JP2018104269A - Production method of reduced graphene oxide - Google Patents
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Abstract
【課題】高導電性と高分散性を兼ね備えた還元グラフェンを作製する。【解決手段】酸化グラフェンを還元剤により還元する還元グラフェンの製造方法であって、酸化グラフェン分散液と、酸化グラフェンを還元しうる還元剤を含有する還元剤液とをそれぞれ別の流路から送液し、合流点における圧力が０．３ＭＰａ以上５００ＭＰａ以下となるよう合流させる工程を有する還元グラフェンの製造方法。【選択図】なしPROBLEM TO BE SOLVED: To produce reduced graphene having both high conductivity and high dispersibility. A method for producing reduced graphene by reducing graphene oxide with a reducing agent, wherein a graphene oxide dispersion liquid and a reducing agent liquid containing a reducing agent capable of reducing graphene oxide are sent from different channels. A method for producing reduced graphene, which comprises a step of liquefying and merging so that the pressure at a merging point becomes 0.3 MPa or more and 500 MPa or less. [Selection diagram] None
Description
本発明は、酸化グラフェンを還元して得られる還元グラフェンの製造方法に関する。 The present invention relates to a method for producing reduced graphene obtained by reducing graphene oxide.
グラフェンは炭素原子からなる二次元結晶であり、２００４年に発見されて以来非常に注目されている素材である。グラフェンは優れた電気、熱、光学、及び機械特性を有し、電池材料、エネルギー貯蔵材料、電子デバイス，複合材料などの領域で幅広い応用が期待されている。 Graphene is a two-dimensional crystal composed of carbon atoms and is a material that has received much attention since it was discovered in 2004. Graphene has excellent electrical, thermal, optical, and mechanical properties, and is expected to be widely applied in areas such as battery materials, energy storage materials, electronic devices, and composite materials.
このようなグラフェンの応用を実現するためには、低コスト化のための作製法の効率化、及び分散性の改善が必須の課題となる。 In order to realize the application of such graphene, it is essential to improve the efficiency of the manufacturing method for reducing the cost and improve the dispersibility.
グラフェンの製造法としては、機械剥離法、ＣＶＤ（Ｃｈｅｍｉｃａｌ Ｖａｐｏｒ Ｄｅｐｏｓｉｔｉｏｎ）法、ＣＥＧ（Ｃｒｙｓｔａｌ Ｅｐｉｔａｘｉａｌ Ｇｒｏｗｔｈ）法などが挙げられるが、これらの手法は生産性が低く、大量生産には適さない。これに対し、酸化還元法（天然黒鉛の酸化処理で酸化黒鉛または酸化グラフェンを得た後、還元反応によりグラフェンを作製する方法）はグラフェンの大量合成が可能であり、グラフェンを実用化するのに非常に重要な手法である。 Examples of the method for producing graphene include a mechanical peeling method, a CVD (Chemical Vapor Deposition) method, and a CEG (Crystal Epitaxy Growth) method, but these methods are low in productivity and are not suitable for mass production. On the other hand, the oxidation-reduction method (a method of producing graphene by a reduction reaction after obtaining graphite oxide or graphene oxide by oxidation treatment of natural graphite) enables mass synthesis of graphene, which is useful for putting graphene into practical use. This is a very important technique.
このようにして得られたグラフェンは、高い導電性能を持つ上に、薄片状の構造を持つため導電パスを多くすることができ、特に電池用の導電材料として高いポテンシャルを持つ。しかし、グラフェンはナノカーボンであるため凝集しやすく、単に酸化還元法でグラフェンを作製しても適度に分散することができずポテンシャルを発揮することができていなかった。 The graphene obtained in this manner has a high conductive performance and also has a flake-like structure, so that the number of conductive paths can be increased. In particular, it has a high potential as a conductive material for a battery. However, since graphene is a nanocarbon, it easily aggregates, and even if graphene is simply produced by the oxidation-reduction method, it cannot be appropriately dispersed and cannot exert its potential.
そこで、特許文献１では酸化黒鉛を加熱により膨張剥離させることで比表面積の高い薄片型の黒鉛を作製している。特許文献２では酸化グラフェンとリチウムイオン電池用電極活物質を混合した後に加熱することにより還元し、導電剤として活用している。特許文献３ではカテコールの存在下、グラフェンを還元することにより分散性の高いグラフェンを作製している。特許文献４ではグラフェンを二酸化炭素中で加圧して超臨界流体処理を行う手法が開示されている。 Therefore, in Patent Document 1, flaky graphite having a high specific surface area is produced by expanding and peeling graphite oxide by heating. In patent document 2, it reduces by heating after mixing a graphene oxide and the electrode active material for lithium ion batteries, and is utilizing as a electrically conductive agent. In Patent Document 3, graphene having high dispersibility is produced by reducing graphene in the presence of catechol. Patent Document 4 discloses a technique for performing supercritical fluid processing by pressurizing graphene in carbon dioxide.
特許文献１のように、加熱膨張により作製したグラフェンは高い比表面積が得られるが、高温加熱により溶媒が揮発した状態で作製するため、溶剤中への分散が困難になる。また、加熱還元では十分な導電性を得ることができない。 Although the graphene produced by thermal expansion as in Patent Document 1 has a high specific surface area, it is produced in a state where the solvent is volatilized by heating at a high temperature, so that dispersion in the solvent becomes difficult. Moreover, sufficient electroconductivity cannot be obtained by heat reduction.
特許文献２のように酸化グラフェンを他の粒子と混ぜて加熱する手法においても、特許文献１の場合と同様、加熱処理によりグラフェンを得ているため十分な導電性が得られない。また、粒子と混合する用途に適用が限定される。 Even in the method of mixing graphene oxide with other particles and heating as in Patent Document 2, as in Patent Document 1, sufficient conductivity cannot be obtained because graphene is obtained by heat treatment. Moreover, application is limited to the use which mixes with particle | grains.
また、特許文献３のように表面処理剤を使用すると、分散性は良くなるものの、表面処理剤の影響で抵抗が低下する課題があった。 Moreover, when a surface treatment agent is used like patent document 3, although the dispersibility became good, there existed a subject that resistance fell under the influence of a surface treatment agent.
特許文献４ではグラフェンを超臨界流体中で処理しているものの、グラフェンを剥離させるのに十分な力を与えることができず、剥離度に問題があり、分散性が不十分であった。 In Patent Document 4, although graphene is processed in a supercritical fluid, a sufficient force cannot be applied to exfoliate graphene, there is a problem in exfoliation degree, and dispersibility is insufficient.
