Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/182—Graphene
  • C01B32/194—After-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/182—Graphene
  • C01B32/184—Preparation
  • C01B32/19—Preparation by exfoliation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/182—Graphene
  • C01B32/194—After-treatment
  • C01B32/196—Purification
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2204/00—Structure or properties of graphene
  • C01B2204/04—Specific amount of layers or specific thickness

Definitions

• the present invention relates to a process for preparing graphene solutions by alkali metal salts, graphene solutions, processes for producing graphene-alkali metal salts, graphene-alkali metal salts, and graphene composite materials, and to processes for producing the graphene composite materials.
• Graphene are two-dimensional carbon crystals that are constructed analogously to individual graphite layers.
• the carbon atoms are arranged in a hexagonal honeycomb structure. This arrangement results from the hybridization ("fusion") of the 2s, 2px and 2py orbitals of the participating carbon atoms to so-called sp 2 hybrid orbitals
• Graphene has metallic and non-metallic properties
• the metallic properties of graphene are related to good electrical and thermal conductivity
• the non-metallic properties provide high thermal stability, chemical inertness and lubricity of these compounds, making Graphene suitable for a variety of engineering applications such as batteries, fuel cells or refractories.
• the first graphene flakes were made by Novoselov [K. S. Novoselov, et al .; Science. 306, No. 5696, 2004, pp. 666-669] by exfoliation of HOPG (Highly Oriented Pyrolytic Graphite).
• HOPG Highly Oriented Pyrolytic Graphite
• adhesive tape was pressed onto the HOPG and then removed; while graphite remains in the adhesive back.
• the adhesive strip is pressed onto a silicon wafer with a thin silicon dioxide layer and pulled off again. Thereafter, graphene becomes visible by suitable optical methods. This method is very time consuming and you get high quality but very few samples.
• Another method relates to the production of graphene oxide by strongly oxidizing agents.
• the graphene oxide generated by this method is morphologically similar to a graphene layer, but chemically differs from graphene due to the fully oxidized state.
• toxic and non-hazardous liquid hydrazine it is possible to further reduce the graphene oxide generated by this method to finally obtain graphene [Stakovich, S. et al. Jour. of Mat. Chem. 2006, 16; 155-158].
• the object of the present invention was therefore to provide such a novel process for the preparation of graphene.
• the object is achieved by providing a method for producing a graphene solution in which graphite is reduced with an alkali metal salt in a polar organic solvent.
• One advantage of the method is, inter alia, the avoidance of the use of toxic, non-hazardous and expensive agents for the preparation of the graphene solution. Even a thermal treatment with temperatures from 700 ° C to 1200 ° C, as they are described for certain chemical exfoliation methods, is not necessary.
• Another advantage of the present inventive method lies in the scalability and the associated ability to produce graphene on an industrial scale. Further, the method of the invention also enables the production of graphene having a layer thickness of less than 20 nanometers, i. to graphene with only one graphene sheet layer (0.34 nm). The layer thickness can be precisely controlled by the process according to the invention via the amount of reducing agent added (see FIG. 2).
• a + B characterized in that A + is a cation of an alkali metal ion, preferably lithium or sodium and
• B is an anion of a polyaromatic compound.
• a polyaromatic compound is used as the anion.
• these include naphthalene, anthracene, carbazole, perylene, phenanthrene, coronene, chrysene, triphenylene, fluorenone, benzophenone and / or anthraquinone. Particularly preferred is the use of naphthalene.
• Suitable polar organic solvents for the process for preparing a graphene solution are in particular tetrahydrofuran (THF), acetonitrile, 1,2-dimethoxyethane (DME), diethylene glycol diethyl ether, tri- or tetraethylene glycol dimethyl ether, sulfolane (tetramethylene sulfone), tetramethylene sulfoxide (TMSO).
• THF tetrahydrofuran
• DME 1,2-dimethoxyethane
• DME 1,2-dimethoxyethane
• diethylene glycol diethyl ether diethylene glycol diethyl ether
• tri- or tetraethylene glycol dimethyl ether tri- or tetraethylene glycol dimethyl ether
• sulfolane tetramethylene sulfone
• TMSO tetramethylene sulfoxide
• N N-diethylacetamide, ⁇ , ⁇ -dimethylacetamide (DMAc), ⁇ , ⁇ -dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethylsulfone, diphenylsulfoxide, diphenylsulfone, tetramethylurea, tetra-n-butylurea , 1,3-dimethylimidazolidin-2-one (DMI), other glycol ethers or mixtures thereof.
