JP2019507715A - Graphene-carbon hybrid foam - Google Patents

Abstract

An integrated 3D graphene-carbon hybrid foam composed of a plurality of pores and pore walls, wherein the pore walls are chemically modified by a carbon material having a carbon material to graphene weight ratio of 1/100 to 1/2. A graphene sheet comprising 2 to 10 layers of stacked graphene planes comprising coupled single-layer or few-layer graphene sheets, the few-layer graphene sheets having an interplanar spacing doo2 of 0.3354 nm to 0.40 nm; The pure graphene material having 0% non-carbon element, or the impure graphene material having 0.01% to 25% by weight non-carbon element, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride Graphene Chloride, Graphene Bromide, Graphene Iodide, Graphene Hydrogenated, Graphitized Graphite, Doped Graph Emissions, chemical functionalization graphene, or combinations thereof, integrated 3D graphene - carbon hybrid foam is provided. Also provided are methods of making the hybrid form, products comprising the hybrid foams of the invention, and applications. [Selected figure] 2A

Description

Cross-Reference to Related Applications This application is related to US patent application Ser. No. 14 / 998,356, filed Dec. 28, 2015 and US patent application Ser. No. 14/998, each of which is incorporated herein by reference. Claim the priority of the specification, 357.

  FIELD OF THE INVENTION The present invention relates generally to the field of carbon / graphite foams, and in particular, to new forms of porous graphite materials, referred to herein as integral 3D graphene-carbon hybrid foams, methods of making the same, and articles comprising the same It relates to how to operate the product.

  Carbon has five unique crystal structures including diamond, fullerene (0D nanographite material), carbon nanotubes or carbon nanofibers (1D nanographite material), graphene (2D nanographite material), and graphite (3D graphite material) It is known to have. Carbon nanotube (CNT) refers to a tubular structure grown in a single layer or multiple layers. Carbon nanotubes (CNT) and carbon nanofibers (CNF) have a diameter of several nanometers to several hundreds of nanometers. These longitudinal hollow structures impart unique mechanical, electrical and chemical properties to the material. CNTs or CNFs are one-dimensional nanocarbon or 1D nanographitic materials.

  Our research group was a pioneer in the development of graphene materials and related manufacturing methods in 2002: (1) B.1. Z. Jang and W. C. Huang, "Nano-scaled Graphene Plates", U.S. Patent No. 7,071,258 (07/04/2006), filed October 21, 2002; Z. Jang et al., "Process for Producing Nano-scaled Graphene Plates", U.S. Patent Application No. 10 / 858,814 (06/03/2004); Z. Jang, A. Zhamu, and J.A. Guo, "Process for Producing Nano-scaled Platelets and Nanocomposites", US Patent Application No. 11 / 509,424 (08/25/2006).

  Single-layer graphene sheets are composed of carbon atoms that occupy a two-dimensional hexagonal lattice. Multilayer graphene is a platelet composed of two or more graphene planes. Individual single layer graphene sheets and multilayer graphene platelets are collectively described herein as nanographene platelets (NGP) or graphene materials. For NGP, pure graphene (essentially 99% carbon atoms), slightly oxidized graphene (<5% by weight oxygen), graphene oxide (≧ 5% by weight oxygen), slightly fluorinated graphene (<5 wt% fluorine), graphene fluoride (((5 wt% fluorine), other halogenated graphene, and chemically functionalized graphene.

  NGP has been found to have a series of unique physical, chemical and mechanical properties. For example, graphene has been found to exhibit the highest intrinsic strength and the highest thermal conductivity of any existing materials. Graphene's actual electronic device applications (eg, substitution of Si as a key element in transistors) are not expected to be realized in the next 5-10 years, but in composites and electrodes of energy storage devices Its use as a nanofiller in materials is imminent. The ability to utilize processable graphene sheets in large quantities is important for the successful development of graphene composite applications, energy applications, and other applications.

  Our research group first discovered graphene [B. Z. Jang and W. C. Huang, "Nano-scaled Graphene Plates", U.S. Patent Application No. 10 / 274,473, filed October 21, 2002; now U.S. Patent No. 7,071,258 (07/04 / 2006)]. Methods for producing NGP and NGP nanocomposites have recently been reviewed by the present inventors [Bor Z. Jang and A Zhamu, "Processing of Nano Graphene Platelets (NGPs) and NGP Nanocomposites: A Review," J. Am. Materials Sci. 43 (2008) 5092-5101]. Four major prior art methods have been employed to produce NGP. These advantages and disadvantages are briefly summarized below.

Review method 1 for the preparation of isolated nano-graphene plates or sheets (NGP) Method 1: Chemical formation and reduction of graphene oxide (GO) The first method (Figure 1) is a Graphite Intercalation Compound (GIC), or indeed In order to obtain graphite oxide (GO), the treatment of natural graphite powder with an intercalant and an oxidizing agent (for example, concentrated sulfuric acid and nitric acid, respectively) [William S. Hummers, Jr. , Et al. , Preparation of Graphitic Oxide, Journal of the American Chemical Society, 1958, p. 1339]. Before intercalation or oxidation, the graphite has a graphene interplanar spacing of about 0.335 nm (Ld = 1/2 d ₀₀₂ = 0.335 nm). With intercalation and oxidation treatments, the graphene spacing typically increases to values above 0.6 nm. This is the first expansion stage that occurs in the graphite material during this chemical path. The resulting GIC or GO is then further expanded (sometimes referred to as exfoliation) using either thermal shock exposure, or solution based ultrasonic assisted graphene layer exfoliation methods.

  In thermal shock exposure methods, high temperatures are typically applied to GIC or GO to form exfoliated or further expanded graphite, which is typically still in the form of a "graphite worm" composed of graphite flakes interconnected with one another. Is exposed to a short time (typically 15 to 60 seconds) to 800 to 1,050.degree. C. to peel or expand GIC or GO. This thermal bombardment procedure can produce partially separated graphite flakes or graphene sheets, but usually the majority of the graphite flakes remain interconnected. Typically, the exfoliated graphite or graphite worm is then subjected to a flake separation process using air milling, mechanical shear, or sonication in water. Thus, method 1 basically involves three different procedures: first expansion (oxidation or intercalation), further expansion (or "peeling"), and separation.

  In the solution-based separation method, the expanded or exfoliated GO powder is dispersed in water or an aqueous alcohol solution and subjected to ultrasonication. In these methods, sonication occurs after graphite intercalation and oxidation (i.e. after the first expansion), and typically after thermal shock exposure of the resulting GIC or GO (second It is important to note that it is used after Alternatively, ion exchange or long-time purification of GO powder dispersed in water so that the repulsive force between ions existing in the interplanar space overcomes the inter-graph van der Waals force and as a result, the graphene layer separates. The procedure is done.

There are several major problems associated with this conventional chemical manufacturing method:
(1) This method requires the use of large amounts of sulfuric acid, nitric acid, and some undesirable chemicals such as potassium permanganate or sodium chlorate.
(2) Chemical treatment methods require a long time of intercalation and oxidation, typically 5 hours to 5 days.
(3) The strong acid consumes large amounts of graphite during this long intercalation or oxidation process by "entering into graphite" (graphite is converted to carbon dioxide which is lost during the process). It is not uncommon for 20 to 50% by weight of graphite material immersed in strong acid and oxidant to be lost.
(4) Thermal exfoliation is a process that requires high temperatures (typically 800-1200 ° C.) and is therefore very energy consuming.
(5) Both heat-induced and solution-induced peeling methods require very time-consuming washing and purification steps. For example, 2.5 kg of water is typically used to wash and recover 1 gram of GIC, resulting in a large amount of wastewater that requires proper treatment.
(6) In both heat- and solution-induced stripping methods, the resulting product is a GO platelet that needs to be subjected to an additional chemical reduction treatment to reduce the oxygen content. is there. Typically, even after reduction, the conductivity of the GO platelets remains much lower than that of pure graphene. Furthermore, this reduction procedure often involves the use of toxic chemicals such as hydrazine.
(7) Furthermore, the amount of intercalation solution retained on the flakes after drainage is in the range of 20 to 150 parts by weight (pph) of solution per 100 parts by weight of graphite flakes, more typically about 50 to 120 pph It can be in the range of During hot exfoliation, the remaining intercalate species retained by the flakes decompose to form various chemical species of sulfur and nitrogen compounds (eg, NO _x and SO _x ) which are undesirable. Effluents require costly remediation procedures to ensure that they do not adversely affect the environment.

  The present invention was made to overcome the limitations or problems outlined above.

Method 2: Direct Formation of Pure Nano-Graphene Platelets In 2002, our team of researchers have studied monolayers and multilayers from partially carbonized or graphitized polymer carbons obtained from polymers or pitch precursors. Succeeded in isolating graphene sheets of [B. Z. Jang and W. C. Huang, "Nano-scaled Graphene Plates", U.S. Patent Application No. 10 / 274,473, filed October 21, 2002; now U.S. Patent No. 7,071,258 (07/04 / 2006)]. Mack et al. ["Chemical manufacture of nanostructured materials", US Pat. No. 6,872,330 (Mar. 29, 2005)] intercalates graphite with a potassium melt and as a result K intercalates Contacting the carbonated graphite with an alcohol to produce rough exfoliated graphite comprising NGP. This method needs to be performed carefully in vacuum or in a very dry glove box environment, as pure alkali metals such as potassium and sodium are very sensitive to moisture and pose an explosion hazard. This method is not suitable for mass production of NGP. The present invention was made to overcome the limitations outlined above.

Method 3: Epitaxial Growth and Chemical Vapor Deposition of Nano-graphene Sheets on Inorganic Crystal Surfaces Small-scale production of ultra-thin graphene sheets on substrates can be performed by thermal growth based epitaxial growth and laser desorption ionization techniques [Walt A. DeHeer, Claire Berger, Phillip N. First, "Patterned thin film devices and methods for making same", U.S. Patent No. 7,327,000 B2 (June 12, 2003)]. Epitaxial films of graphite having only one or several atomic layers are of technical and chemical importance because of their unique properties and their great potential as device substrates. However, these methods are not suitable for mass production of isolated graphene sheets for composite materials and energy storage applications. The present invention was made to overcome the limitations outlined above.

Another method of producing graphene in thin film form (typically <2 nm thickness) is a catalytic chemical vapor deposition method. This catalytic CVD involves catalytic decomposition of a hydrocarbon gas (eg, C ₂ H ₄ ) on the surface of Ni or Cu to form monolayer or few-layer graphene. Since Ni or Cu is a catalyst, carbon atoms obtained by decomposition of hydrocarbon gas molecules at a temperature of 800 to 1,000 ° C. may be deposited directly on the Cu foil surface or from a Ni-C solid solution state to a Ni foil Deposited on the surface, a sheet of single layer or few layers of graphene (less than 5 layers) is formed. Ni or Cu catalyzed CVD processes are not suitable for deposition of more than 5 graphene planes (typically <2 nm), beyond which the underlying Ni or Cu layer is no longer catalytically viable It will not be possible. CVD graphene films are very expensive.

Method 4: Bottom-up method (synthesis of graphene from small molecules)
Yang et al ["Two-dimensional Graphene Nano-ribbons," J. Mol. Am. Chem. Soc. 130 (2008) 4216-17] is the longest using the method starting from the Suzuki-Miyaura coupling of 1,4-diiodo-2,3,5,6-tetraphenyl-benzene with 4-bromophenylboronic acid A nanographene sheet with a length of 12 nm was synthesized. The hexaphenylbenzene derivative obtained as a result was further derivatized to condense the ring to obtain a small graphene sheet. This is a slow process where very small graphene sheets have been produced so far. The present invention was made to overcome the limitations outlined above.

Thus, reduction of the amount of undesired chemicals (or removal of all these chemicals), reduced processing time, less energy consumption, lower degree of graphene oxidation, drainage of undesired species (eg sulfuric acid) There is an urgent need for graphene production methods that require reduction or elimination of efflux to or in air (eg, SO ₂ and NO ₂ ). This method should allow the production of purer (less oxidation and damage), higher conductivity, larger / wider graphene sheets. In addition, foam structures should be able to be easily manufactured from these graphene sheets.

  Our recent work has provided a chemical-free method of producing isolated nanographene platelets that is novel in that it does not follow the established method of producing nanographene platelets outlined above . Furthermore, this method is highly useful in that it is cost effective and provides novel graphene materials with significantly less environmental impact. Furthermore, as disclosed herein, we combined the chemical free preparation of graphene with the formation of graphene-carbon hybrid forms in one operation.