本発明は、高導電性と高分散性を兼ね備えたグラフェンを作製することを課題とする。 An object of the present invention is to produce graphene having both high conductivity and high dispersibility.
本発明者らは鋭意検討した結果、高せん断力をかけながら、酸化グラフェンを還元する手法により、高導電性と高分散性を兼ね備えた還元グラフェンを作製できることを見出した。すなわち、本発明は、酸化グラフェンを還元剤により還元する還元グラフェンの製造方法であって、酸化グラフェン分散液と、酸化グラフェンを還元しうる還元剤を含有する還元剤液とをそれぞれ別の流路から送液し、合流点における圧力が０．３ＭＰａ以上５００ＭＰａ以下となるよう合流させる工程を有する還元グラフェンの製造方法である。 As a result of intensive studies, the present inventors have found that reduced graphene having both high conductivity and high dispersibility can be produced by a technique of reducing graphene oxide while applying a high shearing force. That is, the present invention is a method for producing reduced graphene in which graphene oxide is reduced with a reducing agent, wherein the graphene oxide dispersion liquid and the reducing agent liquid containing a reducing agent capable of reducing graphene oxide are provided in different flow paths. The reduced graphene production method has a step of feeding the solution so that the pressure at the joining point is 0.3 MPa or more and 500 MPa or less.
本発明の還元グラフェンの製造方法は、酸化グラフェン分散液と還元剤液とを、高いせん断力をかけながら混合することにより、グラフェンの剥離状態を維持しながら還元することが可能である。この手法により、高導電性と高分散性を兼ね備えた還元グラフェンを作製することが可能である。このようにして作製した還元グラフェンは、リチウムイオン電池用電極に適用することで優れた放電特性が得られる。また、樹脂と混合することにより高い導電性をもつ樹脂を得られる。 In the method for producing reduced graphene of the present invention, the graphene oxide dispersion liquid and the reducing agent liquid can be mixed while applying a high shearing force to reduce the graphene while maintaining the exfoliated state of the graphene. By this technique, reduced graphene having both high conductivity and high dispersibility can be produced. The reduced graphene produced in this way can provide excellent discharge characteristics when applied to an electrode for a lithium ion battery. Moreover, resin with high electroconductivity can be obtained by mixing with resin.
グラフェンとは、狭義には１原子の厚さのｓｐ２結合炭素原子のシート（単層グラフェン）を指すが、本明細書においては、単層グラフェンが積層した薄片状の形態を持つものも含めてグラフェンと呼ぶ。酸化グラフェンも同様に、積層した薄片状の形態を持つものも含めた呼称とする。 Graphene refers to a sheet (single-layer graphene) of sp 2 -bonded carbon atoms having a thickness of 1 atom in a narrow sense. However, in this specification, a sheet having a flaky shape in which single-layer graphene is stacked is included. Called graphene. Similarly, graphene oxide is also referred to as having a laminated flake shape.
また、本明細書において、「還元グラフェン」とは酸化グラフェンを還元して得られるグラフェンであって、還元処理前に対して、Ｘ線光電子分光分析（ＸＰＳ）によって測定された酸素原子の炭素原子に対する元素割合（酸化度）が低下しているもの全般を意味する相対的な概念である。典型的には、酸化度が０．４を超えるものが酸化グラフェン、０．４以下のものが還元グラフェンと呼称されるが、本発明においては特に限定されるものではない。また、酸化グラフェンと還元グラフェンを総称して単に「グラフェン」という場合がある。 In this specification, “reduced graphene” is graphene obtained by reducing graphene oxide, and is a carbon atom of an oxygen atom measured by X-ray photoelectron spectroscopy (XPS) before reduction treatment. It is a relative concept which means the whole thing in which the element ratio (oxidation degree) with respect to is decreasing. Typically, those having an oxidation degree exceeding 0.4 are referred to as graphene oxide, and those having a degree of oxidation of 0.4 or less are referred to as reduced graphene. However, the present invention is not particularly limited. In addition, graphene oxide and reduced graphene may be collectively referred to simply as “graphene”.
［酸化グラフェン分散液］
酸化グラフェンの作製法に特に限定は無く、ハマーズ法等の公知の方法を使用できる。また市販の酸化グラフェンを購入してもよい。酸化グラフェンの作製方法として、ハマーズ法を用いる場合を以下に例示する。
[Graphene oxide dispersion]
There is no particular limitation on the method for producing graphene oxide, and a known method such as a Hammers method can be used. Commercially available graphene oxide may be purchased. An example of using a Hammers method as a method for manufacturing graphene oxide is described below.
黒鉛（石墨粉）と硝酸ナトリウムを濃硫酸中に入れて攪拌しながら、過マンガン酸カリウムを温度が上がらないように徐々に添加し、２５〜５０℃下、０．２〜５時間攪拌反応する。その後イオン交換水を加えて希釈して懸濁液とし、８０〜１００℃で５〜５０分間反応する。最後に過酸化水素と脱イオン水を加え１〜３０分間反応して、酸化グラフェン分散液を得る。得られた酸化グラフェン分散液を濾過、洗浄し、酸化グラフェン水分散ゲルを得る。この酸化グラフェン水分散ゲルを希釈して酸化グラフェン水分散液が得られる。酸化グラフェン水分散液を得る際、酸化グラフェンを乾燥させる工程を経ないことが好ましい。 While adding graphite (graphite powder) and sodium nitrate in concentrated sulfuric acid and stirring, gradually add potassium permanganate so that the temperature does not rise and react at 25 to 50 ° C. for 0.2 to 5 hours with stirring. . Thereafter, ion-exchanged water is added for dilution to form a suspension, which is reacted at 80 to 100 ° C. for 5 to 50 minutes. Finally, hydrogen peroxide and deionized water are added and reacted for 1 to 30 minutes to obtain a graphene oxide dispersion. The obtained graphene oxide dispersion is filtered and washed to obtain a graphene oxide aqueous dispersion gel. This graphene oxide aqueous dispersion gel is diluted to obtain a graphene oxide aqueous dispersion. When obtaining the graphene oxide aqueous dispersion, it is preferable not to go through a step of drying the graphene oxide.
酸化グラフェンの原料となる黒鉛は、人造黒鉛・天然黒鉛のどちらでも良いが、天然黒鉛が好ましく用いられる。原料とする黒鉛のメッシュ数は２００００以下が好ましく、５０００以下がさらに好ましい。 The graphite used as the raw material for graphene oxide may be either artificial graphite or natural graphite, but natural graphite is preferably used. The number of meshes of graphite used as a raw material is preferably 20000 or less, and more preferably 5000 or less.
