KR102584293B1 - Graphene-carbon hybrid foam - Google Patents

Abstract

An integrated 3D graphene-carbon hybrid foam composed of multiple pores and pore walls, wherein the pore walls are composed of single-layer or few-layer graphene chemically bonded by carbon material with a carbon material-to-graphene weight ratio of 1/100 to 1/2. Comprising a fin sheet, the few-layer graphene sheet has 2 to 10 layers of overlapping graphene planes with an interplanar spacing d ₀₀₂ of 0.3354 nm to 0.40 nm, and the graphene sheet is pure (essentially 0% non-carbon elements). pristine) graphene material, or non-pristine graphene material having 0.01% to 25% by weight of non-carbon elements, wherein the non-pure graphene includes graphene oxide, reduced graphene oxide, 3D graphene selected from graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, graphene nitride, doped graphene, chemically functionalized graphene, or combinations thereof. Provides a carbon hybrid foam. Additionally, methods for producing hybrid foams, products containing the hybrid foams, and uses thereof are provided.

Description

Graphene-carbon hybrid foam

Cross-reference to related applications

This application claims priority from U.S. Patent Application Nos. 14/998,356 and 14/998,357, respectively, filed December 28, 2015, which are incorporated herein by reference.

Technology field

The present invention relates generally to carbon/graphite foams, and more specifically to a new type of porous graphite material, referred to herein as integral 3D graphene-carbon hybrid foam, methods of making the same, products comprising the same, and products thereof. It's about how to make it work.

Carbon is used in diamonds, fullerenes (0-D nano-graphitic materials), carbon nanotubes or carbon nanofibers (1-D nano-graphitic materials), graphene (2-D nano-graphitic materials), and graphite (3-D nano-graphitic materials). It is known to have five unique crystal structures, including . Carbon nanotubes (CNTs) are tube structures grown with single or multiple walls. Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have a diameter of approximately several nanometers to hundreds of nanometers. Its longitudinally hollow structure gives the material unique mechanical, electrical, and chemical properties. CNTs or CNFs are one-dimensional nanocarbon or 1-D nanographite materials.

Our research group pioneered the development of graphene materials and related manufacturing processes as early as 2002: (1) B. Z. Jang and W. C. Huang, "Nano-scaled Graphene Plates," U.S. Patent No. 7,071,258 (July 4, 2006) , filed October 21, 2002; (2) B. Z. Jang, et al. “Process for Producing Nano-scaled Graphene Plates,” U.S. Patent Application No. 10/858,814 (June 3, 2004); and (3) B. Z. Jang, A. Zhamu, and J. Guo, “Process for Producing Nano-scaled Platelets and Nanocomposites,” U.S. Patent Application No. 11/509,424 (August 25, 2006).

Single-layer graphene sheets are composed of carbon atoms occupying a two-dimensional hexagonal lattice. Multi-layer graphene is a platelet composed of more than one graphene plane. Individual single-layer graphene sheets and multilayer graphene platelets are collectively referred to herein as nanographene platelets (NGP) or graphene materials. NGP consists of pristine graphene (essentially 99% carbon atoms), slightly oxidized graphene (less than 5% oxygen by weight), graphene oxide (more than 5% oxygen by weight), and slightly fluorinated graphene (5% fluorine by weight). %), graphene fluoride (more than 5% by weight fluorine), other halogenated graphene, and chemically functionalized graphene.

NGPs have been found to have a variety of unusual physical, chemical, and mechanical properties. For example, graphene has been found to have the highest intrinsic strength and highest thermal conductivity of all existing materials. Applications of graphene in real-world electronics (e.g., replacing Si as the backbone of transistors) are not expected to be realized within the next five to 10 years, but it has also been used as a nanofiller in composites and in energy storage devices. The application of graphene as an electrode material is imminent. To successfully utilize graphene in composites, energy and other fields, it is essential that processable graphene sheets be available in large quantities.

This research group was one of the first to discover 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 US Patent No. 7,071,258 (July 4, 2006)]. This research group recently reviewed the manufacturing process of NGP and NGP nanocomposites [Bor Z. Jang and A Zhamu, "Processing of Nano Graphene Platelets (NGPs) and NGP Nanocomposites: A Review," J. Materials Sci. 43 (2008) 5092-5101]. In the prior art, NGPs were prepared following four main approaches. A brief summary of its advantages and disadvantages is as follows:

A review of the fabrication of free-standing nanographene plates or sheets (NGP)

Approach 1: Chemical formation and reduction of graphene oxide (GO)

The first approach (Figure 1) treats natural graphite powder with an intercalating agent and an oxidizing agent (e.g. concentrated sulfuric acid and nitric acid, respectively) to obtain a graphite intercalation compound (GIC), or actually graphite. It involves obtaining oxide (GO) [William S. Hummers, Jr., et al., Preparation of Graphitic Oxide, Journal of the American Chemical Society, 1958, p. 1339]. The interplanar spacing of graphene before insertion or oxidation is about 0.335 nm ( L _d = ½ d ₀₀₂ = 0.335 nm). By intercalation and oxidation treatment, the intergraphene spacing is typically increased to values exceeding 0.6 nm. This is the first expansion stage that the graphitic material undergoes during the chemical pathway. The resulting GIC or GO is then subjected to further expansion (commonly referred to as “exfoliation”) using either a thermal shock exposure approach or a solution-based ultrasound-assisted graphene layer exfoliation approach.

In the thermal shock exposure approach, GIC or GO is exposed to high temperatures (typically 800 to 1,050°C) for a short period of time (typically 15 to 60 seconds) to exfoliate or expand the GIC or GO, resulting in exfoliation or additional expanded graphite (typically It forms a "graphite worm" consisting of graphite flakes that are still interconnected with each other. This thermal shock method can produce a few isolated graphite flakes or graphene sheets, but usually most of the graphite flakes remain interconnected. Typically, the exfoliated graphite or graphite worms are then subjected to flake separation using air milling, mechanical shearing or submersible sonication. Approach 1 therefore essentially involves three distinct processes: primary expansion (oxidation or intercalation), further expansion (or "exfoliation"), and separation.

In the solution-based separation approach, the swollen or exfoliated GO powder is dispersed in water or an aqueous alcohol solution and sonicated. It is important to note that in these processes sonication is used after insertion and oxidation of the graphite (i.e. after primary expansion), and typically after thermal shock exposure of the resulting GIC or GO (i.e. after secondary expansion). . Alternatively, GO powder dispersed in water undergoes ion exchange or a lengthy purification process in such a way that the repulsion between ions in the spaces between the planes overcomes the inter-graphene van der Waals forces, resulting in the separation of the graphene layers. .