  For the purpose of defining the claims of the present application, NGP or graphene materials can be single-layer and multi-layer (typically less than 10 layers) pure graphene, graphene oxide, reduced graphene oxide (RGO), graphene fluoride , Discrete sheets / platelets of graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, doped (eg, B or N doped) graphene. Pure graphene has substantially 0% oxygen. RGO typically has an oxygen content of 0.001% to 5% by weight. Graphene oxide (including RGO) can have 0.001 wt% to 50 wt% oxygen. All graphene materials except pure graphene have 0.001 wt% to 50 wt% non-carbon elements (e.g. O, H, N, B, F, Cl, Br, I, etc.). These materials are referred to herein as impure graphene materials. Graphene-carbon foams according to the invention may comprise pure graphene or impure graphene, which enables this versatility by the method according to the invention.

Review on the Production of Graphene Foam Generally speaking, the foam or foam material is composed of pores (or cells) and pore walls (solid material). The pores can be interconnected to form an open cell foam. Graphene foams are composed of pores and pore walls comprising graphene material. There are three main methods of producing graphene foam:

  The first method is typically sealing the graphene oxide (GO) aqueous suspension in a high pressure autoclave, and the GO suspension under high pressure (tens or tens of atmosphere), typically 180 Heating at a temperature in the range of -300 <0> C for an extended period of time (typically 12 to 36 hours). Useful references for this method are: Xu, et al. “Self-Assembled Graphene Hydrogel via a One-Step Hydrothermal Process,” ACS Nano 2010, 4, 4324-4330. There are several major problems associated with this method: (a) the need for high pressure makes it impractical for industrial scale production. As an example, this method can not be performed on a continuous basis. (B) It is difficult, if not impossible, to control the pore size and porosity levels of the resulting porous structure. (C) There is no freedom in changing the shape and size of the resulting reduced graphene oxide (RGO) material (eg, can not be produced in film form). (D) This method involves the use of very low concentrations of GO (eg 2 mg / mL = 2 g / L = 2 kg / kL) suspended in water. Removal of non-carbon elements (up to 50%) can produce less than 2 kg of graphene material (RGO) per 1000 liters of suspension. Furthermore, it is virtually impossible to operate a 1000 liter reactor which needs to withstand high temperature and high pressure conditions. Clearly, this is not an adaptable method for mass production of porous graphene structures.

  The second method is based on a template assisted catalytic CVD method, which comprises CVD deposition of graphene on a sacrificial template (eg Ni foam). The graphene material conforms to the shape and dimensions of the Ni foam structure. The Ni foam is then etched away using an etchant, leaving a monolith of graphene framework that is essentially an open cell foam. Useful references for this method can be found in Zongping Chen, et al. “Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapor deposition,” Nature Materials, 10 (June 2011) 424-428. There are several problems associated with such methods: (a) Catalytic CVD is inherently very slow, consumes very large amounts of energy, and is an expensive method; (b) etchants It is typically a highly undesirable chemical, and the resulting Ni-containing etching solution is a source of contamination. It is very difficult and expensive to recover and reuse the dissolved Ni metal from the etchant solution. (C) When the Ni foam is etched away, it is difficult to maintain the shape and size of the graphene foam without damaging the cell walls. The resulting graphene foam is typically very fragile and fragile. (D) Because the CVD precursor gas may not reach a specific location inside the sacrificial metal foam, it may be difficult to move the CVD precursor gas (eg, hydrocarbon) into the metal foam. Uneven structures may be obtained.

  A third method of making graphene foam also uses a sacrificial material (e.g., colloidal polystyrene particles, PS) onto which the graphene oxide sheet is coated using a self-assembly method. For example, Choi et al. Produced free-standing PS / CMG films by vacuum filtration of a mixed aqueous colloidal suspension of CMG and PS (2.0 μm PS spheres), followed by removal of PS beads to give a 3D macro. Chemically modified graphene (CMG) paper was made in two steps with pore formation [B. G. Choi, et al. “3D Macroporous Graphene Frameworks with High Energy and Power Densities,” ACS Nano, 6 (2012) 4020-4028]. Starting from separately preparing negatively charged CMG colloids and positively charged PS suspensions, Choi et al. Produced ordered free standing PS / CMG paper by filtration. A mixture of CMG colloid and PS suspension is controlled pH (the zeta potential value of the two compounds has the same surface charge (+ 13 ± 2.4 mV for CMG, + 68 ± 5.6 mV for PS)) = 2) dispersed in the solution below. When the pH rises to 6, CMG (Zeta potential = -29 ± 3.7 mV) and PS spheres (Zeta potential = + 51 ± 2.5 mV) assemble due to electrostatic interaction and hydrophobicity between them Then, they were integrated by filtration process into PS / CMG composite paper. This method also has some drawbacks: (a) This method requires very time-consuming chemical treatment of both graphene oxide and PS particles. (B) Removal of PS by toluene also causes weakening of the macroporous structure. (C) Toluene is a very regulated chemical and needs special care. (D) The pore size is typically very large (e.g. several micrometers) and too large for many useful applications.

  The above discussion clearly shows that all prior art methods or processes for producing graphene foam have major deficiencies. Thus, the object of the present invention is a cost-effective method for mass-producing highly conductive, mechanically robust graphene-based foams, in particular, integrated 3D graphene-carbon hybrid foams. It is to provide. This method does not involve the use of chemicals that are not environmentally friendly. This method allows for design control with a high degree of freedom in porosity level and pore size.

  Another object of the present invention is to provide a method for producing a graphene-carbon hybrid foam exhibiting thermal conductivity, conductivity, elastic modulus and / or strength equal to or higher than conventional graphite or carbon foam. .

  Yet another object of the present invention is (a) pure graphene based hybrid foam comprising substantially all carbon only, preferably with mesoscale pore size range (2 to 50 nm); (b) a wide variety Impure graphene foam containing at least 0.001 wt% (typically 0.01 wt% to 25 wt%, most typically 0.1% to 20%) of non-carbon elements that can be used for the application (Graphene fluoride, graphene chloride, nitrogenated graphene and the like).

  Another object of the invention is to provide products (e.g. devices) comprising the graphene-carbon foams of the invention, and methods of operating these products.

The present invention provides a method of directly producing integrated 3D graphene-carbon hybrid foams from particles of graphite material and particles of polymer. This method is surprisingly simple. This method is:
(A) mixing the plurality of particles of the graphite material and the plurality of particles of the solid polymer support material in a collision chamber of the energy collision apparatus to form a mixture;
(B) Stripping the graphene sheet from the graphite material and moving the graphene sheet to the surface of the solid polymer carrier material particles to form graphene-coated polymer particles or graphene-embedded polymer particles within the collision chamber for a sufficient amount of time Operating the energy collision device with a certain frequency and a certain intensity (for example, the collision device applies kinetic energy to the polymer particles during operation, and then the polymer particles collide with the graphite particle surface / edge, Graphene sheets are exfoliated from the impacted graphite particles, and these exfoliated graphene sheets adhere to the surface of these polymer particles, which is referred to herein as the "direct transfer" process, and any third factor Graphene sheet directly from the graphite particle to the surface of the polymer particle without Means that the motion);
(C) recovering the graphene-coated polymer particles or the graphene-embedded polymer particles from the collision chamber to solidify the graphene-coated polymer particles or the graphene-embedded polymer particles into a desired shape of the graphene-polymer hybrid structure (this solidification step , May be as simple as a consolidation step of simply loading the graphene coated particles or graphene embedded particles into the desired shape);
(D) Pyrolyze this shape of the graphene-polymer hybrid structure and thermally convert the polymer to carbon or graphite that combines the pores with the graphene sheet to form an integrated 3D graphene-carbon hybrid foam And step.

  In certain alternative embodiments, a plurality of collision balls or media are added to the collision chamber of the energy collision device. These collision balls are accelerated by the collision device to collide with the surface / edge of the graphite particles and exfoliate the graphene sheet from them. These graphene sheets move temporarily to the surface of these collision balls. The collision balls supporting these graphenes subsequently collide with the polymer particles, and the supported graphene sheets move to the surface of these polymer particles. This series of events is referred to herein as "indirect movement". In some embodiments of the indirect transfer process, step (c) comprises manipulating the magnet to separate the collision ball or medium from the graphene coated polymer particles or the graphene embedded polymer particles.

  The solid polymer material particles can comprise plastic or rubber beads, pellets, spheres, wires, fibers, filaments, disks, ribbons, or rods having a diameter or thickness of 10 nm to 10 mm. Preferably, the diameter or thickness is 100 nm to 1 mm, more preferably 200 nm to 200 μm. The solid polymer can be selected from solid particles of thermoplastics, thermosetting resins, rubbers, semi-penetrating network polymers, penetrating network polymers, natural polymers, or combinations thereof. In one embodiment, prior to step (d), the solid polymer is partially removed by melting, etching or dissolution in a solvent.

  In certain embodiments, the graphite material is natural graphite, synthetic graphite, highly oriented pyrolytic graphite, graphite fibers, graphite nanofibers, fluorinated graphite, graphite oxide, chemically modified graphite, exfoliated graphite, exfoliated recompressed graphite, It is selected from expanded graphite, mesocarbon microbeads, or a combination thereof. Preferably, the graphite material comprises a non-intercalated and non-oxidized graphite material which has not been previously subjected to a chemical treatment or oxidation treatment prior to the mixing step (a).

  The inventors have surprisingly identified that a wide variety of collision devices can be used to practice the present invention. For example, energy collision devices include vibration ball mills, planetary ball mills, high energy mills, basket mills, agitator ball mills, cryo ball mills, micro ball mills, tumbler ball mills, continuous ball mills, stirred ball mills, pressure ball mills, freezer mills, vibratory sieves, bead mills, It may be a nanobeads mill, an ultrasonic homogenizer mill, a centrifugal planetary mixer, a vacuum ball mill, or a resonance acoustic mixer.

  Polymer particles having a high carbon yield or carbon yield (e.g.,> 30 wt%) can be selected to form the carbon component of the resulting graphene-carbon hybrid foam. Carbon yield is the weight percent value of a polymer structure that is converted by heat to a solid carbon phase instead of being a volatile gas fraction. High carbon yield polymers include phenolic resins, polyfurfuryl alcohol, polyacrylonitrile, polyimides, polyamides, polyoxadiazoles, polybenzoxazoles, polybenzobisoxazoles, polythiazoles, polybenzothiazoles, polybenzobisthiazoles, poly (p -Phenylenevinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof.

  If less carbon content (higher graphene ratio) is desired in the graphene-carbon hybrid foam, the polymer may be polyethylene, polypropylene, polybutylene, polyvinyl chloride, polycarbonate, acrylonitrile-butadiene (ABS), polyester, polyvinyl Alcohol, poly vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene oxide (PPO), polymethyl methacrylate (PMMA), their copolymers, their polymer blends, or combinations thereof It can include low carbon yield polymers of choice.

  These polymers (both high and low carbon yields) are converted to carbon materials when heated to temperatures of 300 to 2,500 ° C., which preferentially nucleate near the edge of the graphene sheet Please note that. Such carbon materials serve to fill the gaps between the graphene sheets to form interconnected electron conduction paths. In other words, the resulting graphene-carbon hybrid foam is composed of an integrated 3D network of carbon-bonded graphene sheets, thereby causing uninterrupted electrons and phonons between the graphene sheets or regions (quantized lattice Continuous transport of vibration). Further heating to temperatures above 2,500 ° C. may graphitize the carbon phase to which the graphene is attached if the carbon phase is “soft carbon” or is graphitizable. In such situations, both conductivity and thermal conductivity are further increased.

  Thus, in certain embodiments, the pyrolysis step comprises carbonizing the polymer at a temperature of 200 ° C. to 2,500 ° C. to obtain a carbon bonded graphene sheet. Optionally, the carbon bonded graphene sheets can then be graphitized at a temperature of 2,500 ° C. to 3,200 ° C. to obtain graphite bonded graphene sheets.

