccm). FIG. 2c shows a SW, DW, and MWCNT aggregate (product at a methane gas flow rate of 90 sccm). In FIG. 2b, SWCNTs are circled. In FIG. 2c, MWCNT is circled and SWCNT is surrounded by a broken line. According to the TEM photograph, the products obtained were actually SW and DWCNT, and three or more layers of MWCNT were also confirmed, but the amount was only 10% by weight or less.
ＴＥＭ写真をもってＳＷＣＮＴとＤＷＣＮＴの割合及びそれぞれの直径を測定した。ＳＷＣＮＴの含有率はメタンガス流量に依存し、メタン増加につれて９５％から３６％に低下し、逆にＤＷＣＮＴ含有率は５％から６３％に増えた。図３に示すように、メタンガス流量の変化によらずカーボンナノチューブの直径はほぼ一定であり、ＳＷＣＮＴの平均直径は２．５ｎｍで、ＤＷＣＮＴの平均外形は３．２ｎｍ、平均内径は２．４ｎｍであった。これらの値からメタンガス流量によって制御できるＤＷＣＮＴの含有率を重量パーセント表示すると１０重量％〜８０重量％であった。 The ratio of SWCNT and DWCNT and the diameter of each were measured with a TEM photograph. The SWCNT content depends on the methane gas flow rate, and decreases from 95% to 36% as methane increases, and conversely, the DWCNT content increases from 5% to 63%. As shown in FIG. 3, the diameter of the carbon nanotube is almost constant regardless of the change in the methane gas flow rate, the average diameter of SWCNT is 2.5 nm, the average outer shape of DWCNT is 3.2 nm, and the average inner diameter is 2.4 nm. there were. From these values, the content of DWCNT that can be controlled by the methane gas flow rate is 10 wt% to 80 wt% in terms of weight percent.
図４にあるようにラマン分光では、１００ｃｍ−１に主なＲＢＭピークがあり、直径約２．４８ｎｍのＳＷＣＮＴに対応する。この位置はメタンガス流量が３０ｓｃｃｍまで変わらず、より多くのメタンの添加では、ＤＷＣＮＴ割合の増加でピークの強度が弱くなった。またいずれの場合１５９０ｃｍ−１における強いＧバンドに比べ１３００ｃｍ−１付近におけるＤバンドのピークは非常に弱い。得られたＣＮＴのＩＧ／ＩＤ比はいずれも６０以上であった。 As shown in FIG. 4, in Raman spectroscopy, there is a main RBM peak at 100 cm −1 , which corresponds to SWCNT having a diameter of about 2.48 nm. At this position, the flow rate of methane gas did not change up to 30 sccm, and when more methane was added, the intensity of the peak became weaker as the DWCNT ratio increased. The peak of the D band at 1300cm around -1 compared to strong G band in the case 1590 cm -1 in either very weak. The obtained CNT had an IG / ID ratio of 60 or more.
さらに図５にあるようにＵＶ吸収スペクトルでは、メタン流量変化によるＳ２２吸収ピークの変化はわずかであり、ＳＷＣＮＴの直径はほぼ一定であることを反映している。これは上記のＴＥＭ観察の結果と一致している。 Further, as shown in FIG. 5, in the UV absorption spectrum, the change in the S22 absorption peak due to the change in the methane flow rate is slight, reflecting that the SWCNT diameter is almost constant. This is consistent with the results of the above TEM observation.
熱重量測定により、図６のようにＣＮＴ集合体は５００℃までの重量減少率は２−６重量％以下であり、９００℃までの重量減少率から計算された金属含有率はいずれも４重量％以下であった。 As shown in FIG. 6, the weight loss rate up to 500 ° C. is 2-6% by weight or less, and the metal content calculated from the weight reduction rate up to 900 ° C. is 4%. % Or less.
＜実施例２＞
マイクロフィーダー７に貯留する原料液におけるトルエン：有機遷移金属化合物であるフェロセン：有機硫黄化合物であるチオフェンの混合比が、重量比で１００：２：０．５、キャリアガスを水素：窒素の混合比が、体積比で５：５の混合型キャリアガスにした以外は、実施例１と同様にして実験を行った。結果を表２に示す。
<Example 2>
The mixing ratio of toluene: organic transition metal compound ferrocene: organic sulfur compound thiophene in the raw material liquid stored in the microfeeder 7 is 100: 2: 0.5 by weight ratio, and the carrier gas is a mixing ratio of hydrogen: nitrogen. However, the experiment was conducted in the same manner as in Example 1 except that the mixed carrier gas was 5: 5 by volume. The results are shown in Table 2.
