JP4238024B2 - Method for producing composite carbonaceous substrate - Google Patents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
Description
【０００１】
【発明の属する技術分野】
本発明はリチウム電池などの各種電池、二重層コンデンサなどの各種キャパシタの電極、集電体、等として使用される炭素質基板の製造方法に関する。
【０００２】
【従来の技術】
炭素材料、グラファイト材料は優れた耐熱性、耐薬品性、高熱伝導性、高電気伝導性のため工業材料として重要な位置をしめ、電気伝導体、電極、集電体、放熱材料、耐熱シール材、ガスケット、発熱体、等として広く使用されている。
近年気相成長炭素繊維が注目を集め、なかでもカーボンナノチューブ（ＣＮＴ）と呼ばれる気相成長炭素繊維はその優れた物性のゆえに、近年非常に注目されている。気相成長炭素繊維の製造法としてはアーク放電法、レーザーアブレーション法、ＣＶＤ法などが知られており多くの特許が出願されている。ＣＮＴは極めて微細な炭素繊維であるため、その取り扱いは極めて困難であり、その優れた性質をエレクトロニクスの分野で生かすには何らかの形でＣＮＴを取り扱いやすい形にする必要があった。しかし、気相成長炭素繊維はその名の通り真空中で作製されるため、必要な部分のみに、一定方向にＣＮＴを成長させる事は極めて困難であった。また気相でのＣＮＴの作製はＣＮＴのみでなく必ずアモルファス炭素の生成が起きるためそれを取り除くこともまた困難であった。
それに対して、最近メタノールやブタノールなどの液中でシリコン基板上にＣＮＴを作製する方法が論文発表された。
【０００３】
【特許文献１】
特開２００２−６９６４３
【０００４】
【特許文献２】
特開２００２−１８０２５２
【０００５】
【特許文献３】
特開２００２−２２０２１４
【０００６】
【特許文献４】
特開２０００−８６２１７
【０００７】
【特許文献５】
特開平０６−３２５６２３
【０００８】
【特許文献６】
特開平０７−２１６６６０
【０００９】
【特許文献７】
特開平０８−２３１２１０
【００１０】
【特許文献８】
特開平０９−２２１３０９
【００１１】
【非特許文献１】
Y. Zhang, et, al., Jpn. J. Appl. Phys. Vol. 41, L408(2002)
【００１２】
【非特許文献２】
Y. Zhang, et, al., J. Mater. Res., Vol. 17, 9, 2457(2002)
【００１３】
【発明が解決しようとする課題】
本発明は、炭素質材料の表面に液体中で炭素質繊維を成長させる事を特徴とする複合炭素質基板の製造方法に関する。我々は液体中での炭素繊維の作製法を種々検討し、炭素質材料の表面にＣＮＴを成長させる新たな複合炭素基板の作製法を開発し、本発明を成すに至った。この手法で開発された炭素電極は極めて大きな表面積を有し、リチウム電池などの各種電池、二重層コンデンサなどの各種キャパシタの電極、集電体、ＦＥＤ（フィールド エミッション ディスプレイ）用電極、あるいはガス吸着用基板、等として広範囲な用途に使用する事が出来る。
【００１４】
【課題を解決するための手段】
（１）本発明の第一は、炭素質基板面に金属触媒を担持し、該炭素質基板を５００〜１２００℃の温度で加熱して炭素質基板上に炭素繊維を成長させる事を特徴とし、当該炭素質基板が多孔質グラファイト化フィルム、炭素繊維クロス、またはグラファイト繊維クロスである、複合炭素質基板の製造方法である。
（２）本発明の第二は、上記炭素繊維の平均直径が２０ｎｍ以下である（１）に記載の複合炭素質基板の製造方法である。
（３）本発明の第三は、上記金属触媒が遷移金属、またはその酸化物から選ばれた少なくとも一種類である、（１）または（２）に記載の複合炭素質基板の製造方法である。
（４）本発明の第四は、炭素質基板上への金属触媒の担持方法がスパッタリング法、真空蒸着法、イオンプレーティング法、ＥＢ蒸着法、または化学蒸着法から選ばれた少なくとも一つである、（１）〜（３）のいずれかに記載の複合炭素質基板の製造方法である。
（５）本発明の第五は、炭素質基板上への金属触媒の担持方法が平均粒径２０ｎｍ以下の超微粉末を分散した溶媒中への該炭素質基板の浸漬法である、（１）〜（３）のいずれかに記載の複合炭素質基板の製造方法である。
（６）上記多孔質グラファイト化フィルムが多孔質ポリイミドから得られる多孔質グラファイト化フィルムである、（１）〜（５）のいずれかに記載の複合炭素質基板の製造方法である。
（１’）本発明は、炭素質基板面に金属触媒を担持し、該炭素質基板を５００〜１２００℃の温度で加熱して炭素質基板上に炭素繊維を成長させる事を特徴とし、当該炭素質基板が多孔質炭素、多孔質グラファイト、炭素繊維クロス、またはグラファイト繊維クロスである、複合炭素質基板の製造方法である。