各反応物の割合は、一例として、黒鉛１０ｇに対し、濃硫酸を１５０〜３００ｍｌ、硝酸ナトリウムを２〜８ｇ、過マンガン酸カリウムを１０〜４０ｇ、過酸化水素を４０〜８０ｇである。硝酸ナトリウムと過マンガン酸カリウムを加える時は、氷浴を利用して温度を制御する。過酸化水素と脱イオン水を加える時、脱イオン水の質量は過酸化水素質量の１０〜２０倍である。濃硫酸は、質量含有量が７０％以上のものを利用することが好ましく、９７％以上のものを利用することがさらに好ましい。 As an example, the ratio of each reactant is 150 to 300 ml of concentrated sulfuric acid, 2 to 8 g of sodium nitrate, 10 to 40 g of potassium permanganate, and 40 to 80 g of hydrogen peroxide with respect to 10 g of graphite. When adding sodium nitrate and potassium permanganate, use an ice bath to control the temperature. When adding hydrogen peroxide and deionized water, the mass of deionized water is 10 to 20 times the mass of hydrogen peroxide. Concentrated sulfuric acid preferably has a mass content of 70% or more, more preferably 97% or more.
酸化グラフェンは高い分散性を有するが、酸化グラフェン自体は絶縁性で導電剤等に用いることはできない。酸化グラフェンの酸化度が高すぎると、還元して得られるグラフェン粉末の導電性が悪くなる場合があるため、酸化グラフェンにおけるＸ線光電子分光法によって測定される酸素原子に対する炭素原子の割合は０．５以下であることが好ましい。酸化グラフェンをＸ線光電子分光法測定する際には充分溶剤を乾燥させた状態で行う。 Although graphene oxide has high dispersibility, graphene oxide itself is insulative and cannot be used as a conductive agent. When the degree of oxidation of graphene oxide is too high, the conductivity of the graphene powder obtained by reduction may deteriorate. Therefore, the ratio of carbon atoms to oxygen atoms measured by X-ray photoelectron spectroscopy in graphene oxide is 0. 5 or less is preferable. When graphene oxide is measured by X-ray photoelectron spectroscopy, it is performed in a state where the solvent is sufficiently dried.
また、内部まで黒鉛が酸化されていないと還元したときに薄片状のグラフェン粉末が得られにくい。そのため、酸化グラフェンは、乾燥した酸化グラフェン粉末のエックス線回折測定をしたときにグラファイト構造特有のピークが検出されないことが望ましい。 Further, when the graphite is not oxidized to the inside, it is difficult to obtain a flaky graphene powder when reduced. Therefore, it is desirable that the graphene oxide does not detect a peak specific to the graphite structure when X-ray diffraction measurement is performed on the dried graphene oxide powder.
酸化グラフェンの酸化度は、黒鉛の酸化反応に用いる酸化剤の量を変化させることで調整することができる。具体的には、酸化反応の際に用いる、黒鉛に対する硝酸ナトリウム及び過マンガン酸カリウムの量が多いほど高い酸化度になり、少ないほど低い酸化度になる。黒鉛に対する硝酸ナトリウムの重量比は特に限定されるものではないが、０．２０以上０．８０以下であることが好ましく、０．２５以上０．５０以下であることがさらに好ましく、０．２７５以上０．４２５以下であることが特に好ましい。黒鉛に対する過マンガン酸カリウムの比は特に限定されるものではないが、１．０以上であることが好ましく、１．４以上であることがさらに好ましく、１．６５以上であることが特に好ましい。また、同様に４．０以下であることが好ましく、３．０以下であることがさらに好ましく、２．５５以下であることが特に好ましい。 The degree of oxidation of graphene oxide can be adjusted by changing the amount of oxidizing agent used for the oxidation reaction of graphite. Specifically, the higher the amount of sodium nitrate and potassium permanganate used in the oxidation reaction, the higher the degree of oxidation, and the lower the amount, the lower the degree of oxidation. The weight ratio of sodium nitrate to graphite is not particularly limited, but is preferably 0.20 or more and 0.80 or less, more preferably 0.25 or more and 0.50 or less, and 0.275 or more. It is especially preferable that it is 0.425 or less. The ratio of potassium permanganate to graphite is not particularly limited, but is preferably 1.0 or more, more preferably 1.4 or more, and particularly preferably 1.65 or more. Similarly, it is preferably 4.0 or less, more preferably 3.0 or less, and particularly preferably 2.55 or less.
酸化グラフェンは上記の例で示した手法では水分散液として作製される。水分散液から他の溶媒に置換する手法としては、水分散液に水以外の溶媒を加えて攪拌した後に、ろ過又は遠心分離機により濃縮する工程を繰り返すことで溶媒を置換することができる。 Graphene oxide is produced as an aqueous dispersion by the method shown in the above example. As a method for replacing the aqueous dispersion with another solvent, the solvent can be replaced by adding a solvent other than water to the aqueous dispersion and stirring, and then repeating a step of concentration by filtration or a centrifuge.
酸化グラフェン分散液の溶媒は水を含むことが好ましいが、酸化グラフェンが十分分散できる溶媒であれば他の溶媒であっても良く、混合溶媒であっても良い。複数の溶媒を使用する場合には相分離せずに相溶する溶媒であることが好ましい。酸化グラフェンを十分分散できる溶媒としては、Ｎ−メチルピロリドン、γ−ブチロラクトン、ジメチルアセトアミド、ジメチルスルホキシドなどが挙げられる。酸化グラフェン分散液の溶媒は、混合する還元剤液と相溶するものを用いることが好ましく、同一の溶媒であることが更に好ましい。還元剤液として水溶液を用いる場合には酸化グラフェン分散液は水分散液を用いることが好ましい。 The solvent of the graphene oxide dispersion preferably contains water, but may be another solvent or a mixed solvent as long as the graphene oxide can be sufficiently dispersed. In the case of using a plurality of solvents, a solvent that is compatible without phase separation is preferred. Examples of the solvent that can sufficiently disperse graphene oxide include N-methylpyrrolidone, γ-butyrolactone, dimethylacetamide, dimethylsulfoxide, and the like. As the solvent for the graphene oxide dispersion, it is preferable to use a solvent compatible with the reducing agent solution to be mixed, and it is more preferable that the solvent is the same. When an aqueous solution is used as the reducing agent solution, it is preferable to use an aqueous dispersion as the graphene oxide dispersion.