It should be noted that the pyrolysis of the polymer tends to form pores in the resulting polymer carbon layer, as volatile gas molecules such as CO ₂ and H ₂ O are generated. However, such pores are also more prone to collapse if not suppressed as the polymer carbonizes. Surprisingly, we have found that graphene sheets that wrap polymer particles can inhibit shrinkage and collapse of carbon pore walls, and some carbon species also penetrate into the gaps between graphene sheets It has been discovered that these carbon species bond graphene sheets together. The pore size and pore volume (porosity level) of the resulting 3D-integrated graphene foam is determined by the size of the starting polymer and the carbon yield of the polymer and to a lesser extent by the thermal decomposition temperature Ru.

  In certain preferred embodiments, the solidifying step comprises compacting the material of these graphene coated polymer particles into a desired shape. For example, a compacted green body can be easily formed by squeezing and compacting the material of the graphene coated particles into the mold cavity. When the polymer is rapidly heated and melted and the green body is slightly compressed, the heat can cause the polymer particles to fuse slightly together, and can be rapidly cooled to solidify the body. The solidified body is then subjected to a pyrolysis treatment (carbonization of the polymer and optionally graphitization).

  In some further embodiments, the solidifying step comprises melting the polymer particles to form a polymer melt mixture having graphene sheets dispersed therein, forming the desired shape from the polymer melt mixture, and Solidifying the shape into a graphene-polymer composite structure. Such shapes may be rods, films (thin or thick film, wide or narrow, single sheet or roll form), fibers (short filaments or continuous long filaments), plates, ingots, any regular shape, or It may be irregular in shape. This graphene-polymer composite shape is then subjected to thermal decomposition

  Alternatively, the solidifying step may include dissolving the polymer particles in a solvent to form a polymer solution mixture in which the graphene sheet is dispersed, forming the desired shape from the polymer solution mixture, and removing the solvent. Solidifying the shape to obtain a graphene-polymer composite structure. The composite structure is then pyrolyzed to form a porous structure.

  The solidifying step includes melting the polymer particles to form a polymer melt mixture in which the graphene sheet is dispersed, extruding the mixture into a rod form or sheet form, spinning the mixture into fiber form And spraying the mixture into a powder form or casting the mixture into an ingot form.

  In some embodiments, the solidifying step comprises dissolving the polymer particles in a solvent to form a polymer solution mixture having graphene sheets dispersed therein, and extruding the solution mixture to form a rod or sheet form Including spinning the solution mixture into fiber form, spraying the solution mixture into powder form, or casting the solution mixture into ingot form and removing the solvent. .

  In one particular embodiment, the polymer solution mixture is sprayed to form a graphene-polymer composite coating or film, which is then subjected to its thermal decomposition (carbonization or carbonization and graphitization).

  Preferably, the solidifying step may comprise compacting the graphene coated polymer particles into a porous green compact with macropores, then petroleum pitch, coal tar pitch, aromatic organic materials such as naphthalene Alternatively, the pores can be impregnated or impregnated with additional carbon source material selected from other derivatives of pitch), monomers, organic polymers, or combinations thereof. Organic polymers include phenolic resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polybenzothiazole, polybenzobisthiazole, poly (p-phenylenevinylene) ), Polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof may comprise high carbon yield polymers. These thermal species provide an additional source of carbon when thermal decomposition of the green compact of the infiltrated graphene-coated polymer particles is performed when higher amounts of carbon are desired in the hybrid foam.

The present invention is an integrated 3D graphene-carbon hybrid foam composed of a plurality of pores and pore walls, wherein the pore walls have a carbon material to graphene weight ratio of 1/200 to 1/2. 2 to 10 layers of laminated graphene comprising a monolayer or few-layer graphene sheet chemically bonded by a carbon material, the few-layer graphene sheet having a spacing d _{002 of} 0.3354 nm to 0.36 nm, measured by X-ray diffraction Plane, a single or few layer graphene sheet is pure graphene material with substantially 0% non-carbon elements, or 0.001 wt% to 35 wt% (preferably 0.01% to 25%) Containing impure graphene materials having non-carbon elements), impure graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, bromide graph Also provided is an integrated 3D graphene-carbon hybrid foam selected from: enene, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, or a combination thereof. The plurality of monolayer or multi-layer graphenes surrounding the underlying polymer particles can overlap one another to form a stack of graphene sheets. This stack can have a thickness of more than 5 nm, in some cases more than 10 nm, or even more than 100 nm.

The integral 3D graphene-carbon hybrid foam typically has a density of 0.001 to 1.7 g / cm ³ and a specific surface area of 50 to 3,000 m ² / g. In a preferred embodiment, the pore wall comprises laminated graphene planes having an interplanar spacing d _{002 of} 0.3354 nm to 0.40 nm as measured by X-ray diffraction.

  For oil recovery applications (eg separation of oil from water), graphene-carbon preferably has an oxygen content of 1% to 25% by weight (more preferably 1 to 15%, most preferably 1 to 10%) Have. This is done when the starting material is graphite oxide or at a temperature of 300-1,500 ° C. (preferably less than 1,000 ° C.) in an environment where the carbonization process is slightly oxidizing, followed by graphitization. It can be realized if not The inventors have surprisingly found that highly porous graphene-carbon foams of this nature can absorb oil from oil-water mixtures up to 500% of their own weight.

  For temperature control applications, graphene-carbon hybrid foams are preferably produced by graphitizing the carbon-bonded graphene sheets (after carbonization) under compressive stress. This promotes orientation and reorganization (coalescence, growth, etc.) of the graphene sheets or graphene regions. As a result, the sheet or film of graphene-carbon foam exhibits a thermal conductivity of at least 200 W / mK per unit specific gravity, and / or a conductivity of 2,000 S / cm or higher per unit specific gravity.

In one embodiment, the pore walls comprise pure graphene and the 3D solid graphene-carbon foam has a density of 0.001 to 1.7 g / cm ³ or an average pore size of 2 to 50 nm. In one embodiment, the pore walls are from graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, and combinations thereof Wherein the solid graphene foam comprises a non-carbon element content in the range of 0.01 wt% to 20 wt%. In other words, the non-carbon element can include an element selected from oxygen, fluorine, chlorine, bromine, iodine, nitrogen, hydrogen or boron. In a particular embodiment, the pore walls comprise graphene fluoride and the solid graphene foam comprises a fluorine content of 0.01 wt% to 20 wt%. In another embodiment, the pore wall comprises graphene oxide and the solid graphene foam comprises an oxygen content of 0.01 wt% to 20 wt%. In one embodiment, the solid graphene-carbon hybrid foam has a specific surface area of 200 to 2,000 m ² / g or a density of 0.01 to 1.5 g / cm ³ .

  It should be noted that there is no limitation on the shape or size of the graphene-carbon hybrid foam according to the present invention. In a preferred embodiment, from solid graphene-carbon hybrid foam, a thickness of 100 nm or more and 10 cm or less and a length of at least 1 meter, preferably at least 2 meters, more preferably at least 10 meters, most preferably at least 100 meters A roll sheet form of continuous length (roll of continuous foam sheet) having a length of This sheet roll is manufactured by a roll-to-roll process. There is no prior art graphene based foam formed in sheet roll form. It has not previously been found or suggested that it is possible to have a roll-to-roll process to produce either pure or impure graphene foams in continuous length.

  For thermal management or conductive based applications, the graphene-carbon foam preferably has an oxygen content or non-carbon content of less than 1% by weight, and the pore walls have graphene spacings less than 0.35 nm, units It has a laminated graphene surface having a thermal conductivity of at least 250 W / mK per specific gravity, and / or a conductivity of 2,500 S / cm or higher per unit specific gravity.

  In a further preferred embodiment, the graphene-carbon hybrid foam has an oxygen content or non-carbon content of less than 0.01% by weight, the pore walls have a graphene spacing less than 0.34 nm, unit specific gravity It comprises a laminated graphene surface having a thermal conductivity of at least 300 W / mK and / or a conductivity of 3,000 S / cm or more per unit specific gravity.

  In yet another preferred embodiment, the graphene-carbon hybrid foam has an oxygen content or non-carbon content of 0.01 wt% or less, and the pore walls have a graphene spacing less than 0.336 nm, It includes laminated graphene surfaces having mosaic spread values of 0.7 or less, thermal conductivity of at least 350 W / mK per unit specific gravity, and / or conductivity of 3,500 S / cm or more per unit specific gravity.

  In yet another preferred embodiment, the graphene foam has a graphene spacing of less than 0.336 nm, a mosaic spread value of 0.4 or less, a thermal conductivity of more than 400 W / mK per unit specific gravity, and / or 4 per unit specific gravity It has a pore wall including a laminated graphene surface having a conductivity of over 1,000 S / cm.

  In a preferred embodiment, the pore wall comprises laminated graphene planes having graphene spacings less than 0.337 nm and mosaic spread values less than 1.0. In a preferred embodiment, the graphene foam exhibits a degree of graphitization of 80% or more (preferably 90% or more), and / or a mosaic spread value of less than 0.4. In a preferred embodiment, the pore wall comprises a 3D network of interconnected graphene planes.

  In a preferred embodiment, the solid graphene-carbon hybrid foam comprises mesoscale pores having a pore size of 2 nm to 50 nm. Solid graphene foams can also be made to include micron-scale pores (1-500 μm).

  The invention also provides an oil removal device or oil separation device comprising the 3D graphene-carbon hybrid foam according to the invention as an oil absorbing element. Also provided is a solvent removal or separation device comprising the 3D graphene-carbon hybrid foam as a solvent absorbing element.

  The invention also provides a method of separating oil from an oil-water mixture (e.g. water from which the oil has drained, or wastewater from the oil sands). The method comprises the steps of (a) providing an oil absorbing element comprising an integrated graphene-carbon hybrid foam, and (b) contacting an oil-water mixture with the element to absorb oil from the mixture into the element. And (c) removing the component from the mixture and extracting oil from the component. Preferably, the method comprises the further step (d) of recycling said element.

  Furthermore, the invention provides a method of separating an organic solvent from a solvent-water mixture or from a mixture of solvents. The method comprises the steps of (a) providing an organic solvent absorbing element comprising an integrated graphene-carbon hybrid foam, and (b) the element being an organic solvent-water mixture, or a first solvent and at least a second solvent. Contacting with a mixture of solvents including the solvent, (c) allowing the element to absorb the organic solvent from the mixture, or absorbing the first solvent from at least the second solvent, and (d) above. Removing the element from the mixture and extracting the organic solvent or the first solvent from the element. Preferably, the method comprises the further step (e) of recycling the element.

Figure 2 is a flow chart showing the most commonly used prior art method of producing highly oxidized NGP with time consuming chemical oxidation / intercalation, cleaning, and high temperature exfoliation procedures. 1 is a flow chart showing a method according to the invention for producing an integrated 3D graphene-carbon hybrid foam. FIG. 2 is a schematic diagram of a thermally induced conversion of polymer to carbon whereby graphene sheets are bonded together to form a 3D graphene-carbon hybrid foam. The consolidated structure of the graphene coated polymer particles is converted to a highly porous structure. It is a SEM image of the internal structure of 3D graphene-carbon hybrid foam. FIG. 6 is a SEM image of the internal structure of another 3D graphene-carbon hybrid foam. FIG. 7 is the thermal conductivity values versus specific gravity of 3D integrated graphene-carbon foam, mesophase pitch-derived graphite foam, and Ni foam template-assisted CVD graphene foam produced by the method according to the present invention. FIG. 7 is the thermal conductivity value of 3D graphene-carbon foam and hydrothermally reduced GO graphene foam. FIG. 7 is the thermal conductivity value of 3D graphene-carbon hybrid foam and pure graphene foam (made by adding blowing agent and casting followed by heat treatment) plotted as a function of final (maximum) heat treatment temperature. FIG. 10 is conductivity values of 3D graphene-carbon foam and hydrothermally reduced GO graphene foam. The amount of oil absorbed per gram of integrated 3D graphene-carbon hybrid foam plotted as a function of oxygen content in the foam having a porosity level of about 98% (oil from oil-water mixture Separation). The amount of oil absorbed per gram of integrated 3D graphene-carbon hybrid foam plotted as a function of porosity level (for the same oxygen content). The amount of chloroform absorbed from a chloroform-water mixture plotted as a function of degree of fluorination. FIG. 2 is a schematic view of a heat sink structure (two examples).

  The present invention provides a method of directly producing integrated 3D graphene-carbon hybrid foams from particles of graphite material and particles of polymer.