（２’）本発明は、上記炭素繊維の平均直径が２０ｎｍ以下である（１’）に記載の複合炭素質基板の製造方法である。
（３’）本発明は、上記金属触媒が遷移金属、またはその酸化物から選ばれた少なくとも一種類である、（１’）または（２’）に記載の複合炭素質基板の製造方法である。
（４’）本発明は、炭素質基板上への金属触媒の担持方法がスパッタリング法、真空蒸着法、イオンプレーティング法、ＥＢ蒸着法、または化学蒸着法から選ばれた少なくとも一つである、（１’）〜（３’）のいずれかに記載の複合炭素質基板の製造方法である。
（５’）本発明は、炭素質基板上への金属触媒の担持方法が平均粒径２０ｎｍ以下の超微粉末を分散した溶媒中への該炭素質基板の浸漬法である、（１’）〜（３’）のいずれかに記載の複合炭素質基板の製造方法である。
（６’）上記多孔質グラファイトが多孔質ポリイミドから得られる多孔質グラファイトである、（１’）〜（５’）のいずれかに記載の複合炭素質基板の製造方法である。
【００１５】
最初に本発明になる液相中でのＣＮＴの作製法についてのべる。
【００１６】
本発明ではＣＮＴを成長させる基板として炭素質材料が使用される。ここで、炭素質材料とは炭素が主成分である材料の事を言う。たとえば各種有機・高分子化合物を熱分解して得られる炭素・グラファイト材料、炭素繊維、グラファイト繊維、活性炭、ガラス状炭素、タールやピッチなどから得られる炭素・グラファイト材料、天然のグラファイトなどを言う。これらの炭素質材料と各種バインダ−高分子とからなる成型体、成型体をさらに熱処理して得られる炭素・グラファイト材料、などは好ましく使用できる。また、多孔質の有機フィルムや繊維状の織物、発泡によって得られる有機物、等を熱処理して得られる炭化物、グラファイト化物はいずれも本目的にとって特に好ましく用いられる。さらに、これらの炭素質材料と銅、鉄、ニッケル、ステンレスなどの金属との積層体、各種金属粉体との複合材料であっても良い。
例えば、芳香族ポリイミドフィルムを不活性ガス中、２４００℃以上に加熱して得られるグラファイトフィルムや多孔質ポリイミドから得られる多孔質グラファイト化フィルムは好ましく用いられる。また、各種炭素繊維クロス、グラファイト繊維クロスもまた好ましく用いられる。
本発明では上記の炭素質基板材料の表面に炭素繊維を成長させるための触媒が担持される。触媒としては遷移金属および遷移金属酸化物がもちいられる。具体的には、鉄、ニッケル、コバルト、タングステン、モリブデン，チタン、タンタルなどの金属およびその酸化物が好ましく用いられ、鉄、ニッケル、コバルトおよびその酸化物は特に好ましく用いられる。これらの金属触媒は微粉末である事が好ましく、平均粒径が５０ｎｍ以下、より好ましくは１０ｎｍ以下、最も好ましくは４ｎｍ以下である。
この様な粒径の金属触媒を炭素質材料の表面に担持する第一の方法は、スパッタリング法、真空蒸着法、イオンプレーティング法、ＥＢ蒸着法、または化学蒸着法などの手法を用いて金属触媒を担持する方法である。これらの方法で形成する場合に金属触媒は極めて微量で良く、全体として膜を形成するような量である必要はない。計算上金属触媒層は２〜１０ｎｍ程度の厚さで十分で、この様な薄膜の場合、金属触媒は膜を形成していると考えるよりは極めて微細な粒子として存在していると考えられる。
これらの粉体を担持する第二の方法は、まず、金属超微粉末を有機溶媒中に分散させて形成した溶液中に浸漬する方法である。より強固な担持を実現するために有機溶媒中に高分子接着剤を加えておいても良い。金属触媒の担持はディプの後に乾燥する事によって行う。乾燥後に炭素質基板を加熱し、高分子接着剤を炭素化しておいても良い。
また、炭素質基板上への金属触媒の担持方法として、鉄、コバルト、ニッケル、タングステンを含む有機金属化合物の有機溶媒中への浸積により行う事もできる。さらに、炭素質基板を作製する場合に最初から有機高分子材料やタールピッチなどの原料に上記金属触媒を添加しておき、しかる後に加熱による炭素化、グラファイト化を進めて金属触媒を含む電極を作製してもよい。
先に述べた様にＣＮＴの作製は通常気相中で行われアーク放電法、レーザーアブレーション法、ＣＶＤ法などが使用される。しかし、本発明のＣＮＴの作製は有機溶媒の中で行われる事にその最大の特徴があり、アルコール類、炭化水素系溶媒のみでなく広範囲な種類の有機液体が使用でき、これらの混合溶媒であっても構わない。具体的な例としてはメタノール、エタノール、プロパノール、ブタノール、アミルアルコール、ヘキサノール、シクロヘキサノール、ヘプタノール、オクチルアルコール、シクロヘキサン、ジエチルケトン、ｎ−ヘプタン、ｎ-ヘキサン、イソオクタン、ｎ−デカン、ベンゼン、トルエン、キシレン等が挙げられる。ＣＮＴ作製のための炭素源はこの有機溶媒の炭素であり、メタノール、エタノール、ブタノールなどは特に好ましく用いられる。