• Preferred organic solvents are glycol ethers such as 1,2-dimethoxyethane (DME), diethylene glycol diethyl ether, tri- or tetraethylene glycol dimethyl ether or mixtures thereof.
• the polyaromatic compound is preferably first dissolved in the polar organic solvent (preferably anhydrous), preferably in a quantitative ratio of from 10 mM (1: 100) to 1: 1 (IM), preferably with stirring. Thereafter, this solution is the alkali metal, preferably in slight stoichiometric excess, i. in a quantitative ratio to the solution of 11 mM to 1.1M supplied.
• the alkali metal is preferably supplied in as small as possible pieces (e.g., by cutting a wire, etc.) to facilitate the dissolution of the alkali metal.
• the solution thus obtained is preferably heated to a temperature of 60 ° C to 120 ° C for a period of preferably 15 minutes to 2 hours to accelerate the dissolution of the alkali metal. If the solution thus obtained, which is also referred to below as "reducing agent", is not used immediately, it can be cooled and stored for a long time for later use.
• graphite is now added to the novel process for the preparation of the graphene solution, preferably with stirring.
• Particularly suitable is the use of graphite finely ground as possible, which can be obtained in particular by the mechanical processing techniques generally known in the art.
• a fine as possible Ground graphite supports the exfoliation and dissolution step. This step is carried out until a stable graphene solution is obtained in which as far as possible no deposits are visible.
• the processes according to the invention are preferably carried out with a ratio of graphite to the alkali metal of less than 4000 g of graphite per mole of alkali metal and preferably less than 20 g of graphite per mole of alkali metal.
• inert conditions refers to conditions which are characterized by the fact that as little or as possible no water or oxygen comes into contact with the agents used for the inventive method for producing the graphene solution or solutions and compounds resulting therefrom This can be ensured by carrying out the process according to the invention preferably in an inert gas space which can be closed in a substantially gas-tight manner and filled with an inert gas atmosphere (such as nitrogen or argon), such as a glovebox, etc.
• an inert gas atmosphere such as nitrogen or argon
• Another object of the present invention relates to a solution - referred to in this application as "graphene solution” - in which (negatively charged) graphene, a polyaromatic compound and a (positively charged) alkali metal are dissolved in a polar organic solvent such graphene solution of poly aromatic compounds, alkali metals and polar organic solvents have already been described above
• graphene solution prepared by the graphene solution preparation method described above Graphene solutions are preferably used stored under inert conditions.
• the present invention also relates to a process for producing a graphene-alkali metal salt by evaporation of the solvent of the graphene solution according to the invention.
• Apparatus or processes suitable for evaporation such as, for example, a rotary evaporator, are known to the person skilled in the art.
• the polyaromatic compound for example, when using naphthalene, preferably also evaporated.
• other extraction methods known in the art can be used to optionally remove the polyaromatic compounds.
• Another object of the present invention is also a Graphen- alkali metal salt, which can be prepared by such a method.
• Another object of the invention relates to a process for the preparation of a graphene solution - hereinafter referred to as "purified graphene solution" - in which the graphene alkali metal salt, which is prepared by the above-described method for producing a graphene alkali metal salt by evaporation of the solvent may be dissolved in an aprotic organic solvent, preferably under inert conditions and preferably in a ratio to the graphene alkali metal salt of 1: 100 to 1: 1.
• Suitable aprotic organic solvents are in particular aprotic-polar organic solvents and therefore preferably those again, above
• the advantage of this process step lies in particular in the fact that, with regard to further processing steps, one has the opportunity of selecting the graphene in another, suitable for further processing solvents, to be dissolved.
• the graphene alkali metal salt can also be dissolved in a solvent suitable for the substance to be added in this step.
• the alkali metal salt is preferably dissolved in DMF because polystyrene also dissolves well in DMF.
• the person skilled in the art is aware of which aprotic organic solvents he must use in each case for the specific fields of application of the purified graphene solution.
• the invention also relates to a purified graphene solution prepared by this process. Such purified graphene solution is preferably further stored under inert conditions until use.
• the neutral character of the graphs can be restored by exposing the graphene solution or the purified graphene solution to air or water.
• This may be useful in connection with the use of the graphene solution or the graphene solution with other polymers and in particular in the production of polymer fibers.
• the graphite salt may be transformed into pure graphene within the polymer or spun polymer fiber upon contact with air or water, for example, at the ripening step of the spun polymer fiber.
• the graphene solution according to the invention or the purified graphene solution according to the invention can also be used, for example, to functionalize surfaces of materials and in particular of polymers.
• the surfaces of these materials are impregnated with the solutions according to the invention, coated or printed.