There are several major problems associated with these conventional chemical manufacturing processes:

(1) This process requires the use of large amounts of several undesirable chemicals, such as sulfuric acid, nitric acid, and potassium permanganate or sodium chlorate.

(2) The chemical treatment process requires a long time (usually 5 hours to 5 days) for insertion and oxidation.

(3) During this lengthy intercalation or oxidation process, strong acids consume significant amounts of graphite by “burrowing into the graphite” (i.e., converting graphite to carbon dioxide, which is lost in the process). It is common for 20 to 50% by weight of graphite material to be lost when immersed in strong acids and oxidizing agents.

(4) Thermal peeling requires high temperatures (typically 800-1,200°C), so it is a highly energy-intensive process.

(5) Both heat-induced exfoliation and solution-induced exfoliation approaches require very demanding cleaning and purification steps. For example, 2.5 kg of water is typically used to clean and recover 1 g of GIC, resulting in a large amount of wastewater that must be properly treated.

(6) In both heat-induced exfoliation and solution-induced exfoliation approaches, the resulting products are GO platelets that must undergo further chemical reduction treatment to reduce the oxygen content. Typically, even after reduction, the electrical conductivity of GO platelets remains much lower than that of pure graphene. Additionally, reduction procedures often involve the use of toxic chemicals such as hydrazine.

(7) Additionally, the amount of embedding solution remaining in the flakes after drainage may be 20 to 150 parts by weight (pph), more typically about 50 to 120 pph, based on 100 parts by weight of graphite flakes. During high-temperature exfoliation, residual intercalated species retained by the flakes decompose to produce various undesirable species of sulfur and nitrogen compounds (eg, NO _x and SO _x ). To avoid adverse effects on the environment, emissions require costly remediation processes.

The present invention is intended to overcome the limitations or problems outlined above.

Approach 2: Direct formation of pure nanographene platelets

In 2002, our research team succeeded in isolating single-layer and multi-layer graphene sheets from partially carbonized or graphitized polymer carbon obtained from polymer or pitch precursors [B. Z. Jang and W. C. Huang, “Nano-scaled Graphene Plates,” U.S. Patent Application No. 10/274,473 (filed October 21, 2002); Current U.S. Patent No. 7,071,258 (July 4, 2006)]. Mack et al. ["Chemical manufacture of nanostructured materials" U.S. Patent No. 6,872,330 (March 29, 2005)] inserted potassium melt into graphite and brought the resulting K-inserted graphite into contact with alcohol to form a roughly exfoliated graphite. A process involving preparing graphite-containing NGPs was developed. Because pure alkali metals such as potassium and sodium are extremely sensitive to moisture and pose a risk of explosion, this process must be performed carefully in a vacuum or extremely dry glove box environment. This process is not suitable for mass production of NGP. The present invention is intended to overcome the limitations outlined above.

Approach 3: Epitaxial growth and chemical vapor deposition of nanographene sheets on inorganic crystal surfaces

Small-scale fabrication of ultrathin graphene sheets on substrates can be achieved by thermal decomposition-based epitaxial growth and laser desorption-ionization techniques [Walt A. DeHeer, Claire Berger, Phillip N. First, "Patterned thin film graphite “devices and method for making same” U.S. Patent No. 7,327,000 B2 (June 12, 2003)]. Epitaxial films of graphite, which have only one or a few atomic layers, are technologically and scientifically important due to their unique properties and great potential as device substrates. However, this process is not suitable for mass production of free-standing graphene sheets for composite materials and energy storage applications. The present invention is intended to overcome the limitations outlined above.

Another process for producing graphene in thin film form (typically less than 2 nm thick) is the catalytic chemical vapor deposition process. This catalytic CVD involves catalytic decomposition of a hydrocarbon gas (eg, C ₂ H ₄ ) on a Ni or Cu surface to form single-layer or few-layer graphene. When Ni or Cu is the catalyst, carbon atoms obtained through decomposition of hydrocarbon gas molecules at a temperature of 800 to 1,000°C are deposited directly on the surface of the Cu foil or precipitated from the Ni-C solid solution state to the surface of the Ni foil and form a single Form a single-layer or few-layer graphene (less than 5-layer) sheet. Ni-catalyzed or Cu-catalyzed CVD processes are not suitable for depositing more than 5 graphene planes (typically less than 2 nm) as the underlying Ni or Cu layer can no longer provide any catalytic effect. CVD graphene film is very expensive.

Approach 4: Bottom-up approach (graphene synthesis from small molecules)

Yang et al. [“Two-dimensional Graphene Nano-ribbons,” J. Am. Chem. Soc. 130 (2008) 4216-17] uses a method starting with Suzuki-Miyaura coupling of 1,4-diiodo-2,3,5,6-tetraphenyl-benzene and 4-bromophenylboronic acid. Thus, nanographene sheets with a length of up to 12 nm were synthesized. The resulting hexaphenylbenzene derivative was further derivatized and ring fused into small graphene sheets. This is a slow process that has so far produced very small graphene sheets. The present invention is intended to overcome the limitations outlined above.

Therefore, a reduction in the amount of undesirable chemicals (or elimination of all such chemicals), shorter process times, less energy consumption, lower degree of graphene oxidation, and release of undesirable chemical species into the drainage fluid ( There is a pressing need for graphene manufacturing processes that require the reduction or elimination of emissions (eg, sulfuric acid) or emissions into the air (eg, SO ₂ and NO ₂ ). The process should be able to produce graphene sheets that are purer (less oxidized and less damaging), more electrically conductive, and larger/wider. Additionally, these graphene sheets should be easily made into a foam structure.

Recent research by this research group has led to the development of a method for producing free-standing nano graphene platelets without chemicals, which is novel in that it does not follow the conventional methods for manufacturing nano graphene plates outlined above. Additionally, the utility of this method is enhanced in that it is cost-effective and provides novel graphene materials with significantly reduced environmental impact. Additionally, as disclosed herein, chemical-free graphene preparation and formation of graphene-carbon hybrid foam were integrated into one single process.

For the purposes of defining the claims of this application, NGP or graphene materials include single-layer and multi-layer (typically less than 10 layers) pure graphene, graphene oxide, reduced graphene oxide (RGO), graphene fluoride, Graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, graphene nitride, chemically functionalized graphene, discrete sheets of doped graphene (e.g. doped with B or N)/ Includes plate-shaped bodies. Pure graphene has essentially 0% oxygen. RGO typically has an oxygen content of 0.001% to 5% by weight. Graphene oxide (including RGO) can have between 0.001% and 50% oxygen by weight. Besides pure graphene, all graphene materials have from 0.001% to 50% by weight of non-carbon elements (e.g. O, H, N, B, F, Cl, Br, I, etc.). These materials are referred to herein as non-pristine graphene materials. The graphene-carbon foam of the present invention may comprise pure or impure graphene and the method of the present invention allows for this flexibility.