［還元剤液］
酸化グラフェンを還元しうる還元剤を含有する還元剤液は、還元剤が溶媒に溶けた還元剤液であってもよいし、還元剤自体が液体であるものであっても良い。還元剤としては、有機還元剤、無機還元剤が挙げられるが、還元後の洗浄の容易さから無機還元剤が好ましい。
[Reducing agent solution]
The reducing agent solution containing a reducing agent capable of reducing graphene oxide may be a reducing agent solution in which the reducing agent is dissolved in a solvent, or the reducing agent itself may be a liquid. Examples of the reducing agent include an organic reducing agent and an inorganic reducing agent, but an inorganic reducing agent is preferable because of easy cleaning after reduction.
有機還元剤としてはアルデヒド系還元剤、ヒドラジン誘導体還元剤、アルコール系還元剤が挙げられ、中でもアルコール系還元剤は比較的穏やかに還元することができるため、特に好適である。アルコール系還元剤としては、メタノール、エタノール、プロパノール、イソプロピルアルコール、ブタノール、ベンジルアルコール、フェノール、エタノールアミン、エチレングリコール、プロピレングリコール、ジエチレングリコール、などが挙げられる。中でも比較的沸点が高いブタノール、ベンジルアルコール、エタノールアミン、エチレングリコール、プロピレングリコール、ジエチレングリコールが好ましい。 Examples of the organic reducing agent include aldehyde-based reducing agents, hydrazine derivative reducing agents, and alcohol-based reducing agents. Among them, alcohol-based reducing agents are particularly suitable because they can be reduced relatively gently. Examples of the alcohol-based reducing agent include methanol, ethanol, propanol, isopropyl alcohol, butanol, benzyl alcohol, phenol, ethanolamine, ethylene glycol, propylene glycol, diethylene glycol, and the like. Of these, butanol, benzyl alcohol, ethanolamine, ethylene glycol, propylene glycol and diethylene glycol having a relatively high boiling point are preferred.
無機還元剤としては亜ジチオン酸ナトリウム、亜ジチオン酸カリウム、亜リン酸、水素化ホウ素ナトリウム、ヒドラジンなどが挙げられる。無機還元剤は、溶媒に溶解して還元剤液として用いられるが、無機還元剤の還元力が発現しやすい点で、水溶液とすることが好ましい。 Examples of the inorganic reducing agent include sodium dithionite, potassium dithionite, phosphorous acid, sodium borohydride, hydrazine and the like. The inorganic reducing agent is dissolved in a solvent and used as a reducing agent liquid. However, an aqueous solution is preferable because the reducing power of the inorganic reducing agent is easily exhibited.
還元剤としては、酸化グラフェンの還元が急速に行える還元力をもつものが好ましく、この観点から、亜ジチオン酸ナトリウム、亜ジチオン酸カリウム、水素化ホウ素ナトリウム、ヒドラジンが好ましく、亜ジチオン酸ナトリウム、亜ジチオン酸カリウムが特に好ましい。また、これらを水溶液として還元剤液とすることが特に好ましい。 As the reducing agent, those having a reducing power capable of rapidly reducing graphene oxide are preferable. From this viewpoint, sodium dithionite, potassium dithionite, sodium borohydride, and hydrazine are preferable, sodium dithionite, Potassium dithionate is particularly preferred. Further, it is particularly preferable to use these as an aqueous solution as a reducing agent solution.
酸化グラフェン分散液と還元剤液の組み合わせとしては、酸化グラフェンの水分散液と上記の無機還元剤の水溶液との組み合わせが最も好ましい。 As a combination of the graphene oxide dispersion and the reducing agent liquid, a combination of an aqueous dispersion of graphene oxide and an aqueous solution of the above inorganic reducing agent is most preferable.
［合流させる工程］
本発明の還元グラフェンの製造方法は、上記の酸化グラフェン分散液と還元剤液とをそれぞれ別の流路から送液し、合流点における圧力が０．３ＭＰａ以上５００ＭＰａ以下となるよう合流させる工程を有する。この工程により、酸化グラフェンと還元剤とが混合され、酸化グラフェンが還元される。
[Merge process]
The method for producing reduced graphene of the present invention includes a step of feeding the graphene oxide dispersion and the reducing agent solution from different flow paths, and joining them so that the pressure at the joining point is 0.3 MPa or more and 500 MPa or less. Have. Through this step, graphene oxide and a reducing agent are mixed and graphene oxide is reduced.
合流時に十分なせん断力を与えるために高圧で合流させる必要がある一方、圧力が高すぎると液体中の圧力差が生じるキャビテーション効果により気泡が発生するため、合流時の圧力は０．３ＭＰａ以上５００ＭＰａ以下とする必要がある。圧力が高いほど剥離状態を維持しながら還元することが可能なため、合流時の圧力は１ＭＰａ以上が好ましく、１０ＭＰａ以上がより好ましい。また、圧力が高すぎると気泡の発生や還元剤の分解の進行の可能性があるため、圧力は２５０ＭＰａ以下が好ましい。 In order to give sufficient shearing force at the time of merging, it is necessary to merge at a high pressure. On the other hand, if the pressure is too high, bubbles are generated due to a cavitation effect that causes a pressure difference in the liquid. It is necessary to do the following. Since it can reduce, maintaining a peeling state, so that a pressure is high, 1 MPa or more is preferable and the pressure at the time of joining is more preferable. In addition, if the pressure is too high, there is a possibility that bubbles are generated or the reducing agent proceeds, so that the pressure is preferably 250 MPa or less.
酸化グラフェンは還元の際に表面官能基が急速に減少する結果、非常にグラフェン同士の積層凝集が起こりやすくなる。高いせん断力をかけながら還元することにより、還元された直後に還元グラフェン同士が積層凝集を発生する前に還元グラフェン1枚の面内でπ―π相互作用により引き合い折り畳みが起こる。その結果、還元グラフェン同士の積層を防ぐことができ分散性が高まる。還元反応の完了から凝集発生までにかかる時間は非常に短いため、還元反応した後にせん断力をかけるのではなく、せん断力をかけながら還元をすることで、分散性向上効果が得られる。 In graphene oxide, the surface functional groups are rapidly reduced during the reduction, and as a result, the graphene oxide is very likely to be stacked and aggregated. By reducing while applying a high shearing force, the reduced graphenes are attracted and folded by the π-π interaction in the plane of the reduced graphene before the reduced graphenes are agglomerated and laminated immediately after the reduction. As a result, lamination of reduced graphene can be prevented and dispersibility is improved. Since the time taken from the completion of the reduction reaction to the occurrence of agglomeration is very short, the effect of improving dispersibility can be obtained by applying the shearing force instead of applying the shearing force after the reduction reaction.