  As schematically shown in FIG. 2 (A), the method starts with mixing a plurality of particles of graphite material and a plurality of particles of solid polymer carrier material to form a mixture, the mixture Energy collision devices (eg, vibration ball mill, planetary ball mill, high energy mill, basket mill, agitator ball mill, cryo ball mill, micro ball mill, tumbler ball mill, continuous ball mill, stirred ball mill, pressure ball mill, freezer mill, vibratory sieve, bead mill , Nanobeads Mill, Ultrasonic Homogenizer Mill, Centrifuge Planetary Mixer, Vacuum Ball Mill, or Resonant Acoustic Mixer) in a collision chamber. During operation, the energy collision device can impart kinetic energy to solid particles contained therein to cause polymer particles to collide on graphite particles with high strength and frequency.

  Under typical operating conditions, such collision events cause the graphene sheets to delaminate from the graphite material and transfer them to the surface of the solid polymer carrier particles. These graphene sheets wrap around the polymer particles to form graphene coated polymer particles or graphene embedded polymer particles inside the collision chamber. This is referred to herein as the "direct transfer" process, which means that the graphene sheet moves directly from the graphite particles to the surface of the polymer particles without mediating any third factor.

  Alternatively, multiple collision balls or media can be added to the collision chamber of the energy collision device. These collision balls accelerated by the collision device collide with the surface / edge of the graphite particles with high kinetic energy at an angle that is favorable for peeling the graphene sheet from the graphite particles. These graphene sheets move temporarily to the surface of these collision balls. The collision balls supporting these graphenes subsequently collide with the polymer particles, and the supported graphene sheets move to the surface of these polymer particles. This series of events is referred to herein as the "indirect transfer" process. These events occur very frequently, so most polymer particles are typically covered with graphene sheets in less than one hour. In some embodiments of the indirect transfer process, step (c) comprises manipulating the magnet to separate the impacting ball or medium from the graphene coated polymer particles or graphene embedded polymer particles.

  The method then includes recovering the graphene coated polymer particles or graphene embedded polymer particles from the collision chamber, and solidifying the graphene coated polymer particles or graphene embedded polymer particles into the desired shape of the graphene-polymer composite structure . This solidification step may be as simple as a consolidation step which simply mechanically fills the graphene coated particles or graphene embedded particles into the desired shape. Alternatively, the solidifying step may involve melting the polymer particles to form a polymer matrix having graphene sheets dispersed therein. Such graphene-polymer structures may be of any practical shape or size (fibers, rods, plates, cylinders, or any regular shape or irregular shape).

  As shown in FIGS. 3 (A) and 3 (B), the graphene-polymer compact or composite structure is then pyrolyzed to thermally convert the polymer to carbon or graphite that bonds to the graphene sheet, An integrated 3D graphene-carbon hybrid foam is formed.

  Polymer particles with high carbon or carbon yield (eg,> 30% by weight of the polymer become part of the volatile gas) to form the carbon component of the resulting graphene-carbon hybrid foam Alternatively, it can be selected to be converted to a solid carbon phase. High carbon yield polymers include phenolic resins, polyfurfuryl alcohol, polyacrylonitrile, polyimides, polyamides, polyoxadiazoles, polybenzoxazoles, polybenzobisoxazoles, polythiazoles, polybenzothiazoles, polybenzobisthiazoles, poly (p -Phenylenevinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof. When pyrolyzed, the particles of these polymers become porous as shown in the lower part of FIG. 2 (B).

  If lower carbon content (higher graphene to carbon ratio) and lower foam density are desired for graphene-carbon hybrid foam, the polymer may be polyethylene, polypropylene, polybutylene, polyvinyl chloride, polycarbonate, acrylonitrile -Butadiene (ABS), polyester, polyvinyl alcohol, poly vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene oxide (PPO), polymethyl methacrylate (PMMA), their copolymers, they Low carbon yield polymers selected from polymer blends of the foregoing, or combinations thereof. When pyrolyzed, the particles of these polymers become porous as shown in the central portion of FIG. 2 (B).

  These polymers (both high and low carbon yields) are converted to carbon materials when heated at temperatures of 300 to 2,500 ° C., which preferentially nucleate near the edge of the graphene sheet Do. Such carbon materials naturally fill the gaps between the graphene sheets to form interconnected electron conduction pathways. In fact, the resulting graphene-carbon hybrid foam is composed of an integrated 3D network of carbon-bonded graphene sheets, which allows the electrons and phonons (quantization between graphene sheets or regions without interruption) Continuous transport of lattice vibration). Further heating to temperatures above 2,500 ° C. can graphitize the carbon phase and further increase both conductivity and thermal conductivity. If the graphitization time exceeds one hour, the amount of non-carbon elements also typically decreases to less than 1% by weight.

It should be noted that the organic polymer typically contains significant amounts of non-carbon elements, which can be reduced or eliminated by heat treatment. Thus, pyrolysis of the polymer results in the formation and generation of volatile gas molecules such as CO ₂ and H ₂ O, which results in the formation of pores in the resulting polymer carbon phase. However, such pores are also more prone to collapse if unrestrained when the polymer is carbonized (the carbon structure may shrink when non-carbon elements are released). The present inventors have surprisingly found that graphene sheets that wrap polymer particles can suppress the collapse of carbon pore walls. On the other hand, some carbon species also penetrate into the interstices between the graphene sheets, where these carbon species bond the graphene sheets together. The pore size and pore volume (porosity level) of the resulting 3D-integrated graphene foam is mainly determined by the size of the starting polymer and the carbon yield of the polymer.

Graphite materials as a supply source of graphene sheets include natural graphite, synthetic graphite, highly oriented pyrolytic graphite, graphite fibers, graphite nanofibers, fluorinated graphite, graphite oxide, chemically modified graphite, exfoliated graphite, exfoliated and recompressed graphite , Expanded graphite, mesocarbon microbeads, or a combination thereof. In this regard, there are several additional surprising elements associated with the method according to the invention:
(1) Peeling graphene sheets from natural graphite by using polymer particles alone, without using heavier and harder collision balls (such as, for example, zirconium dioxide or steel balls commonly used in ball mills) can do. The exfoliated graphene sheet moves directly to the surface of the polymer particle and tightly wraps the polymer particle.
(2) It is also surprising that it is possible to exfoliate the graphene sheet from artificial graphite such as mesocarbon microbeads (MCMB), which are known to have a skin layer of amorphous carbon, by impacting polymer particles.
(3) By using a harder collision ball, the graphene-like surface of carbon atoms constituting the internal structure of carbon or graphite fiber can also be exfoliated and transferred to the surface of the polymer particle. Such a thing is not taught or suggested in the prior art.
(4) The present invention is very simple, fast, scaleable, environmentally friendly, costing that virtually all the drawbacks associated with the prior art graphene sheet manufacturing methods are avoided Provide a highly effective method. The graphene sheets are immediately transferred to the polymer particles to encapsulate the polymer particles, which are then easily converted to integral 3D graphene-carbon hybrid foams.

  If the starting graphite is purposely oxidized to a certain extent (eg containing 2 to 15% by weight of oxygen), imparting a desired desired degree of hydrophilicity to the pore walls of the graphene-carbon hybrid foam Note that you can. Alternatively, the oxygen containing functional group can be attached to the carbon phase when the carbonization process is performed in a slightly oxidizing environment. These characteristics make it possible to separate the oil from the water by selectively absorbing the oil from the oil-water mixture. In other words, such graphene-carbon hybrid foam materials allow for the recovery of oil from water, facilitating the cleaning of the river, lake, or sea from which the oil has spilled. Oil absorption capacity is typically 50% to 500% of the foam's own weight. This is a surprisingly useful material for environmental protection purposes.

  If high conductivity or thermal conductivity is desired, the graphite material should be selected from non-intercalated, non-oxidized graphite materials that have not been previously chemically or oxidized prior to entering the collision chamber. it can. Alternatively, or additionally, the graphene-carbon foam can be graphitized at temperatures greater than 2,500 ° C. The resulting material is particularly useful for thermal management applications (eg, for use in making finned heat sinks, heat exchangers, or heat spreaders).

  It should be noted that the graphene-carbon foam can be compressed during and / or after the graphitization process. This operation enables adjustment of the orientation and porosity of the graphene sheet.

X-ray diffraction patterns were obtained using an X-ray diffractometer equipped with CuKcv radiation. Diffraction peak shifts and broadening were calibrated using silicon powder standards. The degree of graphitization g is X-ray using Mering's equation d ₀₀₂ = 0.3354 g + 0.344 (1-g) (wherein, d ₀₀₂ is the layer spacing in nm of graphite or graphene crystal) Calculated from the pattern. This equation is valid only when d ₀₀₂ is about 0.3440 nm or less. Graphene foam walls with d ₀₀₂ greater than 0.3440 nm are oxygen or fluorine containing functional groups that function as spacers to increase the graphene spacing (-F, -OH,> O on the surface or edge of the graphene molecular plane , And -COOH etc.).

  Stacked coupled graphene surfaces in graphene foam walls, and another structural indicator that can be used to characterize the degree of order of conventional graphite crystals, is the rocking curve (X-ray diffraction intensity of (002) or (004) reflection Is a "mosaic spread" represented by the full width at half maximum of This degree of order characterizes the crystal size (or grain size) of graphite or graphene, the amount of grain boundaries and other defects, and the degree of preferred grain orientation. An almost perfect single crystal of graphite is characterized by having a mosaic spread value of 0.2 to 0.4. Most of the graphene walls of the present inventors have mosaic spread values within this 0.2-0.4 range (when manufactured at a heat treatment temperature (HTT) of 2,500 ° C. or higher). However, some values are in the range of 0.4 to 0.7 for HTTs between 1,500 and 2,500 ° C and 0 for HTTs between 300 and 1,500 ° C. In the range of 7 to 1.0.

The graphene foam wall of the present invention has several huge graphene planes (length / length) by more detailed studies using a combination of SEM, TEM, limited field diffraction, X-ray diffraction, AFM, Raman spectroscopy and FTIR It is shown that the width is typically composed of >> 20 nm, more typically >> 100 nm, often >> 1 μm, often >> 10 μm, or even >> 100 μm) . When the final heat treatment temperature is less than 2,500 ° C., these large graphene planes are often van der (like conventional graphite microcrystals) along the thickness direction (crystallographic c-axis direction) Not only Waals force but also covalent bond is laminated and bonded. In these cases, without wishing to be limited by theory, Raman and FTIR spectroscopy studies seem to indicate the coexistence of sp ² (dominant) and sp ³ (weak is present) cell configurations However, in graphite, it is only conventional sp ² .

The integrated 3D graphene-carbon hybrid foam of the present invention is composed of a plurality of pores and pore walls, wherein the pore walls are made of a carbon material having a carbon material to graphene weight ratio of 1/100 to 1/2. Chemically bonded single-layer or multi-layer graphene sheets, which have 2 to 10 layers of stacked graphene planes with spacing d _{002 of} 0.3354 nm to 0.36 nm, measured by X-ray diffraction Single-layer or few-layer graphene sheets are pure graphene materials with substantially 0% non-carbon elements, or 0.01% -25% by weight non-carbon elements (more typically <15%) Impure graphene material having impure graphene material), impure graphene material is graphene oxide, reduced graphene oxide, graphene fluoride, It is selected from phen, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, or a combination thereof. The plurality of single-layer or multi-layer graphenes surrounding the underlying polymer particles can overlap one another to form a stack of graphene sheets. The laminate can have a thickness of more than 5 nm, in some cases more than 10 nm, and even more than 100 nm.

The integral 3D graphene-carbon hybrid foam typically has a density of 0.001 to 1.7 g / cm ³ , a specific surface area of 50 to 3,000 m ² / g, at least 200 W / m K per unit specific gravity. It has a thermal conductivity and / or a conductivity of 2,000 S / cm or more. In a preferred embodiment, the pore wall comprises laminated graphene planes having an interplanar spacing d _{002 of} 0.3354 nm to 0.40 nm as measured by X-ray diffraction.

  Many of the graphene sheets of the present invention can be coalesced with one another by covalent bonds into an integrated graphene element. The gaps between the free ends of these non-coalescent sheets or coalesced shorter sheets are bound by the carbon phase converted from the polymer. Their unique chemical composition (including oxygen or fluorine content, etc.), morphology, crystal structure (including graphene spacing), and structural features (eg, orientation angle, several defects, chemical bonds, and graphene sheets) The graphene-carbon hybrid foam according to the present invention has remarkable thermal conductivity, conductivity, mechanical strength, and It has a unique combination of stiffness (modulus of elasticity).