A review of graphene foam manufacturing

Generally speaking, foams or foamed materials are composed of pores (or cells) and pore walls (solid material). The pores can be interconnected to form an open-cell foam. Graphene foam is composed of pore walls and pores containing graphene material. There are three main ways to prepare graphene foam:

The first method typically involves sealing an aqueous suspension of graphene oxide (GO) in a high-pressure autoclave and storing the GO suspension at high pressure (tens or hundreds of atmospheres) and typically in the range of 180-300°C for a long time (typically 12-36 hours). Hydrothermal reduction of graphene oxide hydrogel involving heating. Useful references for this method include: Y. 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) This method is impractical for industrial scale manufacturing as it requires high pressure. First of all, this method cannot be performed continuously. (b) It is difficult, if not impossible, to control the pore size and porosity level of the pore structures produced by this method. (c) The reduced graphene oxide (RGO) material prepared by this method is inflexible in terms of variety of shapes and sizes (e.g., cannot be formed into films). (d) This method involves the use of very low concentrations of GO (e.g., 2 mg/mL = 2 g/L = 2 kg/kL) suspended in water. With the removal of non-carbon elements (up to 50%), it is only possible to produce less than 2 kg of graphene material (RGO) per 1000 liters of suspension. Additionally, it is practically impossible to operate a 1000 liter reactor that must withstand high temperature and high pressure conditions. Clearly, this method is not scalable for mass production of porous graphene structures.

The second method is based on a template-assisted catalytic CVD process and involves CVD deposition of graphene on a sacrificial template (e.g. Ni foam). This graphene material follows the shape and dimensions of the Ni foam structure. The Ni foam is then etched away using an etchant, leaving behind a monolith of graphene framework, which is essentially an open cell foam. Useful references for this method include: 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 these methods: (a) catalytic CVD is inherently a very slow, highly energy-intensive and expensive method; (b) The etchant is typically a highly undesirable chemical and the resulting Ni-containing etching solution is a source of contamination. Recovering or recycling dissolved Ni metal from the etching solution is very difficult and expensive. (c) It is difficult to maintain the shape and dimensions of the graphene foam without damaging the cell walls when the Ni foam is etched away. The resulting graphene foam is typically very brittle and fragile. (d) Certain points within the sacrificial metal foam may be inaccessible to the CVD precursor gas, making it difficult to transport the CVD precursor gas (e.g., hydrocarbons) into the metal foam, resulting in a non-uniform structure.

A third method of making graphene foam also uses a self-assembly approach, using sacrificial metals (e.g., colloidal polystyrene particles, PS) coated with graphene oxide sheets. For example, Choi et al. prepared chemically modified graphene (CMG) paper in two steps: vacuum filtration of a mixed aqueous colloidal suspension of CMG and PS (2.0 μm PS spheres) to form free-standing PS/PS. A CMG film is prepared, and the PS beads are then removed to create 3D macro-pores [B. G. Choi, et al., "3D Macroporous Graphene Frameworks for Supercapacitors with High Energy and Power Densities," ACS Nano, 6 (2012) 4020-4028.] Choi et al. The preparation started by separately preparing the negatively charged CMG colloid and the positively charged PS suspension. The mixture of CMG colloid and PS suspension was dispersed in solution under controlled pH (=2), and both compounds had the same surface charge (zeta potential values of +13 ± 2.4 mV for CMG and +68 ± 5.6 mV for PS). had When the pH rises to 6, CMG (zeta potential = -29 ± 3.7 mV) and PS spheres (zeta potential = +51 ± 2.5 mV) come together due to their electrostatic interactions and hydrophobicity, which are then filtered. Through the process, it was integrated into PS/CMG composite paper. This method also has some drawbacks: (a) This method requires very demanding chemical treatment of both graphene oxide and PS particles. (b) Additionally, removal of PS with toluene results in weakening of the macroscopic porous structure. (c) Toluene is a highly regulated chemical and must be handled with great care. (d) The pore size is typically excessively large (e.g. several micrometers) and too large for many useful applications.

As discussed above, it is clear that all prior art methods or processes for producing graphene foam have major drawbacks. Therefore, the purpose of the present invention is to provide a cost-effective method for producing high-conductivity and mechanically strong graphene-based foams (specifically, integral 3D graphene-carbon hybrid foams) in large quantities. This method does not involve the use of environmentally unfriendly chemicals. This method allows flexible design and control of porosity level and pore size.

Another object of the present invention is to provide a method for producing graphene-carbon hybrid foams that exhibit thermal conductivity, electrical conductivity, elastic modulus, and/or strength equivalent to or greater than conventional graphite or carbon foams.

Another object of the present invention is to produce (a) a pure graphene-based hybrid foam comprising essentially all carbon, preferably with a meso-scaled pore size range (2-50 nm); and (b) non-pure graphene foam (graphene fluoride) comprising at least 0.001% by weight (typically 0.01% to 25% and most typically 0.1% to 20%) non-carbon elements, which can be used in a wide range of applications. , graphene chloride, graphene nitride, etc.).

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

The present invention provides a method for making integral 3D graphene-carbon hybrid foams directly from graphitic material particles and polymer particles. This method is surprisingly simple. This method:

(a) mixing multiple particles of a graphitic material and multiple particles of a solid polymeric carrier material to form a mixture in an impacting chamber of an energy impacting apparatus;

(b) operating this energy bombardment device for a long period of time at a frequency and intensity sufficient to exfoliate the graphene sheet from the graphitic material and move the graphene sheet to the surface of the solid polymer carrier material particle, thereby forming a graphene-coated or graphene -preparing the inserted polymer particles in an impact chamber; (For example, when the impact device is activated, it supplies kinetic energy to the polymer particles, which eventually impact the graphite particle surface/edge and exfoliate the graphene sheet from the impacted graphite particle. This exfoliated graphene sheet (This is referred to herein as a “direct transfer” process, meaning that the graphene sheets are moved directly from the graphite particles to the surface of the polymer particles without any third party intermediation.)

(c) recovering the graphene-coated or graphene-inserted polymer particles from the impact chamber and incorporating the graphene-coated or graphene-inserted polymer particles into a graphene-polymer hybrid structure of the desired shape (this integration The step can be as simple as a compression step that simply compresses the graphene-coated or embedded particles into the desired shape); and

(d) thermally decomposing this type of graphene-polymer composite structure to thermally convert the polymer into carbon or graphite that bonds the pores and graphene sheets to form an integrated 3D graphene-carbon hybrid foam.