合流点において加圧状態となるよう二液を合流するには、酸化グラフェン分散液と還元剤液とを、加圧送液ポンプにて流路中をそれぞれ加圧しながら送液して合流させることが好ましい。加圧送液ポンプとしては加圧能力が高く連続送液に適したプランジャーポンプが好ましい。プランジャーポンプは無脈流動作が可能な複数のプランジャーを持つ構成のポンプを用いることが好ましい。 In order to join the two liquids so as to be in a pressurized state at the confluence, the graphene oxide dispersion and the reducing agent liquid are fed together while being pressurized in the flow path by a pressurized liquid feed pump and merged. preferable. As the pressure feeding pump, a plunger pump having a high pressurizing capacity and suitable for continuous feeding is preferable. The plunger pump is preferably a pump having a plurality of plungers capable of non-pulsating flow operation.
各流路の合流地点の直前における流路径は十分高いせん断力を与えるために、３ｍｍ以下とすることが好ましく、０．５ｍｍ以下とすることがより好ましい。また流路を流れる原料の圧力損失を抑えるため、各流路の合流地点の直前における流路径は０．０５ｍｍ以上とすることが好ましく、０．１ｍｍ以上とすることがより好ましい。流路径はここでは流路の直径を表し、流路断面が円形で無い場合は、流路断面積をS、周長をLとしたとき、D＝４×S／Lを流路径とする。 また、酸化グラフェン分散液と還元剤液とを良く混合して還元反応が均一に進行するようにするため、合流直後の混合液の流れを乱流とすることが好ましい。乱流を生じさせるための方法としては、特に限定されないが、合流直後の混合液が通過する流路を直角に曲げる、合流点に撹拌板を設置する、などの方法が挙げられる。 In order to give a sufficiently high shearing force, the diameter of the flow path immediately before the merging point of each flow path is preferably 3 mm or less, and more preferably 0.5 mm or less. Moreover, in order to suppress the pressure loss of the raw material which flows through a flow path, it is preferable that the flow path diameter just before the confluence | merging point of each flow path shall be 0.05 mm or more, and it is more preferable to set it as 0.1 mm or more. The channel diameter here represents the diameter of the channel, and when the channel cross section is not circular, the channel diameter is D = 4 × S / L, where S is the channel cross-sectional area and L is the circumference. In addition, in order to mix the graphene oxide dispersion and the reducing agent solution well so that the reduction reaction proceeds uniformly, the flow of the mixed solution immediately after the merging is preferably turbulent. Although it does not specifically limit as a method for producing a turbulent flow, The method of bending the flow path through which the liquid mixture immediately after merging passes at right angles, installing a stirring plate in a merging point, etc. are mentioned.
合流後の流体が乱流になりやすいかどうかはレイノルズ数から判断でき、レイノルズ数が高いほど乱流になりやすい。レイノルズ数Reは、体積流量Q、流路の断面積をS、直径をD、液体の動粘性係数をνとしたときに、Re＝QD／Sνで表すことができる。ここで流路断面が円形で無い場合は、流路断面積をS、周長をLとしたとき、D＝４×S／Lを流路径とする。合流点直後における合流後の流体のレイノルズ数は１００以上であることが好ましく、３００以上であることがより好ましく、１０００以上であることがさらに好ましい。 It can be judged from the Reynolds number whether the fluid after joining tends to become turbulent. The higher the Reynolds number, the more likely it becomes turbulent. The Reynolds number Re can be expressed as Re = QD / Sν, where the volume flow rate Q, the cross-sectional area of the flow path is S, the diameter is D, and the kinematic viscosity coefficient of the liquid is ν. Here, when the channel cross section is not circular, when the channel cross-sectional area is S and the circumference is L, D = 4 × S / L is the channel diameter. The Reynolds number of the fluid after merging immediately after the merging point is preferably 100 or more, more preferably 300 or more, and even more preferably 1000 or more.
合流点における混合液の温度は、還元反応が起こる温度であれば特に限定されないが、還元反応促進のためには４０℃以上であることが好ましく、６０℃以上であることがより好ましい。そのため、流路に送液する前に、酸化グラフェン分散液および／または還元剤液を予め加熱することが好ましい。また、流路通過中に酸化グラフェン分散液および還元剤液の温度が低下するのを防止するため、流路中で酸化グラフェン分散液および／または還元剤液を加熱することが好ましい。これらの場合の加熱温度としては、還元反応を進める観点から４０℃以上が好ましい。また、流路内での突沸を防ぐ観点からは９０℃以下が好ましく、８０℃以下がより好ましい。なお、酸化グラフェン分散液および／または還元剤液を予め加熱しなくとも、流路内においてこれらを還元反応が進行する温度にまで加熱するようにしてもよい。 The temperature of the mixed solution at the confluence is not particularly limited as long as the reduction reaction occurs, but is preferably 40 ° C. or higher, more preferably 60 ° C. or higher for promoting the reduction reaction. Therefore, it is preferable to heat the graphene oxide dispersion and / or the reducing agent solution in advance before sending the solution to the channel. In order to prevent the temperature of the graphene oxide dispersion and the reducing agent liquid from decreasing during passage through the flow path, it is preferable to heat the graphene oxide dispersion and / or the reducing agent liquid in the flow path. The heating temperature in these cases is preferably 40 ° C. or higher from the viewpoint of proceeding the reduction reaction. Moreover, from a viewpoint of preventing bumping in a flow path, 90 degrees C or less is preferable and 80 degrees C or less is more preferable. Note that the graphene oxide dispersion liquid and / or the reducing agent liquid may be heated to a temperature at which the reduction reaction proceeds in the flow path without being heated in advance.
本発明の製造方法を実施する製造装置には湿式ジェットミルを用いることが好適である。そのような湿式ジェットミルとしてはＪＮシリーズ（株式会社常光製）、スターバースト（登録商標）シリーズ（株式会社スギノマシン製）、ナノヴェイタ（登録商標）シリーズ（吉田機械興業株式会社製）が挙げられるが、ナノヴェイタ用マイクロリアクタ（吉田機械興業株式会社製）と組み合わせたナノヴェイタが特に好適に用いることができる。 It is preferable to use a wet jet mill for the production apparatus for carrying out the production method of the present invention. Examples of such wet jet mills include the JN series (manufactured by Joko), the starburst (registered trademark) series (manufactured by Sugino Machine), and the nanoveita (registered trademark) series (manufactured by Yoshida Kikai Kogyo Co., Ltd.). In addition, a nanoveita combined with a nanoreactor microreactor (manufactured by Yoshida Kikai Kogyo Co., Ltd.) can be used particularly suitably.