【００１７】
有機溶媒中での炭素繊維の作製には有機溶媒中で炭素基板を何らかの手法で６００℃から１２００℃の温度に加熱する。加熱には直流電流の印加による抵抗加熱、高周波誘導加熱、赤外線加熱、レーザー加熱などが用いられ、簡便な加熱という面から抵抗加熱が最も好ましく用いられる。この場合には炭素電極は電流印加によるジュール熱の発生によって加熱されるので、炭素電極自体が適当な抵抗値を持つ必要がある。基板の体積抵抗値はその基板の大きさによって異なるので一概には規定できないが、一般的に抵抗値として１０8Ω以下である事が望ましく、１０4Ω以下である事はより好ましい。
【００１８】
実際の反応ＣＮＴ成長反応は以下の様に行う。反応容器にアルコール（例えばブタノール）を満たし、金属触媒を担持した炭素基板にリード線を取り付けてアルコール溶媒中に固定する。反応容器内部を不活性ガスで満たし、反応器の周りを冷却水で冷却しておく。反応器の上部には揮発するアルコールを液化・還流する凝縮器をつけておく。この様にセッティングした炭素基板に直流電流を印加し、温度が６００℃〜１２００℃になるように昇温する。反応速度は温度によって異なるが、例えば８００℃であれば１分間程度で基板に垂直方向に長さ２μｍのＣＮＴが生成し、５分間の反応では約１０μｍの長さのＣＮＴが生成した。ＣＮＴの平均直径は担持触媒の種類、粒径、担持方法、によって異なるが、６〜１０ｎｍの直径のＣＮＴが得られる事が多く、基板上にびっしりとＣＮＴを成長させる事が出来る。
この液相反応の特徴の一つは炭素基板として多孔質基板を使用した場合、孔の中にもＣＮＴを生成させる事が出来るという点である。炭素基板を電池やコンデンサ用の電極として使用する場合その表面積を大きくする事が求められる。本発明の手法で多孔質炭素質基板の表面と内部にＣＮＴを形成した電極は表面積を極めて大きく出来るので、その様な観点から見て有用な方法である。一般的に気相法では多孔質材料の内部にＣＮＴを形成することは困難であるので、本発明の方法は極めて有用な手法である事がわかる。
【００１９】
【発明の実施の形態】
【００２０】
【実施例】
以下、実施例により本発明をより具体的に説明する。
【００２１】
（参考例１）
ポリイミドフィルム（鐘淵化学工業（株）製、ＡＨ（厚さ７５μｍ）をアルゴン中２７００℃で加熱してグラファイト化フィルム（厚さ３０μｍ）を得た。このフィルムの表面にマグネトロンスパッタリング法を用いて測定上５ｎｍの厚さになるようにＦｅおよびＦｅＯｘを蒸着した。次にこのフィルムを幅２０ｍｍ、長さ５０ｍｍになるように切断しグラファイト電極とした。
【００２２】
上記グラファイト基板に銅電極を取り付け、ｎ−ブタノ-ル溶媒で満たされた反応容器中にセッティングした。銅電極は厚さ２ｍｍの２枚の板で上記グラファイト基板の短面（幅２０ｍｍ部分）を挟む様になっている。反応容器をアルゴン置換した後、外部から銅電極を通して直流電流を印加してグラファイト基板を加熱した。加熱温度は８００℃とした。反応容器の回りは水冷され、反応器の上部には水冷凝縮器がとりつけられｎ−ブタノールが還流するようになっている。また、温度測定は赤外放射温度計で計測した。
【００２３】
５分間加熱後印加電流を切断し、試料を取り出した後乾燥し、電子顕微鏡でその表面を観察した。その結果長さ約１０μｍの極めて細い炭素繊維が基板表面にびっしりと成長していた。炭素繊維の直径は４ｎｍ〜１６ｎｍの間に分布しておりその平均の直径は８ｎｍであった。
（実施例２）
４,４’−ジアミノジフェニルエーテル（０．９９５モル）と３, ３’，４，４’−ビフェニルテトラカルボン酸（１．０モル）をＮＭＰ溶媒中で４０℃、６時間反応させてポリイミド前駆体溶液（前駆体濃度２０％）を合成した。得られたポリイミド前駆体溶液を厚みが１５０μｍになるように膜形成し、溶媒置換速度調整剤としてポリオレフィン製多孔質膜（宇部興産製、ＵＰ−３０２５）で表面を被覆した。この積層体をメタノール中に浸漬し、溶媒置換速度調整剤を介して溶媒置換を行うことでポリイミド前駆体の析出多孔質化を行った。析出したポリイミド多孔質フィルムを水中に１５分間浸漬した後、基板から剥離しピンテンターに固定した状態で大気中３００℃で１２分間熱処理を行い、イミド化を行った。得られた多孔質ポリイミドフィルムの厚さは４４μｍ、空孔率は６０％、平均孔径は０．７μｍで孔は貫通孔であった。次に、この様にして得られたポリイミド多孔質フィルムをアルゴンガス中２６００℃の温度で炭素化・グラファイト化し多孔質グラファイト基板フィルムを得た。
【００２４】