In certain alternative embodiments, a plurality of impact balls or mediators are added to the impact chamber of the energy impact device. This impact ball, accelerated by an impact device, impacts the surface/edge of the graphite particle and exfoliates the graphene sheet therefrom. This graphene sheet is temporarily moved to the surface of this impact ball. This graphene-supported impact ball then impacts the polymer particle and moves the supported graphene sheet to the surface of this polymer particle. This series of events is referred to herein as the “indirect transfer” process. In some embodiments of the indirect transfer process, step (c) includes actuating a magnet to separate the impact ball or mediator from the graphene-coated or graphene-embedded polymer particles.

Particles of solid polymer material may include 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 or 200 μm. The solid polymer may be selected from solid particles of thermoplastics, thermosets, rubbers, semi-penetrating network polymers, penetrating network polymers, natural polymers, or combinations thereof. In one embodiment, the solid polymer is partially removed prior to step (d) by melting, etching, or dissolving in a solvent.

In certain embodiments, the graphitic material is natural graphite, synthetic graphite, highly oriented pyrolytic graphite, graphite fibers, graphite nanofibers, graphite fluoride, graphite oxide, chemically modified graphite, exfoliated graphite, recompressed exfoliation. selected from graphite, expanded graphite, mesocarbon microbeads, or combinations thereof. Preferably, the graphitic material comprises non-intercalated and non-oxidized graphitic material that has not been exposed to chemical or oxidizing treatments prior to mixing step (a).

The research group surprisingly observed that a wide variety of impact devices can be used to practice the present invention. For example, energy impact devices include vibrating ball mills, planetary ball mills, high energy mills, basket mills, agitator ball mills, cryo ball mills, micro ball mills, tumbler ball mills, and continuous ball mills. , stirred ball mill, pressurized ball mill, freezer mill, vibrating sieve, bead mill, nano bead mill, ultrasonic homogenizer mill, centrifugal planetary mixer, vacuum ball mill, or resonant acoustic mixer. It can be a mixer).

For the formation of the carbon component of the resulting graphene-carbon hybrid foam, polymer particles with a high carbon yield or char yield (e.g. greater than 30% by weight) can be selected. Carbon yield is the weight percent of the polymer structure that is thermally converted to a solid carbon phase rather than becoming part of the volatile gas. Polymers with high carbon yield include phenolic resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polybenzothiazole, It may be selected from polybenzobithiazole, poly(p-phenylene vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof.

When lower carbon content (higher graphene content) is desired in graphene-carbon hybrid foams, polymers include polyethylene, polypropylene, polybutylene, polyvinyl chloride, polycarbonate, acrylonitrile-butadiene (ABS), Polyester, polyvinyl alcohol, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene oxide (PPO), polymethyl methacrylate (PMMA), copolymers thereof, polymers thereof It may include low carbon yield polymers selected from blends, or combinations thereof.

It can be noted that when these polymers (both high and low carbon yield) are heated at temperatures between 300 and 2,500 degrees Celsius, they transform into carbon materials that nucleate preferentially near the edges of the graphene sheets. These carbon materials serve to bridge the gaps between graphene sheets, forming interconnected electronic conductive paths. In other words, the resulting graphene-carbon hybrid foam consists of an integrated 3D network structure of carbon-bonded graphene sheets, enabling continuous movement of electrons and phonons (quantized lattice vibrations) between graphene sheets or domains without interruption. . When further heated to temperatures above 2,500° C., the carbon phase that binds the graphene can become graphitized if the carbon phase is “soft carbon” or graphitizable. In this situation, both electronic and thermal conductivity are further increased.

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

It can be noted that thermal decomposition of polymers due to the generation of volatile gas molecules such as CO ₂ and H ₂ O tends to form pores within the resulting polymer carbon phase. However, these pores have a high tendency to collapse if not constrained when the polymer is carbonized. The research group surprisingly found that while graphene sheets wrapping around polymer particles can prevent the pore walls from shrinking and collapsing, some carbon species also penetrate the gaps between the graphene sheets and bind them together. did. The pore size and pore volume (porosity level) of the resulting 3D integral graphene foam depend on the starting polymer size and carbon yield of the polymer and, to a lesser extent, the pyrolysis temperature.

In certain preferred embodiments, the consolidation step includes compressing this large quantity of graphene-coated polymer particles into the desired shape. For example, a solid molded body can be easily formed by placing a large amount of graphene-coated particles in a mold cavity and pressing and compressing them. The polymer can be quickly heated and melted, the molded body slightly compressed to slightly fuse the polymer particles with each other by heat, and rapidly cooled to solidify the molded body. This consolidated body is then subjected to pyrolytic treatment (polymer carbonization and, optionally, graphitization).

In some alternative embodiments, the consolidation step includes melting the polymer particles to form a polymer melt mixture with graphene sheets dispersed therein, shaping the polymer melt mixture into a desired shape, and solidifying that shape into a graphene-polymer composite structure. It includes These forms may be rods, films (thin or thick, wide or narrow, single sheets or rolls), fibers (short filaments or continuous long filaments), plates, ingots, or any ordinary or unusual shape. Afterwards, this graphene-polymer composite form is thermally decomposed.

Alternatively, the consolidation step involves dissolving the polymer particles in a solvent to form a polymer solution mixture with graphene sheets dispersed therein, molding the polymer solution mixture into the desired shape, and removing the solvent to transform the shape into a graphene-polymer. It may include solidifying into a complex structure. This composite structure is then thermally decomposed to form a porous structure.

The consolidation step involves melting the polymer particles to form a polymer melt mixture with graphene sheets dispersed therein, extruding this mixture into rod or sheet form, spinning this mixture into fiber form, or grinding this mixture into powder form. This may include spraying or casting the mixture into an ingot form.

In some embodiments, the consolidation step includes dissolving the polymer particles in a solvent to form a polymer solution mixture with graphene sheets dispersed therein, extruding the solution mixture into a rod or sheet form, or extruding the solution mixture into a fiber form. This may include spinning, spraying the solution mixture into powder form, or casting the solution mixture into an ingot form and removing the solvent.

In certain embodiments, the polymer solution mixture is sprayed and then pyrolyzed (carbonized or carbonized and graphitized) to produce a graphene-polymer composite coating or film.

Preferably, the consolidation step involves compressing the graphene-coated polymer particles into a porous molded body with macroscopic pores, followed by adding petroleum pitch, coal tar pitch, aromatic organic materials (e.g. naphthalene or other pitch derivatives), monomers, organic polymers, Alternatively, it may include infiltrating or impregnating the pores with an additional carbon raw material selected from a combination thereof. Organic polymers include phenol resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polybenzothiazole, and polybenzovisti. It may include a high carbon yield polymer selected from azoles, poly(p-phenylene vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof. . When the molded body of impregnated graphene-coated polymer particles is thermally decomposed, this species becomes an additional carbon source when a higher amount of carbon is required in the hybrid foam.