〔測定例１：粉体抵抗率測定〕
サンプルの導電率は直径約２０ｍｍ、密度１ｇ／ｃｍ３のディスク状試験片に成型し、三菱化学株式会社製ＭＣＰ−ＨＴ４５０高抵抗率計とＭＣＰ−Ｔ６１０低抵抗率計を使用して測定した。
[Measurement Example 1: Powder resistivity measurement]
The conductivity of the sample was molded into a disk-shaped test piece having a diameter of about 20 mm and a density of 1 g / cm 3 , and measured using an MCP-HT450 high resistivity meter and an MCP-T610 low resistivity meter manufactured by Mitsubishi Chemical Corporation.
〔測定例２：エックス線光電子測定〕
各サンプルのエックス線光電子測定はＱｕａｎｔｅｒａ ＳＸＭ （ＰＨＩ社製））を使用して測定した。励起Ｘ線は、ｍｏｎｏｃｈｒｏｍａｔｉｃ Ａｌ Ｋα１，２ 線（１４８６．６ｅＶ）であり、Ｘ線径は２００μｍ、光電子脱出角度は４５°である。
[Measurement Example 2: X-ray photoelectron measurement]
X-ray photoelectron measurement of each sample was performed using Quantera SXM (manufactured by PHI). Excited X-rays are monochromatic Al Kα1,2 rays (1486.6 eV), the X-ray diameter is 200 μm, and the photoelectron escape angle is 45 °.
（合成例１）
酸化グラフェンの作製方法：平均粒径２５μｍ鱗片状天然黒鉛粉末（伊藤黒鉛社、品番：Ｚ-２５）を原料として、氷浴中の１０ｇの天然黒鉛粉末に、２２０ｍｌの９８％濃硫酸、５ｇの硝酸ナトリウム、３０ｇの過マンガン酸カリウムを入れ、１時間機械攪拌し、混合液の温度は２０℃以下で保持した。この混合液を氷浴から取り出し、３５℃水浴中で４時間攪拌反応し、その後イオン交換水５００ｍｌを入れて得られた懸濁液を９０℃で更に１５分反応を行った。最後に６００ｍｌのイオン交換水と５０ｍｌの過酸化水素を入れ、５分間の反応を行い、酸化グラフェン分散液を得た。熱いうちにこれを濾過し、希塩酸溶液で金属イオンを洗浄し、イオン交換水で酸を洗浄し、ｐＨが７になるまで洗浄を繰り返して酸化グラフェンゲルを作製した。作製した酸化グラフェンゲルを乾燥後エックス線光電子測定したところ、酸素原子の炭素原子に対する元素組成比（Ｏ／Ｃ比）は０．５３であった。
(Synthesis Example 1)
Preparation method of graphene oxide: Using an average particle size of 25 μm as a scale-like natural graphite powder (Ito Graphite Co., Ltd., product number: Z-25) as a raw material, 10 g of natural graphite powder in an ice bath was added to 220 ml of 98% concentrated sulfuric acid, 5 g Sodium nitrate and 30 g of potassium permanganate were added and mechanically stirred for 1 hour, and the temperature of the mixed solution was kept at 20 ° C. or lower. This mixed solution was taken out of the ice bath and reacted with stirring in a 35 ° C. water bath for 4 hours, and then a suspension obtained by adding 500 ml of ion-exchanged water was further reacted at 90 ° C. for 15 minutes. Finally, 600 ml of ion-exchanged water and 50 ml of hydrogen peroxide were added, and the reaction was performed for 5 minutes to obtain a graphene oxide dispersion. This was filtered while hot, and the metal ions were washed with dilute hydrochloric acid solution, the acid was washed with ion-exchanged water, and the washing was repeated until the pH became 7, thereby producing graphene oxide gel. When the produced graphene oxide gel was subjected to X-ray photoelectron measurement after drying, the elemental composition ratio (O / C ratio) of oxygen atoms to carbon atoms was 0.53.
（合成例２）
合成例１における硝酸ナトリウムを３．５ｇとし、過マンガン酸カリウムを２１ｇとした以外は同様に酸化グラフェンゲルを作製した。作製した酸化グラフェンゲルを乾燥後エックス線光電子測定したところ、酸素原子の炭素原子に対する元素組成比（Ｏ／Ｃ比）は０．４５であった。
(Synthesis Example 2)
A graphene oxide gel was prepared in the same manner except that the sodium nitrate in Synthesis Example 1 was 3.5 g and the potassium permanganate was 21 g. When the produced graphene oxide gel was dried and then subjected to X-ray photoelectron measurement, the elemental composition ratio (O / C ratio) of oxygen atoms to carbon atoms was 0.45.
［実施例１］
（１）酸化グラフェン分散液の調製方法：合成例１で作製した酸化グラフェンゲルをイオン交換水で、濃度５ｇ／Ｌに希釈し、超音波洗浄機で３０分処理し、均一な酸化グラフェン分散液を得た。
[Example 1]
(1) Preparation method of graphene oxide dispersion: The graphene oxide gel produced in Synthesis Example 1 is diluted with ion-exchanged water to a concentration of 5 g / L, treated with an ultrasonic cleaner for 30 minutes, and uniform graphene oxide dispersion Got.
（２）還元剤液の調製方法：還元剤として亜ジチオン酸ナトリウムをイオン交換水に溶解して１５ｍｇ／ｍｌに希釈し、還元剤液を得た。 (2) Preparation method of reducing agent solution: Sodium dithionite as a reducing agent was dissolved in ion-exchanged water and diluted to 15 mg / ml to obtain a reducing agent solution.