上記、多孔質グラファイト基板面に参考例１と同じ方法で金属触媒を担持し、しかる後に同じ手法で炭素繊維を成長させた。表面及びその電子顕微鏡観察で多孔質フィルムの表面および孔内部にびっしりとＣＮＴの成長した基板がえられた。この様にして作製された基板は非常に大きな表面積を有しており各種二次電池、二重層キャパシタなどのコンデンサの電極・集電材料として好ましく用いられる。
【００２５】
（参考例３）
５種類のＣ／Ｃコンポジット、東海カーボン製Ｃ−２０８０，Ｇ−２０８０、東北協和カーボンＭＦ３０６−３、ＭＦ３０１−２、東芝セラミックＣＰ１０１を用い、これらの基板に参考例１と同じ方法で金属Ｎｉ触媒を担持した。担持量は理屈上の厚さが５ｎｍとなる量である。次に実施例と同じ方法でｎ-ブタノールの代わりにメタノールを使用して基板表面に炭素繊維を成長させた。９００℃で５分間反応させた結果、Ｃ／Ｃコンポジット表面には長さ約８μｍ、平均直径６ｎｍのＣＮＴがびっしりと成長していた。この様な炭素基板は非常に大きな表面積を持ち、各種電極として使用する事が出来る。
（実施例４）
参考例１と同じ方法でＰＡＮ系炭素繊維クロス（東レ（株）製、トレカＣＯ６１４１）を用いてクロス上にＣＮＴを成長させた。加熱温度は８００℃で５分間加熱後印加電流を切断し、試料を取り出した後乾燥し、電子顕微鏡でその表面を観察した。その結果長さ約１０μｍの極めて細い炭素繊維がＰＡＮ系炭素繊維クロス上にびっしりと成長していた。炭素繊維の直径は４ｎｍ〜１６ｎｍの間に分布しておりその平均の直径は８ｎｍであった。
（参考例５）
参考例３とおなじＣ／Ｃコンポジットを用い、アルコール溶媒中に分散したコバルト酸か鉄の超微粉末と酸化鉄と同じ量添加されたエポキシ樹脂とからなる溶液にＣ／Ｃコンポジットを浸漬、乾燥、熱処理し金属触媒を担持した。
金属微粉末分散有機溶媒の作製法は以下の通りである。まず、トルエン中にカチオン性活性剤ジデシルメチルアンモニウムブロマイドを溶解する。次に塩化コバルト六水和物を加え攪拌する。その後水素化ナトリウムで塩化コバルトを還元しコロイド溶液となる。このコロイド溶液にエタノールと水を加え余分な界面活性剤を沈殿、分離し超微粒子を得た。得られたコバルト超微粒子の平均の粒径は４ｎｍであった。
こうして得られた分散溶液にＣ／Ｃコンポジット基板を浸漬した。浸漬時間は１時間、乾燥条件は１００℃、２時間乾燥、熱処理条件は２００℃、３０分とした。この様にして作製した金属担持Ｃ／Ｃコンポジット表面に参考例３と同じ方法でＣＮＴを成長させた。９００℃で５分間反応させた結果、Ｃ／Ｃコンポジット表面には長さ約１２μｍ、平均直径８ｎｍのＣＮＴがびっしりと成長していた。この様な炭素基板は非常に大きな表面積を持ち、各種電極として使用する事が出来る。
（実施例６）
実施例２で用いた多孔質炭素基板を参考例５で用いたコバルト超微粉末分散溶液に浸漬し、熱処理をおこなって金属担持基板を得た。この基板をもちいて実施例４と同じ方法でその表面にＣＮＴを成長させた。９００℃で５分間反応させた結果、Ｃ／Ｃコンポジット表面には長さ約１２μｍ、平均直径８ｎｍのＣＮＴがびっしりと成長していた。この様な炭素基板は非常に大きな表面積を持ち、各種電極として使用する事が出来る。
（実施例７）
実施例４でもちいたＰＡＮ系炭素繊維クロス（東レ（株）製、トレカＣＯ６１４１）を用いて、実施例４で用いたコバルト超微粉末分散溶液に浸漬し、熱処理をおこなって金属担持基板を得た。この基板を用いて参考例５と同じ方法でクロス上にＣＮＴを成長させた。電子顕微鏡でその表面を観察した。その結果長さ約１０μｍの極めて細い炭素繊維がＰＡＮ系炭素繊維クロス上にびっしりと成長していた。炭素繊維の平均直径は８ｎｍであった。
（参考例８）
参考例３とおなじＣ／Ｃコンポジットを用い有機金属溶液（（株）高純度化学研究所製Ｆｅ−０３）の希薄溶液にディップし、その後空気中で４００℃に加熱して、Ｃ／Ｃコンポジットの表面にＦｅ２Ｏ３の金属触媒を担持した。この基板を元に参考例１と同じ方法でその表面にＣＮＴを成長させた。その結果長さ約１０μｍの極めて細い炭素繊維が基板上にびっしりと成長していた。
【００２６】
【発明の効果】
本発明によれば、炭素質基板上にきわめて微細な炭素繊維を成長させる事が出来、その様な処理によって基板の表面積を非常に大きくできる。この様な手法で作製した炭素基板は各種電池の電極、各種コンデンサ電極等として広範囲な応用が可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a carbonaceous substrate used as various batteries such as lithium batteries, electrodes of various capacitors such as double layer capacitors, current collectors, and the like.