ＣＮＴの時間当たりの収量はメタンガス流量の増加とともに高くなったが、触媒量が少ないため実施例１で得られた収量より低下した。メタンガス流量の増加につれてＳＷＣＮＴの含有率は８４％から５２％に低下し、逆にＤＷＣＮＴ含有率は１６％から４８％に増えた。 The yield per hour of CNT increased with an increase in the methane gas flow rate, but was lower than the yield obtained in Example 1 due to the small amount of catalyst. As the methane gas flow rate increased, the SWCNT content decreased from 84% to 52%, and conversely, the DWCNT content increased from 16% to 48%.
図７のように、ＴＥＭ観察により得られたＳＷＣＮＴとＤＷＣＮＴの直径はほぼ一定であり、ＳＷＣＮＴの平均直径は２．５ｎｍで、ＤＷＣＮＴの平均外径は３．３ｎｍ、平均内径は２．２ｎｍであった。これらの値からメタンガス流量によって制御できるＤＷＣＮＴの含有率を重量パーセント表示すると３０重量％〜７０重量％であった。 As shown in FIG. 7, the diameters of SWCNT and DWCNT obtained by TEM observation are almost constant, the average diameter of SWCNT is 2.5 nm, the average outer diameter of DWCNT is 3.3 nm, and the average inner diameter is 2.2 nm. there were. From these values, the content of DWCNT that can be controlled by the methane gas flow rate is 30 wt% to 70 wt% when expressed in weight percent.
図８のラマン測定の結果、１００ｃｍ−１におけるＲＢＭピーク（直径２．４８ｎｍのＳＷＣＮＴに対応）は一定であり、ＣＮＴのＩＧ／ＩＤ比はいずれも６０以上であった。 As a result of the Raman measurement in FIG. 8, the RBM peak at 100 cm −1 (corresponding to SWCNT having a diameter of 2.48 nm) was constant, and the IG / ID ratio of each CNT was 60 or more.
熱重量測定によると、ＣＮＴ集合体は５００℃までの重量減少率は４−６重量％であり、９００℃までの重量減少率から計算された金属含有率はいずれも２重量％以下であった。 According to thermogravimetry, the weight loss rate up to 500 ° C. of the CNT aggregate was 4-6% by weight, and the metal content calculated from the weight loss rate up to 900 ° C. was less than 2% by weight. .
＜実施例３＞
マイクロフィーダー７に貯留する原料液におけるトルエン：有機遷移金属化合物であるフェロセン：有機硫黄化合物であるチオフェンの混合比が、重量比で１００：４：２、キャリアガスを水素：ヘリウムの混合比が、体積比で１：９の混合型キャリアガスにしたにした以外は、実施例１と同様にして実験を行った。結果を表３に示す。
<Example 3>
The mixing ratio of toluene: organic transition metal compound ferrocene: organic sulfur compound thiophene in the raw material liquid stored in the microfeeder 7 is 100: 4: 2 by weight, and the carrier gas is a hydrogen: helium mixing ratio. The experiment was performed in the same manner as in Example 1 except that the mixed carrier gas was in a volume ratio of 1: 9. The results are shown in Table 3.
ＣＮＴ収量はメタンガス流量の増加とともに高くなったが、実施例１より低下した。ＴＥＭ観察によりメタンガス流量の増加につれてＳＷＣＮＴの含有率は８２％から５６％に低下し、逆にＤＷＣＮＴ含有率は１８％から４４％に増えた。 The CNT yield increased with increasing methane gas flow, but decreased from Example 1. According to TEM observation, the SWCNT content decreased from 82% to 56% as the methane gas flow rate increased, and conversely, the DWCNT content increased from 18% to 44%.