Additionally, the present invention provides an integrated 3D graphene-carbon hybrid foam composed of multiple pores and pore walls, wherein the pore walls are chemically activated by a carbon material with a carbon material-to-graphene weight ratio of 1/200 to 1/2. Comprising bonded single-layer or few-layer graphene sheets, wherein the few-layer graphene sheets have 2 to 10 layers of overlapping graphene planes with an interplanar spacing d ₀₀₂ of 0.3354 nm to 0.36 nm as measured by X-ray diffraction, and a single The layered or few-layer graphene sheets may be made of pure graphene material with essentially 0% non-carbon elements or impure graphene material with 0.001% to 35% (preferably 0.01% to 25%) non-carbon elements by weight. This impure graphene includes graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, graphene nitride, and chemically functionalized graphene. is selected from graphene, or a combination thereof. A plurality of single-layer or few-layer graphene that accommodates the polymer particles in the lower layer can be overlapped with each other to form a stack of graphene sheets. These stacks may be greater than 5 nm in thickness, and in some cases greater than 10 nm, or even greater than 100 nm.

Integral 3D graphene-carbon hybrid foam typically has a density of 0.001 to 1.7 g/cm3 and a specific surface area of 50 to 3,000 m2/g. In a preferred embodiment, the pore walls comprise overlapping graphene planes with an interplanar spacing d ₀₀₂ between 0.3354 nm and 0.40 nm, as measured by X-ray diffraction.

For oil recovery devices (e.g. separating oil from water), the graphene-carbon is preferably 1 to 25% by weight (more preferably 1 to 15% and most preferably 1 to 10% by weight). %) of oxygen content. This can be achieved when the starting material is oxidized graphite, or when the carbonization treatment is performed in a mild oxidizing environment at a temperature of 300 to 1,500° C. (preferably 1,000° C. or lower) and no graphitization is performed thereafter. The research group surprisingly found that highly porous graphene-carbon foams with these properties can absorb up to 500% of their weight in oil from oil-water mixtures.

For thermal management applications, graphene-carbon hybrid foams are preferably prepared by subjecting carbon-bonded graphene sheets (after carbonization) to graphitization under compressive stress. This facilitates orientation and reorganization (merging, growth, etc.) of graphene sheets or graphene domains. As a result, the graphene-carbon foam sheet or film exhibits a thermal conductivity of at least 200 W/mK per unit specific gravity, and/or an electrical conductivity of at least 2,000 S/cm 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/cm3 or an average pore size of 2 nm to 50 nm. In one embodiment, the pore walls are made of graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, graphene nitride, chemically functionalized graphene. The solid graphene foam includes a non-pure graphene material selected from the group consisting of pins, and combinations thereof, and the solid graphene foam includes a non-carbon element content ranging from 0.01% to 20% by weight. That is, the non-carbon element may include an element selected from oxygen, fluorine, chlorine, bromine, iodine, nitrogen, hydrogen, or boron. In certain embodiments, the pore walls include graphene fluoride and the solid graphene foam includes a fluorine content of 0.01% to 20% by weight. In another embodiment, the pore walls include graphene oxide, and the solid graphene foam includes an oxygen content of 0.01% to 20% by weight. In one embodiment, the solid graphene-carbon hybrid foam has a specific surface area of 200 to 2,000 m2/g or a density of 0.01 to 1.5 g/cm3.

It can be noted that there are no restrictions on the shape or dimensions of the graphene-carbon hybrid foam of the present invention. In a preferred embodiment, the solid graphene-carbon hybrid foam has a thickness of at least 100 nm and not more than 10 cm and a length of at least 1 meter, preferably at least 2 meters, more preferably at least 10 meters, most preferably 100 meters. It is made in the form of roll sheets (rolls of continuous foam sheets) of continuous length. These sheet rolls are manufactured in a roll-to-roll process. There was no prior art regarding graphene-based foam made in sheet roll form. It has never been previously discovered or proposed that pure or impure-based continuous length graphene foams can be prepared by a roll-to-roll process.

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

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

In another preferred embodiment, the graphene-carbon hybrid foam has an oxygen content or a non-carbon content of less than 0.01% by weight, and the pore walls have an inter-graphene spacing of less than 0.336 nm and a mosaic spread value of less than 0.7. , a thermal conductivity of at least 350 W/mK per unit specific gravity, and/or an electrical conductivity of at least 3,500 S/cm per unit specific gravity.

In another preferred embodiment, the graphene foam has an inter-graphene spacing of less than 0.336 nm, a mosaic dispersion value of less than or equal to 0.4, a thermal conductivity of greater than 400 W/mK per unit of gravity, and/or greater than 4,000 S/cm per unit of gravity. It has pore walls containing overlapping graphene planes with electrical conductivity.

In a preferred embodiment, the pore walls comprise overlapping graphene planes with an inter-graphene spacing of less than 0.337 nm and a mosaic dispersion value of less than 1.0. In a preferred embodiment, the graphene foam exhibits a degree of graphitization of at least 80% (preferably at least 90%) and/or a mosaic dispersion value of less than 0.4. In a preferred embodiment, the pore walls comprise a 3D network of interconnected graphene planes.

In a preferred embodiment, the solid graphene-carbon hybrid foam comprises medium-sized pores with a pore size of 2 nm to 50 nm. Solid graphene foam can also be manufactured to contain micron-sized pores (1-500 ㎛).

The present invention also provides an oil-removing or oil-separating device comprising the 3D graphene-carbon hybrid foam of the present invention as an oil-absorbing element. Additionally, a solvent-removal or solvent-separation device comprising this 3D graphene-carbon hybrid foam as a solvent-absorbing element is provided.

The invention also provides a method for separating oil from oil-water mixtures (e.g., oil spills or wastewater from oil sands). The method includes the steps of (a) providing an oil-absorbing element comprising an integral graphene-carbon hybrid foam; (b) contacting the oil-water mixture with the element to absorb oil from the mixture; (c) withdrawing the urea from the mixture and extracting oil from the urea. Preferably, the method further comprises the step (d) of reusing said elements.

Additionally, the present invention provides a method for separating organic solvents from solvent-water mixtures or multiple-solvent mixtures. The method includes (a) providing an organic solvent-absorbent element comprising an integral graphene-carbon hybrid foam; (b) contacting the element with an organic solvent-water mixture or multi-solvent mixture comprising a first solvent and at least a second solvent; (c) allowing the element to absorb the organic solvent from the mixture or at least to absorb the first solvent from the second solvent; and (d) withdrawing the urea from the mixture and extracting the organic solvent or first solvent from the urea. Preferably, the method further comprises the step (e) of reusing said elements.