[0002]
[Prior art]
Carbon materials and graphite materials have an important position as industrial materials due to their excellent heat resistance, chemical resistance, high thermal conductivity, and high electrical conductivity. Electrical conductors, electrodes, current collectors, heat dissipation materials, heat-resistant sealing materials Widely used as gaskets, heating elements, etc.
In recent years, vapor-grown carbon fibers have attracted attention, and among them, vapor-grown carbon fibers called carbon nanotubes (CNT) have attracted much attention in recent years because of their excellent physical properties. Known methods for producing vapor-grown carbon fibers include arc discharge, laser ablation, and CVD, and many patents have been filed. Since CNT is a very fine carbon fiber, its handling is extremely difficult, and in order to make use of its excellent properties in the field of electronics, it has been necessary to make CNT easy to handle. However, since the vapor-grown carbon fiber is produced in a vacuum as the name suggests, it has been extremely difficult to grow CNTs in a certain direction only in necessary portions. In addition, since the production of CNTs in the gas phase always generates amorphous carbon as well as CNTs, it is difficult to remove them.
On the other hand, a method for producing CNTs on a silicon substrate in a liquid such as methanol or butanol has recently been published.
[0003]
[Patent Document 1]
JP 2002-69643 A
[0004]
[Patent Document 2]
JP 2002-180252 A
[0005]
[Patent Document 3]
JP2002-220214
[0006]
[Patent Document 4]
JP 2000-86217 A
[0007]
[Patent Document 5]
JP 06-325623 A
[0008]
[Patent Document 6]
JP 07-216660 A
[0009]
[Patent Document 7]
JP 08-231210
[0010]
[Patent Document 8]
JP 09-221309
[0011]
[Non-Patent Document 1]
Y. Zhang, et, al., Jpn. J. Appl. Phys. Vol. 41, L408 (2002)
[0012]
[Non-Patent Document 2]
Y. Zhang, et, al., J. Mater. Res., Vol. 17, 9, 2457 (2002)
[0013]
[Problems to be solved by the invention]
The present invention relates to a method for producing a composite carbonaceous substrate characterized in that carbonaceous fibers are grown in a liquid on the surface of a carbonaceous material. We have studied various methods for producing carbon fibers in a liquid, developed a new method for producing a composite carbon substrate for growing CNTs on the surface of a carbonaceous material, and achieved the present invention. The carbon electrode developed by this method has a very large surface area and is used for various batteries such as lithium batteries, electrodes for various capacitors such as double layer capacitors, current collectors, electrodes for FED (field emission display), or for gas adsorption. Can be used in a wide range of applications as a substrate.
[0014]
[Means for Solving the Problems]
(1) The first aspect of the present invention is characterized in that a metal catalyst is supported on the surface of a carbonaceous substrate, and the carbonaceous substrate is heated at a temperature of 500 to 1200 ° C. to grow carbon fibers on the carbonaceous substrate. , the carbonaceous substrate is a multi-porous graphitized film, a carbon fiber cloth or graphite fiber cloth, a method for manufacturing a composite carbonaceous substrate.
(2) A second aspect of the present invention is the method for producing a composite carbonaceous substrate according to (1), wherein the average diameter of the carbon fibers is 20 nm or less.
(3) A third aspect of the present invention is the method for producing a composite carbonaceous substrate according to (1) or (2), wherein the metal catalyst is at least one selected from transition metals or oxides thereof. .
(4) According to a fourth aspect of the present invention, the method for supporting the metal catalyst on the carbonaceous substrate is at least one selected from sputtering, vacuum deposition, ion plating, EB deposition, or chemical vapor deposition. A method for producing a composite carbonaceous substrate according to any one of (1) to (3).
(5) A fifth aspect of the present invention is a method for immersing the carbonaceous substrate in a solvent in which an ultrafine powder having an average particle size of 20 nm or less is dispersed as a method for supporting the metal catalyst on the carbonaceous substrate. The method for producing a composite carbonaceous substrate according to any one of (1) to (3).
(6) The method for producing a composite carbonaceous substrate according to any one of (1) to (5), wherein the porous graphitized film is a porous graphitized film obtained from porous polyimide.
(1 ′) The present invention is characterized in that a metal catalyst is supported on a carbonaceous substrate surface, the carbonaceous substrate is heated at a temperature of 500 to 1200 ° C., and carbon fibers are grown on the carbonaceous substrate. A method for producing a composite carbonaceous substrate, wherein the carbonaceous substrate is porous carbon, porous graphite, carbon fiber cloth, or graphite fiber cloth.