Thermal Management Applications The above features and characteristics make the integrated 3D graphene-carbon hybrid foam an ideal element in a wide variety of engineering and biomedical applications. For example, for thermal management purposes alone, graphene-carbon foam can be used for the following applications:
a) Compressible, high thermal conductivity graphene-carbon hybrid foam is ideal for use as a thermal interface material (TIM) that can be incorporated between a heat source and a heat spreader or between a heat source and a heat sink is there.
b) The hybrid foam can itself be used as a heat spreader due to its high thermal conductivity.
c) The hybrid foam is used as a heat sink or heat dissipating material because of its high heat diffusive capacity (high thermal conductivity) and high heat dissipating capacity (many surface pores where a large amount of air convection micro or nano channels can be obtained) be able to.
d) Light weight (low density adjustable between 0.001 and 1.8 g / cm ³ ), high thermal conductivity per unit specific gravity or per unit physical density, and high structural integrity (graphene sheet is carbon This hybrid foam is an ideal material for durable heat exchangers.

  Thermal management devices or heat dissipation devices based on the graphene-carbon hybrid foams include heat exchangers, heat sinks (eg finned heat sinks), heat pipes, highly conductive inserts, thin or thick conductive plates (between heat sinks and heat sources A thermal interface medium (or thermal interface material TIM), a thermoelectric cooler plate or a Peltier cooler plate, and the like.

  A heat exchanger is a device used to transfer heat between one or more fluids, for example gases and liquids are flowed separately into different channels. Multiple fluids are typically separated by solid walls to prevent mixing. The graphene-carbon hybrid foam material according to the invention is an ideal material for such a wall, provided that the foam does not become a totally open cell foam allowing fluid mixing. The process according to the invention allows the production of both open and closed cell foam structures. High surface pore area allows very rapid exchange of heat between two or more fluids

  Heat exchangers are widely used in refrigeration systems, air conditioners, heaters, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas treatment, and sewage treatment. A well-known example of a heat exchanger can be found in an internal combustion engine, where circulating engine coolant flows through the radiator coil while air flows past the coil, whereby the coolant is cooled And the incoming air is heated. Solid walls (e.g. constituting the radiator coil) are usually made of high thermal conductivity materials such as Cu and Al. Graphene foams according to the present invention, which have either higher thermal conductivity or a wider specific surface area, are excellent alternatives to, for example, Cu and Al.

  Many types of heat exchangers on the market: shell and tube heat exchangers, flat plate heat exchangers, plate and shell heat exchangers, adiabatic wheel heat exchangers, flat plate fin heat exchangers, pillow plate heat exchangers There are fluid heat exchangers, waste heat recovery devices, dynamic scraped surface heat exchangers, phase change heat exchangers, direct contact heat exchangers, and microchannel heat exchangers. Any of these types of heat exchangers can take advantage of the very high thermal conductivity and very large specific surface area of the foam material according to the invention.

  The solid graphene foam according to the invention can also be used in a heat sink. Heat sinks are widely used in electronic devices for the purpose of heat dissipation. Central processing units (CPUs) and batteries in portable microelectronic devices (such as notebook computers, tablets, and smartphones) are well known heat sources. Typically, when a metal or graphite body (e.g. Cu foil or graphite foil) is brought into contact with a high temperature surface, this body promotes the dissipation of heat to the external surface or to the outside air (mainly by conduction and convection) To a lesser extent by radiation). In most cases, a thin thermal interface material (TIM) is interposed between the high temperature surface of the heat source and the heat dissipating surface of the heat spreader or heat sink.

  Heat sinks usually have one or more flat surfaces to ensure good thermal contact with the parts to be cooled, and combs or fins to increase the surface contact with air and thereby increase the heat release rate A highly conductive material structure having an array of lobes. The heat sink can be used with a fan to increase the airflow rate on the heat sink. The heat sink can have a plurality of fins (wide or protruding surfaces) to improve heat transfer. In electronic devices with a limited amount of space, it is necessary to optimize the fin shape / arrangement to maximize the heat transfer density. Alternatively or additionally, cavities (inverted fins) can be incorporated in the area formed between adjacent fins. These cavities are effective for extracting heat from the various heating elements to the heat sink.

  Typically, the integrated heat sink comprises a heat collecting member (core or base) and at least one heat dissipating member (eg one fin or plurality of heat sinking members together with the heat collecting member (base) to form a finned heat sink And the fin). The fins and core are inherently connected or integrated into an integrated body without the use of externally applied adhesives or mechanical fastening means for connecting the fins to the core. The heat collection base has a surface in thermal contact with a heat source (e.g., an LED) to collect heat from the heat source and dissipate the heat into the air through the fins.

  As an illustrative example, FIG. 10 shows a schematic view of two heat sinks 300 and 302. The first includes a heat collecting member (or base member) 304 and a plurality of fins or heat dissipating members (eg, fins 306) connected to the base member 304. Base member 304 is shown to have a heat collecting surface 314 intended to be in thermal contact with the heat source. The heat dissipating member or fin 306 is shown to have at least one heat dissipating surface 320.

  One particularly useful embodiment is: (a) a base 308 including a heat collecting surface 318; (b) a plurality of spaced apart parallel planes supported by or integral with the base 308. A radial finned heat sink assembly comprising a radial finned heat sink assembly including fin-like fin members (e.g. two examples 310, 312), the planar fin member (e.g. 310) comprising at least one heat dissipating surface 322; The plurality of parallel planar fin members are preferably equally spaced.

  The graphene-carbon hybrid foam according to the invention, which is highly elastic and resilient, is itself a good thermal interface material and also a very effective thermal diffusion element. Furthermore, the high conductivity foam can also be used as an insert for cooling the electronics and for improving the heat removal from the small chip to the heat sink. Because the space presented by the high conductivity material is a major issue, it is a more effective design to take advantage of the high conductivity pathways that can be incorporated into the heating element. The elastic and highly conductive solid graphene foam disclosed herein fully meets these requirements.

  Due to high elasticity and high thermal conductivity, the solid graphene-carbon hybrid foam according to the invention is arranged as a heat transfer interface between a heat source and a low temperature flowing fluid (or any other heat sink) to improve the cooling performance Be a good conductive board. In such an arrangement, the heat source is cooled under a thick graphene foam plate instead of being cooled in direct contact with the cooling fluid. Graphene foam planks can significantly improve heat transfer between the heat source and the cooling fluid in order to conduct heat flow in an optimal manner. No additional pumping capacity and no additional heat transfer surface area is required.

  The solid graphene foam is also an excellent material for constructing heat pipes. A heat pipe is a heat transfer device that uses a two phase working fluid or refrigerant to transport large amounts of heat with very small temperature differentials between hot and cold interfaces. A conventional heat pipe consists of a sealed hollow tube made of a thermally conductive metal such as Cu or Al, and a wick which returns the working fluid from the evaporator to the condenser. This pipe contains saturated liquid and vapor of the working fluid (water, methanol or ammonia) and any other gases are excluded. However, both Cu and Al are susceptible to oxidation or corrosion, so their performance declines relatively quickly with time. In contrast, the solid graphene foams of the present invention are chemically inert and there are no problems with their oxidation or corrosion. Heat pipes for temperature control of electronics can have solid graphene foam envelopes and wicks, and water as the working fluid. Graphene / methanol can be used if the heat pipe needs to operate below the freezing point of water, or a graphene / ammonia heat pipe can be used to cool the electronics through the gap.

  The Peltier cold plate operates by the Peltier effect where heat flux is generated between the junctions of two different conductors by applying an electric current. This effect is commonly used to cool electronic components and small devices. In practice, many such junctions can be arranged in series to increase the effectiveness to the amount of heating or cooling required. The solid graphene foam can be used to improve heat transfer efficiency.

Filtration and Fluid Absorption Applications The solid graphene foams of the present invention can be made to include fine pores (<2 nm) or mesoscale pores with pore sizes of 2 nm to 50 nm. The solid graphene-carbon hybrid foam of the present invention can also be manufactured to include micron-scale pores (1 to 500 μm). Based solely on well-controlled pore sizes, the graphene-carbon foams of the present invention can be excellent filter materials for air or water filtration.

  Furthermore, the chemistry of the graphene pore walls and the chemistry of the carbon phase can be independently controlled by applying different amounts and / or types of functional groups to either or both of the graphene sheet and the carbon binder phase. (Eg, reflected in percent values such as O, F, N, H etc. in the foam). In other words, by simultaneously or independently controlling both the pore size and chemical functionality at different positions in the internal structure, it is believed that many unexpected properties, synergistic effects, and usually mutually exclusive. Graphene-carbon hybrids that exhibit a combination of several unique properties (eg, one part of the structure is hydrophobic and another part is hydrophilic; or the foam structure is both hydrophobic and lipophilic) Unprecedented flexibility or maximum freedom is obtained in foam design and manufacture. A surface or material is said to be hydrophobic when water is repelled from this material or surface, and a large contact angle is formed when a water droplet is placed on the hydrophobic surface or material. A surface or material is called lipophilic if it has a strong affinity for oil and no affinity for water. The methods of the present invention can be tightly controlled over hydrophobicity, hydrophilicity and lipophilicity.

  The invention also provides an oil removal device, an oil separation device or an oil recovery device comprising the 3D graphene-carbon hybrid foam according to the invention as an oil absorption element or oil separation element. Also provided is a solvent removal or separation device comprising the 3D graphene-carbon hybrid foam as a solvent absorbing element.

  A major advantage of the use of the inventive graphene-carbon hybrid foam as an oil absorbing element is its structural integrity. Due to the notion that graphene sheets are chemically bonded by the carbon material, the resulting foam does not disintegrate upon repeated oil absorption operations. In contrast, we have found that graphene-based oil-absorbing elements made by hydrothermal reduction, vacuum-assisted filtration, or lyophilization disintegrate after two or three absorptions of oil did. In these other cases there is nothing to hold the separating graphene sheets together (other than the weak van der Waals forces present prior to first contact with the oil). When these graphene sheets get wet by oil, they can no longer return to the original shape of the oil absorbing element.

  Another great advantage of the technology of the present invention is the flexibility of the design and manufacture of an oil absorbing element that can absorb oil up to 400 times its own weight while still maintaining its structural shape (without causing significant swelling) It is sex. This amount depends on the specific pore volume of the foam, which can be mainly controlled by the ratio between the amount of original carrier polymer particles before heat treatment and the amount of graphene sheet.

  The invention also provides a method of separating / recovering oil from an oil-water mixture (e.g. water from which the oil has drained, or wastewater from an oil sand). The method comprises the steps of (a) providing an oil absorbing element comprising an integrated graphene-carbon hybrid foam, and (b) contacting an oil-water mixture with the element to absorb oil from the mixture into the element. And (c) removing the oil absorbing element from the mixture and extracting oil from the element. Preferably, the method comprises the further step (d) of recycling said element.

  Furthermore, the invention provides a method of separating an organic solvent from a solvent-water mixture or from a mixture of solvents. The method comprises the steps of (a) providing an organic solvent absorbing element comprising an integrated graphene-carbon hybrid foam, and (b) the element being an organic solvent-water mixture, or a first solvent and at least a second solvent. Contacting with a mixture of solvents including the solvent, (c) allowing the element to absorb the organic solvent from the mixture, or absorbing the first solvent from at least the second solvent, and (d) above. Removing the element from the mixture and extracting the organic solvent or the first solvent from the element. Preferably, the method comprises the further step (e) of recycling the solvent absorbing element.

  The following examples are used to illustrate some particular details regarding the best mode of practice of the present invention and should not be construed as limiting the scope of the present invention.

Example 1: Preparation of Graphene-Carbon Foam from Flakes Graphite via Solid Polymer Carrier Based on Polypropylene Powder In the experiment, 1 kg of polypropylene (PP) pellets, 50 grams of 50 mesh flake graphite (average particle size 0.18 mm) Asbury Carbons, Asbury NJ), and 250 grams of magnetic steel balls were placed in a high energy ball mill container. The ball mill was operated at 300 rpm for 2 hours. The lid of the container was removed and the stainless steel ball was removed with a magnet. It was found that the polymeric support material was covered with a dark graphene layer. The support material was placed on a 50 mesh screen to remove small amounts of untreated flake graphite.