Figure 1 is a flow diagram illustrating the most commonly used prior art method for producing highly oxidized NGPs, which involves difficult chemical oxidation/embedding, cleaning, and high temperature exfoliation processes.
Figure 2a is a flow chart showing a method for manufacturing an integrated 3D graphene-carbon hybrid foam of the present invention.
Figure 2b is a schematic diagram showing the heat-induced conversion of polymer to carbon to bond graphene sheets together to form a 3D graphene-carbon hybrid foam. The compressed structure of graphene-coated polymer particles is converted into a highly porous structure.
Figure 3a is an SEM image of the internal structure of 3D graphene-carbon hybrid foam.
Figure 3b is an SEM image of the internal structure of another 3D graphene-carbon hybrid foam.
Figure 4A is a plot showing the thermal conductivity values versus specific gravity of 3D integral graphene-carbon foam, mesophasic pitch induced graphite foam, and Ni foam template assisted CVD graphene foam prepared by the method of the present invention.
Figure 4b is a chart showing the thermal conductivity values of 3D graphene-carbon foam and hydrothermally reduced GO graphene foam.
Figure 5 is a chart showing the thermal conductivity values of 3D graphene-carbon hybrid foam and pure graphene foam (made by casting with a blowing agent and then heat treatment) as a function of the final (maximum) heat treatment temperature.
Figure 6 is a chart showing the electrical conductivity values of 3D graphene-carbon foam and hydrothermally reduced GO graphene foam.
Figure 7 shows the amount of oil absorbed per gram of integral 3D graphene-carbon hybrid foam as a function of oxygen content in the foam with a porosity level of approximately 98% (separation of oil from oil-water mixture).
Figure 8 shows the amount of oil absorbed per gram of integral 3D graphene-carbon hybrid foam as a function of porosity level (with the same oxygen content).
Figure 9 shows the amount of chloroform absorbed in a chloroform-water mixture as a function of the degree of fluorination.
Figure 10 is a schematic diagram of a heat sink structure (two examples).

The present invention provides a method for producing integral 3D graphene-carbon hybrid foam directly from graphitic material particles and polymer particles.

As schematically shown in Figure 2A, the method begins by mixing multiple particles of graphitic material and multiple particles of a solid polymer carrier material to form a mixture, which is then passed through an energy impact device (e.g., a vibrating ball mill, Planetary ball mill, high energy mill, basket mill, agitator ball mill, cryogenic ball mill, micro ball mill, tumbler ball mill, continuous ball mill, stirred ball mill, pressurized ball mill, freeze mill, vibrating sieve, bead mill, nano It is placed within the impact chamber of a bead mill, ultrasonic homogenizer mill, centrifugal planetary agitator, vacuum ball mill, or resonant acoustic mixer). When in operation, this energy impact device imparts kinetic energy to the solid particles contained within it, causing the polymer particles to collide with the graphite particles at high intensity and frequency.

Under normal operating conditions, this impact causes the graphene sheets to delaminate from the graphitic material and move them to the surface of the solid polymer carrier material. These graphene sheets are wrapped around the polymer particles to form graphene-coated or graphene-embedded polymer particles within the impact chamber. This is referred to herein as a “direct transfer” process, meaning that the graphene sheets are transferred directly from the graphite particles to the surface of the polymer particles without any third party intermediation.

Alternatively, a plurality of impact balls or media may be added to the impact chamber of the energy impact device. Accelerated by an impact device, this impact ball has high kinetic energy and hits the surface/edge of the graphite particle at a good angle, thereby exfoliating the graphene sheet from the graphite particle. This graphene sheet is temporarily moved to the surface of this impact ball. This graphene-supported impact ball then collides with the polymer particle and moves this supported graphene sheet to the surface of this polymer particle. This series of events is referred to herein as the “indirect transfer” process. This event occurs with such a high frequency that most polymer particles are typically covered by graphene sheets in less than an hour. In some embodiments of the indirect transfer process, step (c) includes actuating a magnet to separate the impact ball or mediator from the graphene-coated or graphene-embedded polymer particles.

The method then involves recovering the graphene-coated or graphene-inserted polymer particles from the impact chamber and incorporating the graphene-coated or graphene-inserted polymer particles into a graphene-polymer composite structure of the desired shape. This integration step can be as simple as a compression step that simply mechanically compresses the graphene-coated or embedded particles into the desired shape. Alternatively, this consolidation step may involve melting the polymer particles to form a polymer matrix with graphene sheets dispersed therein. These graphene-polymer structures can be of any physical shape or dimension (fibers, rods, plates, cylinders, or any ordinary or unusual shape).

The graphene-polymer compact or composite structure is then thermally decomposed to thermally convert the polymer into carbon or graphite that bonds the graphene sheets, forming an integrated 3D graphene-carbon hybrid foam, as shown in Figures 3a and 3b. .

High carbon yield or char yield (e.g., greater than 30% by weight of the polymer converted to the solid carbon phase, instead of becoming part of the volatile gas) for the formation of the carbon component of the resulting graphene-carbon hybrid foam. You can select polymer particles having . Polymers with high carbon yield include phenolic resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, polybenzothiazole, It may be selected from polybenzobithiazole, poly(p-phenylene vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof. When thermally decomposed, the particles of these polymers become porous, as shown at the bottom of Figure 2b.

When lower carbon content (higher graphene relative to carbon ratio) and lower foam density are desired in graphene-carbon hybrid foams, polymers include polyethylene, polypropylene, polybutylene, polyvinyl chloride, polycarbonate, Acrylonitrile-butadiene (ABS), polyester, polyvinyl alcohol, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene oxide (PPO), polymethyl methacrylate (PMMA) , copolymers thereof, polymer blends thereof, or combinations thereof. When thermally decomposed, the particles of these polymers become porous, as shown in the middle of Figure 2b.

When these polymers (both high and low carbon yield) are heated at temperatures between 300 and 2,500 degrees Celsius, they transform into carbon materials that nucleate preferentially near the edges of the graphene sheets. These carbon materials naturally bridge the gaps between graphene sheets, forming interconnected electronically conductive pathways. In fact, the resulting graphene-carbon hybrid foam consists of an integrated 3D network of carbon-bonded graphene sheets, enabling continuous movement of electrons and phonons (quantized lattice vibrations) between graphene sheets or domains without interruption. . When further heated to temperatures higher than 2,500°C, the carbon phase can graphitize and further improve both electrical and thermal conductivity. When the graphitization time exceeds 1 hour, the amount of non-carbon elements is also typically reduced to less than 1% by weight.