(2 ′) The present invention is the method for producing a composite carbonaceous substrate according to (1 ′), wherein the carbon fiber has an average diameter of 20 nm or less.
(3 ′) The present invention is the method for producing a composite carbonaceous substrate according to (1 ′) or (2 ′), wherein the metal catalyst is at least one selected from transition metals or oxides thereof. .
(4 ′) In the present invention, the method for supporting the metal catalyst on the carbonaceous substrate is at least one selected from a sputtering method, a vacuum deposition method, an ion plating method, an EB deposition method, or a chemical vapor deposition method. (1 ') It is a manufacturing method of the composite carbonaceous substrate in any one of (3').
(5 ′) The present invention is a method for immersing the carbonaceous substrate in a solvent in which an ultrafine powder having an average particle size of 20 nm or less is dispersed, wherein the method for supporting the metal catalyst on the carbonaceous substrate is (1 ′). It is a manufacturing method of the composite carbonaceous substrate in any one of-(3 ').
(6 ′) The method for producing a composite carbonaceous substrate according to any one of (1 ′) to (5 ′), wherein the porous graphite is porous graphite obtained from porous polyimide.
[0015]
First, a method for producing CNTs in a liquid phase according to the present invention will be described.
[0016]
In the present invention, a carbonaceous material is used as a substrate for growing CNTs. Here, the carbonaceous material refers to a material mainly composed of carbon. For example, carbon / graphite material obtained by pyrolyzing various organic / polymer compounds, carbon fiber, graphite fiber, activated carbon, glassy carbon, carbon / graphite material obtained from tar or pitch, natural graphite, etc. Molded bodies composed of these carbonaceous materials and various binder-polymers, carbon / graphite materials obtained by further heat-treating the molded bodies, and the like can be preferably used. In addition, a porous organic film, a fibrous woven fabric, an organic material obtained by foaming, a carbide obtained by heat treatment, and a graphitized material are all particularly preferably used for this purpose. Further, a laminate of these carbonaceous materials and a metal such as copper, iron, nickel, and stainless steel, or a composite material of various metal powders may be used.
For example, a graphite film obtained by heating an aromatic polyimide film in an inert gas to 2400 ° C. or higher, or a porous graphitized film obtained from porous polyimide is preferably used. Various carbon fiber cloths and graphite fiber cloths are also preferably used.
In the present invention, a catalyst for growing carbon fibers is supported on the surface of the carbonaceous substrate material. As the catalyst, transition metals and transition metal oxides are used. Specifically, metals such as iron, nickel, cobalt, tungsten, molybdenum, titanium, and tantalum and oxides thereof are preferably used, and iron, nickel, cobalt, and oxides thereof are particularly preferably used. These metal catalysts are preferably fine powders and have an average particle size of 50 nm or less, more preferably 10 nm or less, and most preferably 4 nm or less.
The first method for supporting a metal catalyst having such a particle size on the surface of a carbonaceous material is to use a technique such as sputtering, vacuum deposition, ion plating, EB deposition, or chemical vapor deposition. This is a method of supporting a catalyst. When formed by these methods, the amount of the metal catalyst may be extremely small, and it is not necessary to form such an amount as to form a film as a whole. In calculation, it is sufficient that the metal catalyst layer has a thickness of about 2 to 10 nm. In the case of such a thin film, it is considered that the metal catalyst exists as extremely fine particles rather than forming a film.
The second method for supporting these powders is a method in which metal ultrafine powder is first immersed in a solution formed by dispersing it in an organic solvent. In order to realize stronger support, a polymer adhesive may be added to the organic solvent. The metal catalyst is supported by drying after dipping. The carbonaceous substrate may be heated to carbonize the polymer adhesive after drying.
Further, as a method for supporting the metal catalyst on the carbonaceous substrate, it can be carried out by immersing an organometallic compound containing iron, cobalt, nickel, or tungsten in an organic solvent. Furthermore, when producing a carbonaceous substrate, the above metal catalyst is added to the raw materials such as organic polymer materials and tar pitch from the beginning, and then the carbon containing the catalyst is advanced by carbonization and graphitization by heating. It may be produced.
As described above, CNT is usually produced in a gas phase, and arc discharge method, laser ablation method, CVD method or the like is used. However, the production of the CNT of the present invention has the greatest feature that it is carried out in an organic solvent. A wide variety of organic liquids can be used in addition to alcohols and hydrocarbon solvents, and these mixed solvents can be used. It does not matter. Specific examples include methanol, ethanol, propanol, butanol, amyl alcohol, hexanol, cyclohexanol, heptanol, octyl alcohol, cyclohexane, diethyl ketone, n-heptane, n-hexane, isooctane, n-decane, benzene, toluene, And xylene. The carbon source for producing CNT is carbon of this organic solvent, and methanol, ethanol, butanol and the like are particularly preferably used.