（３）流路径が約２００μｍであり、合流地点にて流路が直角に曲がる乱流発生機構を有するマイクロリアクタを装着した湿式ジェットミルであるナノヴェイタＬ−ＥＤ（吉田機械興業株式会社製）にて、（１）で調製した酸化グラフェン分散液および（２）で調製した還元剤液予め４０℃に加熱した後、マイクロリアクタ内流路にプランジャーポンプを用いてそれぞれ２０ＭＰａの吐出圧力で送液し、２０ＭＰａの加圧下で、マイクロリアクタ内流路の合流点で１：１の割合で合流させた。各流路は温度を４０℃に保ち、酸化グラフェン分散液と還元剤液とを加熱した状態で送液した。合流後の混合液は、酸化グラフェンの茶色ではなく、グラフェンの黒色が見られ、還元されていることが目視で観察された。 (3) Nanoweta L-ED (manufactured by Yoshida Kikai Kogyo Co., Ltd.), which is a wet jet mill equipped with a microreactor having a turbulent flow generation mechanism that has a channel diameter of about 200 μm and the channel bends at a right angle at the junction. The graphene oxide dispersion prepared in (1) and the reducing agent solution prepared in (2) were heated to 40 ° C. in advance, and then sent to the microreactor flow path at a discharge pressure of 20 MPa using a plunger pump, Under a pressure of 20 MPa, the cells were merged at a ratio of 1: 1 at the merge point of the channels in the microreactor. Each channel was kept at a temperature of 40 ° C., and the graphene oxide dispersion and the reducing agent liquid were fed in a heated state. In the mixed solution after the merging, not the brown graphene oxide but the black graphene was seen, and it was visually observed that it was reduced.
この還元グラフェン分散液を１ｇ／ＬにＮＭＰで希釈した後に沈降状態を目視観察したところ１０日後も沈降は見られなかった。 When this reduced graphene dispersion was diluted with NMP to 1 g / L and the sedimentation state was visually observed, no sedimentation was observed even after 10 days.
さらに、当該還元グラフェン分散液を水にてろ過洗浄後、再度イオン交換水に５ｇ／Ｌに分散し凍結乾燥してグラフェン粉末を得た。このグラフェン粉末を測定例１に従い粉体抵抗率を測定したところ０．０１５Ω・ｃｍであった。また、測定例２に従いエックス線光電子測定をしたところ、酸素原子の炭素原子に対する元素組成比（Ｏ／Ｃ比）は０．０８であった。 Further, the reduced graphene dispersion was filtered and washed with water, then again dispersed in ion-exchanged water at 5 g / L, and freeze-dried to obtain graphene powder. When the powder resistivity of this graphene powder was measured according to Measurement Example 1, it was 0.015 Ω · cm. Further, when X-ray photoelectron measurement was performed according to Measurement Example 2, the elemental composition ratio (O / C ratio) of oxygen atoms to carbon atoms was 0.08.
［実施例２］
（１）酸化グラフェン分散液の調製方法：合成例１で作製した酸化グラフェンゲルをイオン交換水で、濃度５ｇ／Ｌに希釈し、超音波洗浄機で３０分処理し、均一な酸化グラフェン分散液を得た。
[Example 2]
(1) Preparation method of graphene oxide dispersion: The graphene oxide gel produced in Synthesis Example 1 is diluted with ion-exchanged water to a concentration of 5 g / L, treated with an ultrasonic cleaner for 30 minutes, and uniform graphene oxide dispersion Got.
（２）還元剤液の調製方法：還元剤として亜ジチオン酸ナトリウムをイオン交換水に溶解して１５ｇ／Ｌに希釈し、還元剤液を得た。 (2) Preparation method of reducing agent solution: Sodium dithionite as a reducing agent was dissolved in ion-exchanged water and diluted to 15 g / L to obtain a reducing agent solution.
（３）各流路の吐出圧力を１０ＭＰａとし、合流点において１０ＭＰａの加圧下で合流させたこと以外は実施例１の（３）と同様にして、酸化グラフェン分散液と還元剤液とを合流させた。 (3) The graphene oxide dispersion liquid and the reducing agent liquid are merged in the same manner as in (3) of Example 1 except that the discharge pressure of each flow path is 10 MPa and the flow is merged under a pressure of 10 MPa at the merge point. I let you.
得られた還元グラフェン分散液を１ｇ／ＬにＮＭＰで希釈した後に沈降状態を目視観察したところ１０日後も沈降は見られなかった。 When the obtained reduced graphene dispersion was diluted with NMP to 1 g / L and the sedimentation state was visually observed, no sedimentation was observed even after 10 days.
さらに、当該還元グラフェン分散液を水にてろ過洗浄後、再度イオン交換水に５ｇ／Ｌに分散し凍結乾燥してグラフェン粉末を得た。このグラフェン粉末を測定例１に従い粉体抵抗率を測定したところ０．０２１Ω・ｃｍであった。また、このグラフェン粉末を測定例２に従いエックス線光電子測定をしたところ、Ｏ／Ｃ比は０．０９であった。 Further, the reduced graphene dispersion was filtered and washed with water, then again dispersed in ion-exchanged water at 5 g / L, and freeze-dried to obtain graphene powder. When the powder resistivity of this graphene powder was measured according to Measurement Example 1, it was 0.021 Ω · cm. Further, when this graphene powder was subjected to X-ray photoelectron measurement according to Measurement Example 2, the O / C ratio was 0.09.
［実施例３］
（１）酸化グラフェン分散液の調製方法：合成例１で作製した酸化グラフェンゲルをイオン交換水で、濃度５ｇ／Ｌに希釈し、超音波洗浄機で３０分処理し、均一な酸化グラフェン分散液を得た。
（２）還元剤液の調製方法：還元剤液としてはベンジルアルコールを用いた。
（３）酸化グラフェン分散液および還元剤液をともに８０℃に加熱し、流路も８０℃に保った状態とした以外は実施例１の（３）と同様にして、酸化グラフェン分散液と還元剤液とを合流させた。合流後の混合液は、酸化グラフェンの茶色ではなく、グラフェンの黒色が見られ還元されていることが目視で観察された。
[Example 3]
(1) Preparation method of graphene oxide dispersion: The graphene oxide gel produced in Synthesis Example 1 is diluted with ion-exchanged water to a concentration of 5 g / L, treated with an ultrasonic cleaner for 30 minutes, and uniform graphene oxide dispersion Got.
(2) Preparation method of reducing agent solution: Benzyl alcohol was used as the reducing agent solution.
(3) The graphene oxide dispersion and the reducing agent liquid were both heated to 80 ° C. and the flow path was kept at 80 ° C., in the same manner as in (3) of Example 1 and reduced. The chemical solution was merged. It was visually observed that the mixed solution after the merging was not graphene oxide brown but graphene black and was reduced.
この還元グラフェン分散液を１ｇ／ＬにＮＭＰで希釈した後に沈降状態を目視観察したところ１０日後も沈降は見られなかった。 When this reduced graphene dispersion was diluted with NMP to 1 g / L and the sedimentation state was visually observed, no sedimentation was observed even after 10 days.