• electrical materials such as silicon wafers can be coated or printed with the graphene solution or graphene solution to produce new microelectronic components such as transistors (with graphene electrical circuits).
• the graphene solution or the purified graphene solution make it particularly easy to process them especially interesting for use with conventional printing techniques and microlithography.
• a further process according to the invention describes the production of a composite material using the graphene solution according to the invention or the purified graphene solution according to the invention and the addition of another substance, preferably with stirring, and the subsequent further processing to the composite material with a suitable production process.
• Suitable substances that can be added to the graphene solution or the purified graphene solution are, for example, plastics, metals or ceramic materials. These are added in a proportion to the graphene solution, so that a composite having a graphene content by weight of preferably less than 10%, and more preferably less than 5%, and most preferably equal to or less than 2%, is added thereto. , preferably between 0, 1 and 1%, is formed.
• suitable plastics for the composite material according to the invention are nylon, polyvinyl chloride, poly (methyl) methacrylate, polystyrene, polyethylene, polypropylene, polystyrene, polycarbonate, epoxy resins, polyfluorinated hydrocarbons, polyimides, polyamides, fluorinated polymers, acrylamides, polyesters, cyanate esters and mixtures thereof.
• Suitable metals are in particular aluminum, magnesium, titanium and their alloys. Alloys with copper such as brass or bronze are suitable for the production of the composite material according to the invention.
• Suitable ceramic materials are, for example, oxide ceramics such as aluminum oxide or beryllium oxide, non-oxide ceramics such as silicon carbide, boron nitride, boron carbide or composite ceramics.
• Suitable substances are preferably added in powder form or as fine-grained granules to the graphene solution or purified graphene solution.
• Suitable manufacturing processes are, in particular, heat treatment processes, such as, for example, sintering.
• the graphene solution or purified graphene solution mixed with the additional substance is exposed to an oxygen environment and heat-treated at a suitable temperature and pressure.
• the appropriate conditions depend on the added substance (and not on graphene). For example, when using a metal or alloy, the temperature should be close to but below the melting temperature of the metal or alloy. The person skilled in the art knows which factors he has to take into account, depending on the substances used.
• Another object of the present invention are also composite materials that can be produced by the method described above for producing the composite materials.
• the composite materials according to the invention can be used, for example, for thermally and / or electrically conductive products.
• Exemplary application find the composite materials according to the invention in batteries, capacitors, paints, varnishes or catalysts. The person skilled in the art knows for which further applications he can use the described composite materials.
• Figure 1 Exemplary representation of a purified according to the invention
• THF THF
• Graphene layer can be obtained in the graphene solution according to the invention.
• Step 1 Preparation of the reducing agent
• the reducing agent is prepared by dissolving 384 mg of naphthalene (3 mmol) in 100 ml of anhydrous THF with stirring in a round-bottomed flask and then adding metallic lithium in slight stoichiometric excess (about 30 mg) to the solution. To facilitate the dissolution of the alkali metal, the alkali metal should be supplied in as small as possible pieces. The mixture is then flashed for about 2 to 3 hours under reflux to the boiling point of THF (66 ° C). During this time, the alkali metal dissolves in the naphthalene / THF solution (visible by size reduction of the alkali metal particles) and the mixture turns dark green (typical of Li naphthalene complexes). The reducing agent is cooled and reused. Step 2: Dissolve the graphite material
• Step 3 Preparation of a Graphene Lithium Salt
• a graphene-lithium salt solid can be purified by evaporating the THF solvent by a rotary evaporator or other means known and usable. The resulting solid is dissolved under an inert atmosphere in a polar aprotic organic solvent such as THF, DMF, DMSO, DME or other glycol ethers and used for its intended purpose.
• a polar aprotic organic solvent such as THF, DMF, DMSO, DME or other glycol ethers

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• 2009
  • 2009-11-12 DE DE102009052933A patent/DE102009052933A1/de not_active Withdrawn
• 2010
  • 2010-11-08 EP EP10775815A patent/EP2499095A1/de not_active Withdrawn
  • 2010-11-08 US US13/508,189 patent/US20120256121A1/en not_active Abandoned
  • 2010-11-08 JP JP2012538297A patent/JP2013510787A/ja active Pending
  • 2010-11-08 WO PCT/EP2010/067008 patent/WO2011057985A1/de active Application Filing
  • 2010-11-08 KR KR1020127012193A patent/KR20120095907A/ko not_active Application Discontinuation
  • 2010-11-08 CN CN2010800514433A patent/CN102656114A/zh active Pending
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