  Then, a sample of the coated support material was immersed in tetrachloroethylene at 80 ° C. for 24 hours to dissolve the PP and disperse the graphene sheet in the organic solvent. After removing the solvent, the isolated graphene sheet powder was recovered (mostly several layers of graphene). The remaining coated support material is then compacted in a mold cavity to form a green compact, which is then heat treated in a closed crucible at 350 ° C. and then at 600 ° C. for 2 hours for graphene-carbon foam The body was made.

  In another experiment, the same batch of PP pellets and flake graphite particles (not using impact steel balls) was placed in the same high energy ball mill container and the ball mill was run for the same time under the same conditions. These results were compared to the results obtained in driving with a collision ball. Most of isolated graphene sheets isolated from PP particles by dissolving PP are single-layer graphene. Graphene-carbon foams produced by this process have high levels of porosity (lower physical density).

  Although polypropylene (PP) is used herein as an example, the carrier material for producing graphene-carbon hybrid foam is not limited to PP. The polymer may be any polymer (thermoplastic, thermosetting, rubber, wax, mastic, rubber, organic resin, etc.) as long as the polymer can be in particle form. It should be noted that uncured or partially cured thermoset resins (such as epoxide and imide based oligomers or rubbers) can be in particulate form at room temperature or lower temperatures (eg cryogenic temperatures). Thus, even partially cured thermoset resin particles can be used as a polymer carrier.

Example 2 Graphene-Carbon Hybrid Foam Using Expanded Graphite (Thickness> 100 nm) as Graphene Source and ABS as Polymer Solid Support Particles In an experiment, 5 grams of 100 grams ABS pellet as solid support material particles Into a 16 ounce plastic container with expanded graphite. The vessel was placed in an acoustic mixer (Resodyn Acoustic mixer) and treated for 30 minutes. After treatment, it was found that the support material was covered with a thin layer of carbon. A small sample of the carrier material was placed in acetone and ultrasonic energy was applied to facilitate dissolution of the ABS. The solution was filtered using a suitable filter and washed four times with additional acetone. After washing, the filtrate was dried in a vacuum oven set at 60 ° C. for 2 hours. The sample was examined by optical microscopy and found to be graphene. The remaining pellets were extruded to make graphene-polymer sheets (1 mm thick), which were then carbonized under different temperature and compression conditions to make graphene-carbon foam samples.

Example 3: Preparation of graphene-carbon hybrid foam from mesocarbon microbeads (MCMB as graphene source material) and polyacrylonitrile (PAN) fibers (as solid support particles) In one example, 100 grams of PAN fiber segments (support) Particles of length 2 mm), 5 grams of MCMB (China Steel Chemical Co., Taiwan), and 50 grams of zirconia beads were placed in a vibrating ball mill and processed for 2 hours. After the end of the treatment, when the vibratory mill was then opened it was found that the support material was covered with a dark coating of graphene sheet. Zirconia particles with distinctly different sizes and colors were removed manually. The resulting graphene coated PAN fibers were then consolidated and melted together to produce several composite films. The films were heat treated at 250 ° C. for 1 hour (in room air), 350 ° C. for 2 hours, and 1,000 ° C. for 2 hours (under an argon gas atmosphere) to obtain a graphene-carbon foam layer. Half of the carbonized foam layer was then heated to 2,850 ° C. and maintained at this temperature for 0.5 hours.

Example 4 Particles of Hardened Phenolic Resin as Polymer Carrier in a Freezer Mill In an experiment, 10 grams of phenolic resin particles are obtained from graphitized polyimide in a sample holder of a SPEX mill (SPEX Sample Prep, Metuchen, NJ) Placed with 0.25 grams of HOPG powder and magnetic stainless steel impactor. The same experiment was performed but the sample holder did not contain an impactor ball. These processes were carried out in a "dry room" at 1% humidity to reduce water condensation on the finished product. The SPEX mill was run for 10 to 120 minutes. After operation, the contents of the sample holder were classified to recover graphene-coated resin particles by removing residual HOPG powder and impactor balls (if used).

  Graphene-coated resin particles obtained in both cases (with or without impactor balls) were examined using both digital optical microscopy and scanning electron microscopy (SEM). It was observed that the thickness of the graphene sheet that encases the resin particles increased with the run time of the mill, and for the same run time, operation with an impactor resulted in a thicker graphene coating.

  The material of the graphene coated resin particles was compressed to form a green compact, which was then infiltrated with a small amount of petroleum pitch. Separately, another green compact of graphene-coated resin particles was made under comparable conditions, but no pitch penetration was attempted. The same pyrolysis process was then performed on these two compacts.

Example 5 Natural Graphite Particles as Graphene Source, Polyethylene (PE) or Nylon 6/6 Beads as Solid Support Particles, and Ceramic or Glass Beads as Impact Balls Added 0.5 kg PE in Experiment Or nylon beads (as a solid support material), 50 grams of natural graphite (graphene sheet source), and 250 grams of zirconia powder (collision ball) were placed in the container of a planetary ball mill. The ball mill was operated at 300 rpm for 4 hours. The lid of the container was removed and the zirconia beads (a different size and weight than the graphene coated PE beads) were removed by vibrating sieves. It was found that the polymer support material particles were covered with a dark graphene layer. The support material was placed on a 50 mesh screen to remove small amounts of untreated flake graphite. In another experiment, glass beads were used as the impact ball and the other ball mill operating conditions remained the same.

  Graphene-coated PE pellet material and graphene-coated nylon bead material were separately consolidated in the mold cavity, briefly heated to a temperature above the melting point of PE or nylon, and then quenched to produce two green compacts . For comparative purposes, two corresponding compacts were made from the uncoated PE pellet material and the uncoated nylon bead material. These four compacts were then subjected to pyrolysis (by heating the compacts in a chamber at 100 ° C. to 650 ° C.). The results were very surprising. It was found that the compact of graphene-coated polymer particles was converted to a graphene-carbon hybrid foam structure having dimensions comparable to the dimensions of the original compact (3 cm × 3 cm × 0.5 cm). SEM examinations of these structures indicate that the carbon phase is present near the edges of the graphene sheets, and these carbon phases serve to bond the graphene sheets together. As schematically shown in FIG. 2 (A), the carbon-bonded graphene sheet is a graphene-carbon hybrid pore wall having pores existing in the space occupied by the original polymer particle. Form a skeleton.

  In contrast, the two compacts obtained from uncoated pellets or beads shrunk to substantially two solid carbon materials having a volume of about 15% to 20% of the volume of the original compact. These highly shrunk solid materials are substantially pore free carbon materials and they are not foam materials.

Example 6: Micron-sized rubber particles as solid polymer carrier particles This experiment started with the production of micron-sized rubber particles. Using a homogenizer for 1 minute under ambient conditions resulted in a mixture of methylhydrodimethyl siloxane polymer (20 g) and vinyldimethyl terminated polymer of polydimethylsiloxane (30 g). Tween 80 (4.6 g) was added and the mixture homogenized for 20 seconds. Platinum-divinyl tetramethyldisiloxane complex (0.5 g in 15 g of methanol) was added and mixed for 10 seconds. The mixture was added to 350 g of distilled water and homogenized for 15 minutes to obtain a stable latex. The latex was heated to 60 ° C. for 15 hours. Then, anhydrous sodium sulfate (20 g) was added to the latex to de-emulsify, and silicone rubber particles were obtained by filtering under reduced pressure, washed with distilled water, and dried at 25 ° C. under reduced pressure. The particle size distribution of the obtained rubber particles was 3 to 11 μm.

  In one example, 10 grams of rubber particles, 2 grams of natural graphite, and 5 grams of zirconia beads were placed in a vibrating ball mill and processed for 2 hours. After the end of the treatment, when the vibratory mill was then opened, it was found that the rubber particles were covered with a dark coating of graphene sheet. The zirconia particles were removed manually. The resulting graphene coated rubber particles were then mixed with 5 wt% petroleum pitch (as a binder) and mechanically consolidated together to form several composite sheets. These composite sheets were then heat-treated at 350 ° C. for 1 hour, 650 ° C. for 2 hours, and 1,000 ° C. for 1 hour in a tubular furnace to obtain a graphene-carbon foam layer.

Example 7 Preparation of Graphene Fluoride Foam In a typical procedure, a sheet of graphene-carbon hybrid is fluorinated by vapor of chlorine trifluoride in a closed autoclave reactor to obtain a fluorinated graphene-carbon hybrid film Obtained. Different fluorination times could achieve different degrees of fluorination. The sheets of fluorinated graphene-carbon foam were then separately dipped into containers each containing a chloroform-water mixture. The present inventors confirmed that these foam sheets selectively absorbed chloroform from water, and the amount of absorbed chloroform increased with the degree of fluorination until the fluorine content reached 7.3% by weight (Figure 9).

Example 8 Preparation of Graphene Oxide Foam and Nitrogenated Graphene Foam A few graphene-carbon foams prepared in Example 3 are immersed in a 30% H ₂ O ₂ -water solution for ₂ to 48 hours, 2 A graphene oxide (GO) foam having an oxygen content of ̃25% by weight was obtained.

  Several GO foam samples were mixed with different ratios of urea, and the resulting mixture was heated in a microwave reactor (900 W) for 0.5 to 5 minutes. The product was washed several times with deionized water and vacuum dried. The resulting product was a nitrogenated graphene foam. The nitrogen content determined by elemental analysis was 3% to 17.5% by weight.

  It should be noted that different functionalization treatments of graphene-carbon hybrid foam were performed for different purposes. For example, a graphene oxide-carbon hybrid foam structure is particularly effective as an absorbent of oil from an oil-water mixture (i.e. oil spills on water and then mixed with one another). In this case, the integrated 3D graphene (0-15 wt% oxygen) -carbon foam structure is both hydrophobic and lipophilic (Figures 7 and 8). A surface or material is said to be hydrophobic when water is repelled from this material or surface, and a large contact angle is formed when a water droplet is placed on the hydrophobic surface or material. A surface or material is called lipophilic if it has a strong affinity for oil and no affinity for water.

  The different contents of O, F and / or N make the graphene-carbon hybrid foam according to the invention able to absorb different organic solvents from water or separate one organic solvent from a mixture of solvents It also becomes possible.

Comparative Example 1: Carbonization of Graphene and Graphene-Polymer Composite by Hummer's Method Graphite oxide can be prepared according to Hummers' method [U.S. Pat. No. 2,798,878, July 9, 1957], nitrate, and Prepared by oxidation of graphite flakes with permanganate. After completion of the reaction, the resulting mixture was poured into deionized water and filtered. The resulting graphite oxide was repeatedly washed in a 5% solution of HCl to remove most of the sulfate ion. The sample was then repeatedly washed with deionized water until the pH of the filtrate was neutral. The resulting slurry was spray dried and stored in a vacuum oven at 60 ° C. for 24 hours. The layer spacing of the resulting layered graphite oxide was about 0.73 nm (7.3 A) as measured by Debey-Scherrer's X-ray technique. A sample of this material is then placed in a furnace preset at 650 ° C. for 4 minutes for exfoliation, heated for 4 hours in an inert atmosphere furnace at 1200 ° C., and composed of several layers of reduced graphene oxide (RGO) Form a low density powder. The surface area was measured by nitrogen adsorption BET. This powder was then dry mixed with pellets of ABS, PE, PP, and nylon at loadings of 1% to 25%, respectively, and compounded using a 25 mm twin screw extruder to form a composite sheet. These composite sheets were then pyrolyzed.