[0017]
For the production of carbon fibers in an organic solvent, the carbon substrate is heated to a temperature of 600 ° C. to 1200 ° C. in some manner in the organic solvent. For heating, resistance heating by applying a direct current, high-frequency induction heating, infrared heating, laser heating, or the like is used, and resistance heating is most preferably used in terms of simple heating. In this case, since the carbon electrode is heated by the generation of Joule heat by applying current, the carbon electrode itself needs to have an appropriate resistance value. Since the volume resistance value of the substrate differs depending on the size of the substrate, it cannot be defined unconditionally. However, generally, the resistance value is preferably 10 8 Ω or less, and more preferably 10 4 Ω or less.
[0018]
The actual reaction CNT growth reaction is performed as follows. A reaction vessel is filled with alcohol (for example, butanol), and a lead wire is attached to a carbon substrate carrying a metal catalyst and fixed in an alcohol solvent. The inside of the reaction vessel is filled with an inert gas, and the periphery of the reactor is cooled with cooling water. A condenser for liquefying and refluxing volatile alcohol is attached to the top of the reactor. A direct current is applied to the carbon substrate set in this way, and the temperature is raised so that the temperature becomes 600 ° C to 1200 ° C. Although the reaction rate varies depending on the temperature, for example, when the temperature is 800 ° C., CNTs having a length of 2 μm are generated in a direction perpendicular to the substrate in about 1 minute, and CNTs having a length of about 10 μm are generated by the reaction for 5 minutes. Although the average diameter of CNT varies depending on the type of supported catalyst, particle size, and supporting method, CNTs having a diameter of 6 to 10 nm are often obtained, and CNTs can be grown tightly on the substrate.
One of the features of this liquid phase reaction is that when a porous substrate is used as the carbon substrate, CNTs can also be generated in the pores. When a carbon substrate is used as an electrode for a battery or a capacitor, it is required to increase its surface area. Since an electrode having CNTs formed on the surface and inside of a porous carbonaceous substrate by the method of the present invention can have a very large surface area, it is a useful method from such a viewpoint. In general, it is difficult to form CNT inside a porous material by a gas phase method, and thus it can be seen that the method of the present invention is a very useful method.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
[0020]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0021]
(Reference Example 1)
A polyimide film (manufactured by Kaneka Chemical Industry Co., Ltd., AH (thickness: 75 μm)) was heated in argon at 2700 ° C. to obtain a graphitized film (thickness: 30 μm). For the measurement, Fe and FeOx were deposited so as to have a thickness of 5 nm, and then this film was cut to have a width of 20 mm and a length of 50 mm to obtain a graphite electrode.
[0022]
A copper electrode was attached to the graphite substrate and set in a reaction vessel filled with n-butanol solvent. The copper electrode sandwiches the short surface (width 20 mm portion) of the graphite substrate between two 2 mm thick plates. After the reaction vessel was purged with argon, a direct current was applied from the outside through a copper electrode to heat the graphite substrate. The heating temperature was 800 ° C. The reaction vessel is cooled with water, and a water-cooled condenser is attached to the upper part of the reactor so that n-butanol is refluxed. The temperature was measured with an infrared radiation thermometer.
[0023]
After heating for 5 minutes, the applied current was cut, the sample was taken out and dried, and the surface was observed with an electron microscope. As a result, extremely thin carbon fibers having a length of about 10 μm were grown on the substrate surface. The diameter of the carbon fiber was distributed between 4 nm and 16 nm, and the average diameter was 8 nm.
(Example 2)
Polyimide precursor by reacting 4,4′-diaminodiphenyl ether (0.995 mol) and 3,3 ′, 4,4′-biphenyltetracarboxylic acid (1.0 mol) in NMP solvent at 40 ° C. for 6 hours. A solution (precursor concentration 20%) was synthesized. A film was formed so that the obtained polyimide precursor solution had a thickness of 150 μm, and the surface was covered with a porous film made of polyolefin (manufactured by Ube Industries, UP-3025) as a solvent replacement rate adjusting agent. This laminated body was immersed in methanol, and solvent substitution was performed via a solvent substitution rate adjusting agent, whereby the porous precipitation of the polyimide precursor was performed. The deposited polyimide porous film was immersed in water for 15 minutes, and then heat-treated at 300 ° C. for 12 minutes in the atmosphere while being peeled off from the substrate and fixed on a pin tenter to perform imidization. The resulting porous polyimide film had a thickness of 44 μm, a porosity of 60%, an average pore diameter of 0.7 μm, and the holes were through-holes. Next, the polyimide porous film thus obtained was carbonized and graphitized in an argon gas at a temperature of 2600 ° C. to obtain a porous graphite substrate film.
[0024]
The metal catalyst was supported on the porous graphite substrate surface by the same method as in Reference Example 1, and then carbon fibers were grown by the same method. By observing the surface and the electron microscope, a substrate on which the CNTs grew closely on the surface of the porous film and inside the pores was obtained. The substrate thus produced has a very large surface area and is preferably used as an electrode / collecting material for capacitors such as various secondary batteries and double layer capacitors.
[0025]
(Reference Example 3)
Five types of C / C composites, Tokai Carbon C-2080, G-2080, Tohoku Kyowa Carbon MF306-3, MF301-2, and Toshiba Ceramic CP101 were used. Was supported. The supported amount is such that the theoretical thickness is 5 nm. Next, carbon fibers were grown on the substrate surface by using methanol in place of n-butanol in the same manner as in the examples. As a result of reacting at 900 ° C. for 5 minutes, CNTs having a length of about 8 μm and an average diameter of 6 nm grew tightly on the C / C composite surface. Such a carbon substrate has a very large surface area and can be used as various electrodes.