また、当該還元グラフェン分散液を水にてろ過洗浄後、再度イオン交換水に５ｇ／Ｌに分散し凍結乾燥してグラフェン粉末を得た。このグラフェン粉末を測定例１に従い粉体抵抗率を測定したところ０．０３０Ω・ｃｍであった。また、このグラフェン粉末を測定例２に従い、エックス線光電子測定をしたところ、Ｏ／Ｃ比は０．１１であった。 Further, the reduced graphene dispersion was filtered and washed with water, then again dispersed in ion-exchanged water at 5 g / L, and freeze-dried to obtain graphene powder. When the powder resistivity of this graphene powder was measured according to Measurement Example 1, it was 0.030 Ω · cm. Further, when this graphene powder was subjected to X-ray photoelectron measurement according to Measurement Example 2, the O / C ratio was 0.11.
［実施例４］
実施例１において使用する酸化グラフェンを合成例１の酸化グラフェンゲルの替わりに合成例２の酸化グラフェンゲルを使用し、他は実施例１と同様の処理を実施し還元グラフェン分散液を得た。
[Example 4]
The graphene oxide used in Example 1 was replaced with the graphene oxide gel of Synthesis Example 1 in place of the graphene oxide gel of Synthesis Example 2, and the other processes were performed in the same manner as in Example 1 to obtain a reduced graphene dispersion.
得られた還元グラフェン分散液を１ｇ／ＬにＮＭＰで希釈した後に沈降状態を目視観察したところ１０日後も沈降は見られなかった。 When the obtained reduced graphene dispersion was diluted with NMP to 1 g / L and the sedimentation state was visually observed, no sedimentation was observed even after 10 days.
さらに、当該還元グラフェン分散液を水にてろ過洗浄後、再度イオン交換水に５ｇ／Ｌに分散し凍結乾燥してグラフェン粉末を得た。このグラフェン粉末を測定例１に従い粉体抵抗率を測定したところ０．０１３Ω・ｃｍであった。また、測定例２に従いエックス線光電子測定をしたところ、酸素原子の炭素原子に対する元素組成比（Ｏ／Ｃ比）は０．０７であった。 Further, the reduced graphene dispersion was filtered and washed with water, then again dispersed in ion-exchanged water at 5 g / L, and freeze-dried to obtain graphene powder. The graphene powder was measured for powder resistivity according to Measurement Example 1 and found to be 0.013 Ω · cm. Further, when X-ray photoelectron measurement was performed according to Measurement Example 2, the elemental composition ratio (O / C ratio) of oxygen atoms to carbon atoms was 0.07.
［比較例１］
実施例１の（１）で調製した酸化グラフェン分散液１００ｍｌおよび還元剤液１００ｍｌを、４０℃に加熱して、ビーカー内で、ホットプレートスターラーで３００ｒｐｍで攪拌しながら、４０℃に加熱し、1時間反応させた。還元により酸化グラフェンの茶色からグラフェンの黒色に変化している様子が目視にて観察された。
[Comparative Example 1]
The graphene oxide dispersion 100 ml and the reducing agent solution 100 ml prepared in (1) of Example 1 were heated to 40 ° C. and heated to 40 ° C. in a beaker while stirring at 300 rpm with a hot plate stirrer. Reacted for hours. It was visually observed that the graphene oxide was changed from brown to graphene black by reduction.
得られた還元グラフェン分散液を１ｇ／ＬにＮＭＰで希釈した後に沈降状態を目視観察したところ1時間後に沈降が見られた。 When the obtained reduced graphene dispersion was diluted with NMP to 1 g / L and the sedimentation state was visually observed, sedimentation was observed after 1 hour.
また、当該還元グラフェン分散液を水にてろ過洗浄後、再度イオン交換水に５ｇ／Ｌに分散し凍結乾燥してグラフェン粉末を得た。このグラフェン粉末を測定例１に従い粉体抵抗率を測定したところ０．０３５Ω・ｃｍであった。また、このグラフェン粉末を測定例２に従い、エックス線光電子測定をしたところ、Ｏ／Ｃ比は０．１２であった。 Further, the reduced graphene dispersion was filtered and washed with water, then again dispersed in ion-exchanged water at 5 g / L, and freeze-dried to obtain graphene powder. The powder resistivity of this graphene powder was measured according to Measurement Example 1 and found to be 0.035 Ω · cm. Further, when this graphene powder was subjected to X-ray photoelectron measurement according to Measurement Example 2, the O / C ratio was 0.12.
［比較例２］
実施例３の（１）で調製した酸化グラフェン分散液１００ｍｌおよび還元剤液１００ｍｌを、８０℃に加熱して、ビーカー内で、ホットプレートスターラーで３００ｒｐｍで攪拌しながら、８０℃に加熱し、1時間反応させた。
[Comparative Example 2]
The graphene oxide dispersion liquid 100 ml and the reducing agent liquid 100 ml prepared in Example 3 (1) were heated to 80 ° C. and heated to 80 ° C. in a beaker while stirring at 300 rpm with a hot plate stirrer. Reacted for hours.
反応後もほとんど酸化グラフェンに変色が見られず、還元反応が十分起こっていないことが目視にて観察された。 Even after the reaction, almost no discoloration was observed in the graphene oxide, and it was visually observed that the reduction reaction did not occur sufficiently.
このグラフェン分散液を１ｇ／ＬにＮＭＰで希釈した後に沈降状態を目視観察したところ１０日後も沈降は見られなかった。 When the graphene dispersion was diluted with NMP to 1 g / L and the sedimentation state was visually observed, no sedimentation was observed even after 10 days.
また、当該分散液を水にてろ過洗浄後、再度イオン交換水に５ｇ／Ｌに分散し凍結乾燥してグラフェン粉末を得た。このグラフェン粉末を測定例１に従い粉体抵抗率を測定したところ測定できないほど高抵抗であった。また、このグラフェン粉末を測定例２に従い、エックス線光電子測定をしたところ、Ｏ／Ｃ比は０．５０であった。 The dispersion was filtered and washed with water, then again dispersed in ion exchange water at 5 g / L and freeze-dried to obtain graphene powder. When the powder resistivity of this graphene powder was measured according to Measurement Example 1, it was so high that it could not be measured. Further, when this graphene powder was subjected to X-ray photoelectron measurement in accordance with Measurement Example 2, the O / C ratio was 0.50.
各実施例、比較例における還元グラフェンの作製方法および得られた還元グラフェンの物性を表１に示す。 Table 1 shows a method for producing reduced graphene and physical properties of the obtained reduced graphene in each Example and Comparative Example.
Claims (14)
The manufacturing method of the reduced graphene in any one of Claims 1-13 implemented using a wet jet mill.
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