It can be noted that organic polymers typically contain significant amounts of non-carbon elements, which can be reduced or removed through heat treatment. As such, thermal decomposition of polymers forms and releases volatile gas molecules such as CO ₂ and H ₂ O, resulting in the formation of pores on the resulting polymer carbon. However, these pores have a high tendency to collapse if not confined when the polymer is carbonized (the carbon structure can shrink as non-carbon elements are released). The research group surprisingly found that graphene sheets wrapped around polymer particles could prevent the pore walls from collapsing. Meanwhile, some carbon species also penetrate into the gaps between graphene sheets and bond them together. The pore size and pore volume (porosity level) of the resulting 3D monolithic graphene foam largely depend on the starting polymer size and the carbon yield of the polymer.

As raw materials for graphene sheets, graphite materials include natural graphite, synthetic graphite, highly oriented pyrolytic graphite, graphite fiber, graphite nanofiber, graphite fluoride, oxidized graphite, chemically modified graphite, exfoliated graphite, recompressed exfoliated graphite, and expanded It may be selected from graphite, mesocarbon microbeads, or combinations thereof. In this regard, there are several additional surprising elements associated with the method of the invention:

(1) Graphene sheets can be exfoliated from natural graphite using only polymer particles without using heavier and harder impact balls (e.g., zirconium dioxide or steel balls commonly used in ball mills). The exfoliated graphene sheet is moved directly to the surface of the polymer particle and tightly wraps around the polymer particle.

(2) It is also surprising that impact polymer particles can exfoliate graphene sheets from artificial graphites such as mesocarbon microbeads (MCMB), which are known to have an outer layer of amorphous carbon.

(3) With the help of harder impact balls, the graphene-like side of the carbon particles that constitute the internal structure of carbon or graphite fibers can also be exfoliated and transferred to the polymer particle surface. This has never been taught or suggested in the prior art.

(4) The present invention provides a surprisingly simple, fast, scalable, environmentally friendly, and cost-effective method, while fundamentally avoiding all the drawbacks associated with conventional processes for manufacturing graphene sheets. The graphene sheets are immediately transferred to the polymer particles, wrapped around them, and then easily converted into an integrated 3D graphene-carbon hybrid foam.

It can be noted that if the starting graphite is intentionally oxidized to some extent (e.g., to contain 2-15% oxygen by weight), the pore walls of the graphene-carbon hybrid foam can be imparted with a certain desired degree of hydrophilicity. there is. Alternatively, if the carbonization process is allowed to occur in a mildly oxidizing environment, oxygen-containing functional groups can be attached to the carbon. This feature can separate oil from water by selectively absorbing oil from the oil-water mixture. In other words, these graphene-carbon hybrid foam materials can recover oil from water, helping to clean up oil spilled rivers, lakes, or oceans. The oil absorption capacity is typically 50% to 500% of the foam's own weight. This is an extremely useful material for environmental protection purposes.

If high electrical or thermal conductivity is required, the graphitic material may be selected from non-intercalated and non-oxidized graphitic materials that have not been exposed to chemical or oxidizing treatments before being placed in the impact chamber. Alternatively or additionally, the graphene-carbon foam can be subjected to a graphitization treatment at temperatures higher than 2,500°C. The resulting material is particularly useful for thermal management applications (e.g., for the manufacture of finned heat sinks, heat exchangers, or heat spreaders).

It may be noted that the graphene-carbon foam may be compressed during and/or after the graphitization treatment. This process allows tuning the orientation and porosity of the graphene sheets.

X-ray diffraction patterns were obtained with an X-ray diffractometer equipped with CuKcv radiation. The shift and broadening of the diffraction peaks were corrected using silicon powder standards. The degree _of graphitization g _was calculated from the . This equation is valid only when d ₀₀₂ is approximately 0.3440 nm or less. Graphene foam walls with d ₀₀₂ greater than 0.3440 nm contain oxygen-containing or fluorine-containing functional groups (e.g., -F, OH, >O, and -COOH).

Another structural index that can be used to characterize the degree of alignment of overlapping and bonded graphene planes in the foam walls of graphene and conventional graphite crystals is the “mosaic spread”, which is (002) or (004) is expressed by the full width at half maximum of the rocking curve of the reflection (X-ray diffraction intensity). This degree of alignment characterizes the graphite or graphene crystal size (or grain size), amount of grain boundaries and other defects, and preferred crystal orientation. A nearly perfect single crystal of graphite is characterized by a mosaic dispersion value of 0.2 to 0.4. Most of the graphene walls of the present invention have a mosaic dispersion value in the range of 0.2 to 0.4 (when manufactured at a heat treatment temperature (HTT) of 2,500°C or higher). However, some values range from 0.4 to 0.7 for HTT between 1,500 and 2,500°C and from 0.7 to 1.0 for HTT between 300 and 1,500°C.

Close studies using a combination of SEM, TEM, limited field diffraction, indicates that it consists of >> 100 nm, often >> 1 μm, and in many cases >> 10 μm, or even >> 100 μm. These giant graphene planes overlap and bond along the thickness direction (c-crystal axis direction) when the final heat treatment temperature is below 2,500°C, often due to covalent bonding and not just van der Waals forces (as in conventional graphite microcrystals). It is also done by In this case, and without wishing to be limited by theory, Raman and FTIR spectroscopy studies indicate the ^{coexistence of sp 2 (} dominant) and sp ³ (weak but present) electron configurations, not just sp 2 as in conventional graphite.

The integral 3D graphene-carbon hybrid foam is composed of multiple pores and pore walls, the pore walls being a single layer or few layers chemically bonded by carbon material with a carbon material-to-graphene weight ratio of 1/100 to 1/2. Comprising a graphene sheet, the few-layer graphene sheet has 2 to 10 layers of overlapping graphene planes having an interplanar spacing d ₀₀₂ of 0.3354 nm to 0.36 nm as measured by X-ray diffraction, and is a single-layer or few-layer graphene sheet. includes pure graphene material with essentially 0% non-carbon elements or impure graphene material with 0.01% to 25% (more typically less than 15%) non-carbon elements by weight, impure graphene From silver graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, graphene nitride, chemically functionalized graphene, or combinations thereof. is selected. A plurality of single-layer or few-layer graphene that accommodates the polymer particles in the lower layer can be overlapped with each other to form a stack of graphene sheets. These stacks may be greater than 5 nm thick, and in some cases greater than 10 nm, or even greater than 100 nm.

The integral 3D graphene-carbon hybrid foam typically has a density of 0.001 to 1.7 g/cm3, a specific surface area of 50 to 3,000 m2/g, a thermal conductivity of at least 200 W/mK per unit specific gravity, and/or 2,000 S per unit specific gravity. It has an electrical conductivity of more than /cm. In a preferred embodiment, the pore walls comprise overlapping graphene planes with an interplanar spacing d ₀₀₂ between 0.3354 nm and 0.40 nm, as measured by X-ray diffraction.