(Example 4)
CNTs were grown on the cloth using a PAN-based carbon fiber cloth (Torayca CO6141 manufactured by Toray Industries, Inc.) in the same manner as in Reference Example 1. After heating at 800 ° C. for 5 minutes, the applied current was cut, the sample was taken out and dried, and the surface was observed with an electron microscope. As a result, extremely thin carbon fibers having a length of about 10 μm were grown tightly on the PAN-based carbon fiber cloth. The diameter of the carbon fiber was distributed between 4 nm and 16 nm, and the average diameter was 8 nm.
(Reference Example 5)
Using the same C / C composite as in Reference Example 3, the C / C composite was immersed in a solution composed of an ultrafine powder of cobalt acid or iron dispersed in an alcohol solvent and an epoxy resin added in the same amount as iron oxide, and dried. The metal catalyst was supported by heat treatment.
The method for preparing the metal fine powder-dispersed organic solvent is as follows. First, the cationic activator didecylmethylammonium bromide is dissolved in toluene. Next, cobalt chloride hexahydrate is added and stirred. Thereafter, the cobalt chloride is reduced with sodium hydride to form a colloidal solution. Ethanol and water were added to this colloidal solution to precipitate and separate excess surfactant to obtain ultrafine particles. The average particle diameter of the obtained cobalt ultrafine particles was 4 nm.
The C / C composite substrate was immersed in the dispersion solution thus obtained. Immersion time was 1 hour, drying conditions were 100 ° C., drying for 2 hours, and heat treatment conditions were 200 ° C. and 30 minutes. CNTs were grown on the surface of the metal-supported C / C composite produced in this manner by the same method as in Reference Example 3. As a result of reacting at 900 ° C. for 5 minutes, CNTs having a length of about 12 μm and an average diameter of 8 nm grew tightly on the C / C composite surface. Such a carbon substrate has a very large surface area and can be used as various electrodes.
(Example 6)
The porous carbon substrate used in Example 2 was immersed in the ultrafine cobalt powder dispersion solution used in Reference Example 5, and heat treatment was performed to obtain a metal-carrying substrate. Using this substrate, CNTs were grown on the surface in the same manner as in Example 4. As a result of reacting at 900 ° C. for 5 minutes, CNTs having a length of about 12 μm and an average diameter of 8 nm grew tightly on the C / C composite surface. Such a carbon substrate has a very large surface area and can be used as various electrodes.
(Example 7)
Using a PAN-based carbon fiber cloth (Toray Industries Co., Ltd., Torayca CO6141) used in Example 4, it was immersed in the cobalt ultrafine powder dispersion used in Example 4 and subjected to heat treatment to obtain a metal-supported substrate. It was. Using this substrate, CNTs were grown on the cloth in the same manner as in Reference Example 5. The surface was observed with an electron microscope. As a result, extremely thin carbon fibers having a length of about 10 μm were grown tightly on the PAN-based carbon fiber cloth. The average diameter of the carbon fibers was 8 nm.
(Reference Example 8)
The same C / C composite as in Reference Example 3 was used to dip into a dilute solution of an organometallic solution (Fe-03, manufactured by Kojundo Chemical Laboratory Co., Ltd.), and then heated to 400 ° C. in the air. A Fe2O3 metal catalyst was supported on the surface of the substrate. Based on this substrate, CNTs were grown on the surface in the same manner as in Reference Example 1. As a result, extremely thin carbon fibers having a length of about 10 μm were grown on the substrate.
[0026]
【The invention's effect】
According to the present invention, extremely fine carbon fibers can be grown on a carbonaceous substrate, and the surface area of the substrate can be greatly increased by such treatment. The carbon substrate produced by such a method can be used in a wide range of applications as various battery electrodes, various capacitor electrodes, and the like.
Claims (6)
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2006219362A (en) * | 2005-02-08 | 2006-08-24 | Microphase Co Ltd | Synthetic method of carbon nanotube film by introduction of gas phase into liquid phase and synthesizing unit |
| US7917966B2 (en) | 2008-08-21 | 2011-03-29 | Snu R&Db Foundation | Aligned nanostructures on a tip |
| US8070929B2 (en) | 2008-08-21 | 2011-12-06 | Snu R&Db Foundation | Catalyst particles on a tip |
| JP5577089B2 (en) * | 2009-12-25 | 2014-08-20 | 日東電工株式会社 | Carbon nanotube composite structure and adhesive member |
| CN111933898B (en) * | 2020-06-12 | 2022-06-10 | 湖州凯金新能源科技有限公司 | High-performance graphite negative electrode material for lithium ion battery, and preparation method and application thereof |
| CN114284076B (en) * | 2021-12-31 | 2023-12-01 | 合肥工业大学 | Method for rapidly preparing high-activity carbon fiber supercapacitor electrode at high temperature based on Joule heat |
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