Comparative Example 2: Preparation of single-layer graphene oxide (GO) sheet from mesocarbon microbeads (MCMB), followed by preparation of graphene foam layer from GO sheet Mesocarbon microbeads (MCMB) were prepared according to China Steel Chemical Co. , Kaohsiung, Taiwan. This material has a density of about 2.24 g / cm ³ and a median particle size of about 16 μm. MCMB (10 grams) was intercalated with an acid solution (sulfuric acid, nitric acid, and potassium permanganate in a ratio of 4: 1: 0.05) for 48 to 96 hours. After the reaction was complete, the mixture was poured into deionized water and filtered. The intercalated MCMB was repeatedly washed in a 5% solution of HCl to remove most of the sulfate ion. The sample was then repeatedly washed with deionized water until the pH of the filtrate was above 4.5. Next, the obtained slurry was subjected to ultrasonic treatment for 10 to 100 minutes to obtain a GO suspension. TEM and atomic force microscopy studies show that most GO sheets are single-layer graphene if the oxidation treatment exceeds 72 hours and two or three-layer graphene if the oxidation time is 48 to 72 hours Be

  These GO sheets contain an oxygen ratio of about 35% to 47% by weight for an oxidation treatment time of 48 to 96 hours. The GO sheet was suspended in water. Immediately before casting, baking soda (5-20 wt%) as a chemical blowing agent was added to the suspension. The suspension was then cast on a glass surface. Several samples were cast, some with blowing agent and some without blowing agent. The GO film obtained after removal of the liquid has a thickness which can vary from about 10 to 500 μm. Then, a sheet of several GO films with or without a foaming agent was subjected to a heat treatment including a heating temperature of 80 to 500 ° C. for 1 to 5 hours to produce a graphene foam structure.

Comparative Example 3 Preparation of Pure Graphene Foam (0% Oxygen) In recognition of the possibility of a high defect population in the GO sheet, the effect of lowering the conductivity of the individual graphene surface can be obtained. Whether it is possible to obtain graphene foams with higher thermal conductivity by using pure graphene sheets (such as non-oxidized and oxygen-free, non-halogenated and halogen-free, etc.) I decided to investigate. Pure graphene sheets were made using direct sonication (also known in the art as liquid phase exfoliation).

  In a typical procedure, 5 grams of graphite flakes ground to a size of about 20 μm or less in 1,000 mL of deionized water (with 0.1 wt% dispersant) Zonyl® FSO from DuPont Dispersed in, a suspension was obtained. An ultrasonic energy level of 85 W (Branson S450 Ultrasonicator) was used for a period of 15 minutes to 2 hours for exfoliation, separation, and size reduction of graphene sheets. The obtained graphene sheet is a non-oxidized, oxygen-free, relatively defect-free pure graphene. Pure graphene is essentially free of non-carbon elements.

Chemical Graphing Agent (N, N-dinitrosopentamethylenetetramine or 4,4'-oxybis (benzenesulfonylhydrazide)) in various amounts (1 wt% to 30 wt% relative to the graphene material), pure graphene sheet And added to the suspension containing the surfactant. The suspension was then cast on a glass surface. Several samples were cast and included samples using CO ₂ as a physical blowing agent introduced into the suspension just prior to casting. The graphene film obtained after removal of the liquid has a thickness which can vary from about 10 to 100 μm. Then, heat treatment was performed on these graphene films at 80 to 1,500 ° C. for 1 to 5 hours to prepare graphene foams.

Comparative Example 4: CVD Graphene Foam on Ni Foam Template Chen, Z., et al. et al. "Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapor deposition," Nat. Mater. The procedure disclosed in 10, 424-428 (2011) was adapted. Porous structured nickel foam with nickel interconnected 3D scaffold was chosen as a template for the growth of graphene foam. Briefly, carbon was introduced into the nickel foam by decomposing CH ₄ at 1,000 ° C. under ambient pressure, and then a graphene film was deposited on the surface of the nickel foam. Corrugations and wrinkles were formed on the graphene film due to the difference in thermal expansion coefficient between nickel and graphene. In order to recover (separate) the graphene foam, it is necessary to etch away the Ni frame. A thin layer of poly (methyl methacrylate) (PMMA) as a support to prevent the collapse of the graphene network during etching of nickel before etching away the nickel skeleton with a hot HCl (or FeCl ₃ ) solution It was deposited on the surface of graphene film. After careful removal of the PMMA layer with hot acetone, brittle graphene foam samples were obtained. The use of a PMMA support layer is important for making free-standing films of graphene foam, and without the use of a PMMA support layer, a very broken and deformed graphene foam sample was obtained. This is a time-consuming way that is not environmentally friendly and adaptable.

Comparative Example 5: Conventional Graphite Foam From Pitch Based Carbon Foam The powder, granules, or pellets of pitch are placed in an aluminum mold having the desired final shape of the foam. A Mitsubishi ARA-24 mesophase pitch was used. The sample is evacuated to less than 1 Torr and then heated to a temperature of about 300.degree. At this point, the vacuum was released to a nitrogen blanket and then a pressure of up to 1,000 psi was applied. The temperature of the system was then raised to 800.degree. This was done at a rate of 2 ° C./min. The temperature was maintained for at least 15 minutes to achieve immersion, then the furnace was turned off and cooled to room temperature at a rate of about 1.5 ° C./min, with which the pressure was released at a rate of about 2 psi / min. The final foam temperature was 630.degree. C. and 800.degree. During the cooling cycle, the pressure is gradually released to atmospheric conditions. The foam was then heat treated (carbonized) to 1050 ° C. under a nitrogen blanket and then separately heat treated (graphitized) to 2500 ° C. and 2800 ° C. in argon in a graphite crucible.

Comparative Example 6: Graphene foam from hydrothermally reduced graphene oxide For comparison, a self-assembled graphene hydrogel (SGH) sample was prepared by a one-step hydrothermal method. In a typical procedure, SGH can be easily prepared by heating a 2 mg / mL homogeneous graphene oxide (GO) aqueous dispersion sealed in a Teflon lined autoclave for 12 hours at 180 ° C. . An SGH comprising about 2.6% (by weight) of graphene sheet and 97.4% water has a conductivity of about 5 × 10 ⁻³ S / cm. After drying and heat treatment at 1,500 ° C., the resulting graphene foam exhibits a conductivity of about 1.5 × 10 ⁻¹ S / cm, which is a graphene according to the invention produced by heat treatment at the same temperature It is half the conductivity of the foam.

Example 9 Thermal and Mechanical Testing of Various Graphene Foams and Conventional Graphite Foams Samples obtained from various conventional carbon or graphene foam materials were machined into specimens for thermal conductivity measurements. . The bulk thermal conductivity of the mesophase pitch derived foam was in the range of 67 W / mK to 151 W / mK. The density of the sample was 0.31 to 0.61 g / cm ³ . When considering the weight, the specific thermal conductivity of foam derived from pitch is about 67 / 0.31 = 216 and 151 / 0.61 = 247.5 W / mK per unit specific gravity (or per unit physical density) .

The compressive strength of the sample having an average density of 0.51 g / cm ³ was measured to be 3.6 MPa, and the compressive elastic modulus was measured to be 74 MPa. In contrast, the compressive strength and compressive modulus of the graphene-carbon foam sample according to the invention with comparable physical density are 6.2 MPa and 113 MPa, respectively.

FIG. 4 (A) shows the thermal conductivity versus specific gravity of 3D graphene-carbon foam, graphite foam derived from mesophase pitch, and Ni foam template assisted CVD graphene foam. These data clearly show the following unexpected results:
1) 3D-integrated graphene-carbon foams produced by the method according to the invention are significantly more comparable to both mesophase pitch-derived graphite foam and Ni foam template-assisted CVD graphene for the same physical density It exhibits high thermal conductivity.

  2) This takes into account the notion that CVD graphene is substantially pure graphene that has not been oxidized, and should have a higher thermal conductivity than our graphene-carbon hybrid foams Then it is very surprising. The carbon phase of the hybrid foam is generally low in crystallinity (some of which is amorphous carbon), and thus has a much lower thermal conductivity or conductivity compared to graphene alone. However, when the carbon phase combines with the graphene sheet to form an integral structure formed by the method according to the invention, the resulting hybrid form has a thermal conductivity compared to completely pure graphene foam Indicates These very high thermal conductivity values observed for graphene-carbon hybrid foams made according to the present invention are very surprising to the present inventors. This is believed to be due to the observation that otherwise isolated graphene sheets are bound by the carbon phase in this case to form a bridge for the continuous transport of electrons and phonons.

  3) The specific conductivity value of the hybrid foam material according to the present invention shows a value of 250 to 500 W / mK per unit specific gravity, but the value of other kinds of foam materials is typically 250 W / mK per unit specific gravity Less than.

  4) The thermal conductivity data of a series of 3D graphene-carbon foams and a series of pure graphene-derived foams are summarized in FIG. 5, both plotted over the final (maximum) heat treatment temperature. Thermal conductivity increases monotonically with the final HTT for both types of materials. However, the method according to the invention allows cost-effective and environmentally friendly production of graphene-carbon foams superior to pure graphene foams. This is another unexpected result.

  5) FIG. 4 (B) shows the thermal conductivity value of the hybrid foam according to the present invention and the hydrothermally reduced GO graphene foam. In FIG. 6, the conductivity values of 3D graphene-carbon foam and hydrothermally reduced GO graphene foam are shown. These data further support the notion that, for the same amount of solid material, the graphene-carbon foam according to the invention is largely conductive in nature and reflects the remarkable continuity of the electron and phonon transport pathways doing. The carbon phase fills in the gaps or breaks between the graphene sheets.

Example 10: Characterization of Various Graphene Foams and Conventional Graphite Foams The internal structure (crystal structure and orientation) of several series of graphene-carbon foam materials was investigated using X-ray diffraction. The x-ray diffraction curve of natural graphite typically shows a peak at approximately 2θ = 26 °, corresponding to a graphene spacing (d ₀₀₂ ) of about 0.3345 nm. The graphene walls of the hybrid foam material typically exhibit d ₀₀₂ spacing of 0.3345 nm to 0.40 nm, more typically up to 0.34 nm.

Using a heat treatment temperature of 2750 ° C. under compression for 1 hour for the foam structure reduces the d ₀₀₂ spacing to about 0.3354 nm, which is the same as the value for graphite single crystals. In addition, a high intensity second diffraction peak appears at 2θ = 55 °, which corresponds to X-ray diffraction from the (004) plane. The (004) peak intensity to the (002) intensity on the same diffraction curve, ie, the I (004) / I (002) ratio, is a good indicator of the degree of crystal perfection and the preferred orientation of the graphene surface. For any graphite material heat treated at a temperature less than 2,800 ° C., the (004) peak is either absent or relatively weak, with an I (004) / I (002) ratio of <0. It is 1. The I (004) / I (002) ratio of the heat treated (for example, highly oriented pyrolytic graphite, HOPG) graphite material at 3,000 to 3,250 ° C. is in the range of 0.2 to 0.5. In contrast, graphene foams made in one hour at a final HTT of 2750 ° C. show an I (004) / I (002) ratio of 0.78 and a mosaic spread value of 0.21, with pore walls Indicates that the graphene is substantially complete graphene single crystal and has a favorable degree of preferred orientation (when fabricated under compressive force).

  The "mosaic spread" value is obtained from the full width at half maximum of (002) reflection in the x-ray diffraction intensity curve. The index of the degree of order characterizes the crystal size (or grain size) of graphite or graphene, the amount of grain boundaries and other defects, and the preferred grain orientation. An almost perfect single crystal of graphite is characterized by having a mosaic spread value of 0.2 to 0.4. Some of our graphene foams have mosaic spread values within this 0.3 to 0.6 range when manufactured using a final heat treatment temperature of 2,500 ° C. or higher.

The following is a summary of some of the more prominent results:
1) In general, the addition of collision balls helps to accelerate the exfoliation process of graphene sheets from graphite particles. However, this option requires the separation of these impact balls after the graphene coated polymer particles are made.

  2) Hardened polymer particles (eg PE, PP, nylon, ABS, polystyrene, high impact polystyrene etc.) and their fillers reinforced if collision balls (eg ceramic, glass, metal balls etc) are not used Versions have a higher ability to exfoliate the graphene sheet from the graphite particles than softer polymer particles (eg, rubber, PVC, polyvinyl alcohol, latex particles).

  3) Graphene with 0.001 wt% to 5 wt% of graphene (mostly single-layer graphene sheet), with softer polymer particles, in the case of the same 1 hour operation time, when no collision ball is added externally Coated or graphene-embedded particles tend to be obtained, and harder polymer balls result in graphene-coated particles with 0.01 wt% to 30 wt% of graphene (mostly monolayer and few-layer graphene sheets) There is a tendency.

  4) When using externally added collision balls, all polymer balls are from 0.001 wt% to about 80 wt% graphene sheets (mostly few layers graphene, more than 30 wt% graphene sheets <10 Layer) can be supported.

  5) Graphene-carbon hybrid foam materials according to the present invention typically have significantly higher structural integrity (eg compressive strength, elasticity, etc.) compared to their counterparts produced by conventional prior art methods And elasticity) and high thermal conductivity and conductivity.