図９のように、ＳＷＣＮＴの平均直径は２．２ｎｍでほぼ一定であったものの、ＤＷＣＮＴはメタン量の増加につれて、外径は３．９ｎｍから２．８ｎｍに、内径は２．９ｎｍから１．９ｎｍに細くなる傾向が見られた。平均外径は３．３ｎｍ、平均内径は２．２ｎｍとなった。これらの値からメタンガス流量によって制御できるＤＷＣＮＴの含有率を重量パーセント表示すると３０重量％〜６５重量％であった。 As shown in FIG. 9, although the average diameter of SWCNT was almost constant at 2.2 nm, the outer diameter of DWCNT increased from 3.9 nm to 2.8 nm and the inner diameter increased from 2.9 nm to 1.nm as the amount of methane increased. There was a tendency to narrow to 9 nm. The average outer diameter was 3.3 nm, and the average inner diameter was 2.2 nm. From these values, the content of DWCNT that can be controlled by the methane gas flow rate is 30% to 65% by weight when expressed in weight percent.
ラマン測定の結果、図１０のようにＣＮＴのＩＧ／ＩＤ比はいずれも６０以上であった。ただし、低いメタン流量においてＲＢＭピークは低波数側にも見られ、より太いＣＮＴの存在を示唆する結果を得た。ＴＥＭ観察の結果からおもに直径の太いＤＷＣＮＴが生成したためであることを確認した。 As a result of Raman measurement, the IG / ID ratio of CNTs was 60 or more as shown in FIG. However, the RBM peak was also seen on the low wavenumber side at a low methane flow rate, and the result suggesting the presence of thicker CNTs was obtained. From the result of TEM observation, it was confirmed that this was mainly due to the generation of DWCNT having a large diameter.
熱重量測定によると、ＣＮＴ集合体は５００℃までの重量減少率は３−６％であり、９００℃までの重量減少率から計算された金属含有率はいずれも３％以下であった。 According to thermogravimetry, the weight loss rate up to 500 ° C. of the CNT aggregate was 3-6%, and the metal content calculated from the weight loss rate up to 900 ° C. was 3% or less.
＜実施例４＞
実施例１で用いたメタンガス流量１０ｓｃｃｍ（ＤＷＣＮＴ含有率７％）のＣＮＴ集合体と、メタンガス流量６０ｓｃｃｍ（ＤＷＣＮＴ含有率４２％）のＣＮＴ集合体とを用いて、ＣＮＴ膜の透明導電性を測定したところ、良好な透明導電性を示した。ＤＷＣＮＴの含有量が多いほど優れた透明導電性を示す結果となった（図１１）。
<Example 4>
The transparent conductivity of the CNT film was measured using the CNT aggregate having a methane gas flow rate of 10 sccm (DWCNT content of 7%) and the CNT aggregate having a methane gas flow rate of 60 sccm (DWCNT content of 42%) used in Example 1. However, it showed good transparent conductivity. The higher the DWCNT content, the better the transparent conductivity (FIG. 11).
本発明の製造装置を用いた製造方法にて得られるカーボンナノチューブ集合体は、任意の比率で高品質かつ高純度の単層と二層のカーボンナノチューブを有し、カーボンナノチューブの本来の優れた電気・熱伝導性、及び機械的性質を発現でき、従来の炭素繊維よりも高強度、高熱伝導性、高電気伝導性を有しており、透明導電膜、電解電子放出デバイス、などの用途に好適である。 The aggregate of carbon nanotubes obtained by the production method using the production apparatus of the present invention has high-quality and high-purity single-walled and double-walled carbon nanotubes at an arbitrary ratio, and the carbon nanotube original excellent electric -It can exhibit thermal conductivity and mechanical properties, has higher strength, higher thermal conductivity, and higher electrical conductivity than conventional carbon fiber, and is suitable for applications such as transparent conductive films and electrolytic electron emission devices. It is.
１ 電気炉
２ 反応管
３ 液状原料スプレー
４ スプレーガス流量計
５ 第１キャリアガス流量計
６ 第２キャリアガス流量計
７ マイクロフィーダ―
８ 回収フィルター
９ 第２炭素源流量計
１０ ガス混合器
DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Reaction tube 3 Liquid raw material spray 4 Spray gas flow meter 5 1st carrier gas flow meter 6 2nd carrier gas flow meter 7 Micro feeder
8 Recovery filter 9 Second carbon source flow meter 10 Gas mixer
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