6) All prior art methods of making graphite foam or graphene foam yield macroporous foams having physical densities in the range of only about 0.2 to 0.6 g / cm ³ It is important to note that the pore size is typically too large (e.g. 20-300 [mu] m) for most of the intended applications. In contrast, the present invention provides a method of producing graphene foam having a density that can be as low as 0.001 g / cm ³ and as high as 1.7 g / cm ³ . Their pore size can vary from microscopic (<2 nm) to meso scale (2 to 50 nm) and up to macro scale (eg 1 to 500 μm). This level of freedom and versatility in the design of various types of graphene-carbon foams is unprecedented and can not be reached by any prior art method.

  7) The method according to the present invention may have a chemical composition (eg, recovery of oil from water contaminated with oil, separation of organic solvent from water or another solvent, release of heat, etc.) depending on the requirements of various applications It also enables convenient and flexible control over the content of F, O, and N, etc.).

  In conclusion, we have successfully developed a completely new, novel, unexpected and distinctly different kind of high conductivity graphene-carbon hybrid foam material, device and related manufacturing method. The chemical composition (oxygen, fluorine, and% of other non-carbon elements), structure (crystal integrity, grain size, defect clusters etc), crystal orientation, morphology, manufacturing method and properties of this new type of foam material The mesophase pitch-derived graphite foam, the CVD graphene-derived foam, and the graphene foam obtained from the hydrothermal reduction of GO are fundamentally different from and distinct from each other.

Claims (41)

An integrated 3D graphene-carbon hybrid foam composed of a plurality of pores and pore walls, wherein the pore walls are by a carbon material having a carbon material to graphene weight ratio of 1/200 to 1/2. 2 to 10 stacked graphene planes comprising chemically bound single or several layer graphene sheets, said few layers graphene sheets having a spacing d _{002 of} 0.3354 nm to 0.40 nm, measured by X-ray diffraction And the single-layer or few-layer graphene sheet comprises pure graphene material having substantially 0% non-carbon element, or impure graphene material having 0.001% to 25% non-carbon element by weight. Wherein said impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, water An integrated 3D graphene-carbon hybrid foam selected from hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof. The 3D graphene foam has a density of 0.005 to 1.7 g / cm ³ , a specific surface area of 50 to 3,200 m ² / g, a thermal conductivity of at least 200 W / m K per unit specific gravity, and / or per unit specific gravity The integrated 3D graphene-carbon hybrid foam according to claim 1, having a conductivity of 2,000 S / cm or more. The integrated type according to claim 1, wherein the pore wall comprises pure graphene, and the 3D graphene-carbon hybrid foam has a density of 0.01 to 1.7 g / cm ³ or an average pore diameter of 2 to 50 nm. 3D Graphene-Carbon Hybrid Foam.   The pore wall comprises impure graphene material, the foam comprises a non-carbon element content in the range of 0.01 wt% to 20 wt%, and the non-carbon element comprises oxygen, fluorine, chlorine, bromine, The integrated 3D graphene-carbon hybrid foam according to claim 1, comprising an element selected from iodine, nitrogen, hydrogen or boron.   The integrated 3D graphene-carbon hybrid foam of claim 1, wherein the pore wall comprises graphene fluoride and the solid graphene foam comprises 0.01 wt% to 15 wt% fluorine content.   The 3D graphene-carbon hybrid foam of claim 1, wherein the pore wall comprises graphene oxide and the solid graphene foam comprises an oxygen content of 0.01 wt% to 20 wt%. The 3D graphene-carbon hybrid foam according to claim 1, wherein the foam has a specific surface area of 200 to 3,000 m ² / g or a density of 0.1 to 1.2 g / cm ³ .   The 3D graphene-carbon hybrid foam according to claim 1, in the form of a continuous long roll sheet having a thickness of 100 nm to 10 cm, and a length of at least 2 meters, and manufactured by a roll-to-roll process.   The foam has an oxygen or non-carbon content of less than 1% by weight, the pore walls have a graphene spacing of less than 0.35 nm, a thermal conductivity of at least 250 W / mK per unit specific gravity, and / or The 3D graphene-carbon hybrid foam according to claim 1, having a conductivity of 2,500 S / cm or more per unit specific gravity.   Said foam having an oxygen content or non-carbon content of less than 0.01% by weight, said pore walls being graphene spacings of less than 0.34 nm, thermal conductivity of at least 300 W / mK per unit specific gravity, and The 3D graphene-carbon hybrid foam according to claim 1, comprising stacked graphene surfaces having a conductivity of 3,000 S / cm or more per unit specific gravity.   The foam has an oxygen content or non-carbon content of 0.01% by weight or less, the pore walls have graphene spacing less than 0.336 nm, a thermal conductivity of at least 350 W / mK per unit specific gravity, The 3D graphene foam according to claim 1, comprising laminated graphene surfaces having a conductivity of at least 3,500 S / cm per unit specific gravity.   A pore wall comprising a laminated graphene surface wherein said foam has a graphene spacing of less than 0.336 nm, a thermal conductivity of more than 400 W / mK per unit specific gravity, and / or a conductivity of more than 4,000 S / cm per unit specific gravity. The 3D graphene-carbon hybrid foam according to claim 1, having   The 3D graphene-carbon hybrid foam according to claim 1, wherein the pore wall comprises laminated graphene surfaces having a graphene spacing of less than 0.337 nm and a mosaic spread value of less than 1.0.   The 3D graphene-carbon hybrid foam of claim 1, wherein the pore wall comprises a 3D network of interconnected graphene planes.   The 3D graphene-carbon hybrid foam of claim 1, wherein the foam comprises mesoscale pores having a pore size of 2 nm to 50 nm.   An oil removal device or oil separation device comprising the 3D graphene-carbon hybrid foam according to claim 1 as an oil absorbing element.   A solvent removal or separation device comprising the 3D graphene-carbon hybrid foam according to claim 1 as solvent absorption or separation element. How to separate oil from water:
a. Providing an oil-absorbing element comprising the integrated 3D graphene-carbon hybrid foam according to claim 1;
b. Contacting an oil-water mixture with the element to cause the element to absorb the oil from the mixture;
c. Removing the element from the mixture and extracting the oil from the element;
d. Reusing the element;
Method including. A method of separating an organic solvent from a solvent-water mixture or from a mixture of solvents:
a. Providing an organic solvent absorbing element or solvent separating element comprising the integrated 3D graphene-carbon hybrid foam according to claim 1;
b contacting the element with an organic solvent-water mixture, or a mixture of solvents including a first solvent and at least a second solvent;
c. Allowing the element to absorb the organic solvent from the mixture, or separating the first solvent from the at least second solvent by the element;
d. Removing the element from the mixture and extracting an organic solvent or a first solvent from the element;
e. Reusing the element;
Method including.   A thermal management device comprising the 3D integrated graphene-carbon hybrid foam according to claim 1 as a heat spreading or heat dissipating element.   Heat exchangers, heat sinks, heat pipes, highly conductive inserts, conductive plates between heat sinks and heat sources, heat spreaders, heat spreaders, heat interface media, or devices selected from thermal electrical coolers or Peltier coolers 21. A thermal management device according to claim 20, comprising. A method of directly producing integrated 3D graphene-carbon hybrid foam from a graphite material:
(A) mixing the plurality of particles of the graphite material and the plurality of particles of the solid polymer support material in a collision chamber of the energy collision apparatus to form a mixture;
(B) peeling a graphene sheet from the graphite material and transferring the graphene sheet to the surface of the solid polymer carrier material particles to form graphene coated polymer particles or graphene embedded polymer particles inside the collision chamber Operating the energy collision device for a sufficient time, for a certain frequency and for a certain intensity;
(C) recovering said graphene coated polymer particles or graphene embedded polymer particles from said collision chamber to solidify said graphene coated polymer particles or graphene embedded polymer particles into a desired shape of a graphene-polymer composite structure;
(D) Thermally decomposing the shape of the graphene-polymer composite structure and thermally converting the polymer into pores or carbon or graphite that bonds the graphene sheet, thereby forming an integrated 3D graphene-carbon hybrid foam Forming steps,
Method including.   23. The method of claim 22, wherein a plurality of collision balls or media are added to the collision chamber of the energy collision device.   24. The method of claim 23, wherein step (c) comprises manipulating a magnet to separate the collision ball or medium from the graphene coated polymer particle or graphene embedded polymer particle.   The method according to claim 22, wherein the solid polymer material particles comprise plastic or rubber beads, pellets, spheres, wires, fibers, filaments, disks, ribbons or rods having a diameter or thickness of 10 nm to 10 mm.   26. The method of claim 25, wherein the diameter or thickness is 100 nm to 1 mm.   The method according to claim 22, wherein the solid polymer is selected from solid particles of thermoplastics, thermosetting resins, rubbers, semi-penetrating network polymers, penetrating network polymers, natural polymers, or combinations thereof.   23. The method of claim 22, wherein prior to step (d), the solid polymer is partially removed by melting, etching or dissolution in a solvent.   The graphite material is natural graphite, rigid graphite, highly oriented pyrolytic graphite, graphite fiber, graphite nanofiber, fluorinated graphite, graphite oxide, chemically modified graphite, exfoliated graphite, exfoliated and recompressed graphite, expanded graphite, meso carbon 23. The method of claim 22, wherein the method is selected from microbeads, or a combination thereof.   The energy collision apparatus includes a vibration ball mill, a planetary ball mill, a high energy mill, a basket mill, an agitator ball mill, a cryo ball mill, a micro ball mill, a tumble ball mill, a continuous ball mill, a stirring ball mill, a pressure ball mill, a freezer mill, a vibrating sieve, a bead mill, nano The method according to claim 22, wherein the method is a bead mill, an ultrasonic homogenizer mill, a centrifugal planetary mixer, a vacuum ball mill, or a resonance acoustic mixer.   23. The method of claim 22, wherein the graphite material comprises a non-intercalated, non-oxidized graphite material that has not been previously treated with chemical and oxidative treatments prior to the mixing step.   The solid polymer is a phenolic resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polybenzothiazole, polybenzobisthiazole, poly (p-phenylene) 23. The method of claim 22, comprising a high carbon yield polymer selected from vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof.   The solid polymer is polyethylene, polypropylene, polybutylene, polyvinyl chloride, polycarbonate, acrylonitrile-butadiene (ABS), polyester, polyvinyl alcohol, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene 23. The method of claim 22, comprising a low carbon yield polymer selected from oxide (PPO), polymethyl methacrylate (PMMA), their copolymers, their polymer blends, or combinations thereof.   The step of thermal decomposition carbonizes the polymer at a temperature of 200 ° C. to 2,500 ° C. to obtain a graphene-carbon foam, or carbonizes it at a temperature of a temperature of 200 ° C. to 2,500 ° C. The method according to claim 22, comprising obtaining a graphene-carbon foam, and then graphitizing the graphene-carbon foam at 2,500 ° C to 3,200 ° C to obtain a graphitized graphene-carbon foam. Method.   The solidifying step melts the polymer particles to form a polymer melt mixture in which graphene sheets are dispersed, forming a desired shape from the polymer melt mixture, and the shape being graphene-polymer composite Solidifying the structure.   The solidifying step dissolves the polymer particles in a solvent to form a polymer solution mixture in which a graphene sheet is dispersed, forms a desired shape from the polymer solution mixture, and removes the solvent. Solidifying the shape into the graphene-polymer composite structure.   23. The method of claim 22, wherein said solidifying step comprises forming from said graphene coated polymer particles a composite shape selected from the form of rods, sheets, films, fibers, powders, ingots, or blocks.   Said solidifying step compacts said graphene-coated polymer particles into macroporous porous green compacts, then petroleum pitch, coal tar pitch, aromatic organic material, monomer, organic polymer, or Permeating or impregnating additional carbon source material selected from the combination thereof into the pores.   The organic polymer is a phenol resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polybenzothiazole, polybenzobisthiazole, poly (p-phenylene) 39. The method of claim 38, comprising a high carbon yield polymer selected from vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof.   23. The method of claim 22, wherein the solidifying step comprises forming a compact from the material of the graphene coated polymer particles or graphene embedded polymer particles. 41. The method of claim 40, wherein the compact is in a form selected from rods, sheets, films, fibers, powders, ingots, or blocks.

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