Multiple graphene sheets can be merged into one integrated graphene object through covalent bonds between their edges. The gaps between the free ends of the unmerged sheets or shorter merged sheets are joined by carbon phases converted from the polymer. These unique chemical compositions (including oxygen or fluorine content, etc.), morphology, crystal structure (including inter-graphene spacing), and structural characteristics (e.g., degree of alignment, near absence of defects, chemical bonds, and Due to the absence of gaps and substantially no breaks along the direction of the graphene face, graphene-carbon hybrid foams have a unique combination of excellent thermal conductivity, electrical conductivity, mechanical strength and stiffness (elastic modulus).

Thermal management applications

The aforementioned features and properties make monolithic 3D graphene-carbon hybrid foams ideal for a wide range of engineering and biomedical applications. For example, for thermal management purposes only, graphene-carbon foam can be used for:

a) Graphene-carbon hybrid foam, with its compressibility and high thermal conductivity, is ideally suited for use as a thermal interface material (TIM) that can be implemented between a heat source and a heat spreader or between a heat source and a heat sink. do.

b) Hybrid foam can be used as a heat spreader by itself due to its high thermal conductivity.

c) Hybrid foams can be used as heat sinks or heat dissipation materials due to their high heat diffusion ability (high thermal conductivity) and high heat dissipation ability (multiple surface pores leading to massive air convection micro or nano channels).

d) Light weight (low density adjustable from 0.001 to 1.8 g/cm3), high thermal conductivity per unit specific gravity or per unit physical density, and high structural integrity (graphene sheets bonded by carbon) make this hybrid foam durable. This makes it an ideal material for heat exchangers.

Graphene-carbon hybrid foam-based thermal management devices or heat dissipation devices include heat exchangers, heat sinks (e.g., finned heat sinks), heat pipes, high-conductivity inserts, and thin or thick heat sinks (between the heat sink and the heat source). It includes conductive plates, heat transfer media (or heat transfer materials, TIM), or thermoelectric or Peltier cooling plates.

A heat exchanger is a device used to transfer heat between one or more fluids (e.g., a gas and a liquid flowing separately in different channels). Fluids are typically separated by solid walls that prevent mixing. The graphene-carbon hybrid foam material of the present invention is an ideal material for such walls unless the foam is a completely open cell foam capable of mixing fluids. The method of the present invention can produce both open-cell and closed-cell foam structures. The large surface pore area allows for dramatically faster heat exchange between two fluids or multiple fluids.

Heat exchangers are widely used in refrigeration systems, air conditioning units, heaters, power plants, chemical plants, petrochemical plants, oil refineries, natural gas processing, and sewage treatment. A well-known example of a heat exchanger is found in internal combustion engines, where circulating engine coolant flows through radiator coils while air flows past these coils, cooling the coolant and heating the incoming air. Solid walls (which make up radiator coils, for example) are usually made of high thermal conductivity materials such as Cu and Al. The graphene foam of the present invention with higher thermal conductivity or higher specific surface area is an excellent substitute for Cu and Al, for example.

There are many types of heat exchangers commercially available: shell and tube heat exchanger, plate and shell heat exchanger, and adiabatic wheel heat exchanger. ), plate fin heat exchanger, pillow plate heat exchanger, fluid heat exchanger, waste heat recovery unit, dynamic scraped surface heat exchanger, phase change heat exchanger, Direct contact heat exchanger, and micro-channel heat exchanger. Both of these types of heat exchangers can utilize the very high thermal conductivity and specific surface area of the foam material of the invention.

The solid graphene foam of the present invention can also be used in heat sinks. Heat sinks are widely used in electronic devices for heat dissipation purposes. In portable small electronic devices (e.g. laptop computers, tablets and smartphones), central processing units (CPUs) and batteries are well-known heat sources. Typically, a metallic or graphite object (e.g. Cu foil or graphite foil) is brought into contact with a hot surface and this object spreads heat to the outer surface or to the outside air (mainly by conduction and convection and to a lesser extent by radiation). helps to do In most cases, a thin thermal transfer material (TIM) transfers heat between the hot surface of the heat source and the heat spreading surface of the heat spreader or heat sink.

Heat sinks usually consist of a structure of highly conductive material with one or more flat surfaces to ensure good thermal contact with the components to be cooled, and comb- or fin-shaped protrusions to increase surface contact with air and thereby speed up heat dissipation. . Heat sinks can be used with fans to increase air flow above the heat sink. Heat sinks may have multiple fins (extended or raised surfaces) to enhance heat transfer. In electronic devices with limited space, the shape/arrangement of the fins must be optimized to maximize heat transfer density. Alternatively or additionally, a cavity (inverted fin) may be inserted in the area formed between adjacent fins. These cavities are effective in extracting heat from various heating elements to the heat sink.

Typically, an integrated heat sink includes a heat collection member (core or base) and at least one heat dissipation member (e.g., one fin or multiple fins) built into the heat collection member (base), creating a fin-type heat sink. form Rather than applying external adhesive or using mechanical fastening means to connect the pin to the core, the pin and core are naturally connected or integrated with each other to form an integrated body. The heat collection base has a surface in thermal contact with a heat source (eg, an LED), collects heat from the heat source, and dissipates it into the air through the fins.

As an illustrative example, Figure 10 provides a schematic diagram of two heat sinks 300 and 302 . The first heat sink includes a heat collection member (or base member) 304 and a plurality of fins or heat dissipation members (e.g., fins 306 ) connected to the base member 304 . Base member 304 is shown having a heat collection surface 314 for thermal contact with a heat source. The heat dissipating member or fin 306 is shown as having at least a heat dissipating surface 320 .

A particularly useful embodiment includes (a) a base ( 308 ) comprising a heat collection surface ( 318 ); and (b) a radially finned heat sink assembly comprising a plurality of spaced apart parallel planar fin members (e.g., 310, 312 as two examples) integral with or supported by the base 308 . An integrated radial heat sink 302 comprising a planar fin member (e.g. 310 ) comprising at least one heat dissipating surface 322 . Preferably a plurality of parallel planar fin members are equally spaced.

The graphene-carbon hybrid foam of the present invention, which has high elasticity and resilience, is itself a good heat transfer material and is also a highly efficient heat diffusion element. Additionally, this highly conductive foam can be used as inserts for electronic cooling and to enhance heat removal from small chips to heat sinks. Since the space occupied by high-conductivity materials is important, a more efficient design is to use high-conductivity passages that can be inserted into the heating element. The elastic, highly conductive solid graphene foam disclosed herein perfectly satisfies these needs.

Due to its high elasticity and high thermal conductivity, the solid graphene-carbon hybrid foam of the present invention becomes a highly conductive thick plate that lies as a heat transfer interface between the heat source and the cooling flow fluid (or other heat sink), improving cooling performance. . In this arrangement, the heat source is cooled under a thick graphene foam plate instead of being cooled in direct contact with the cooling fluid. Thick sheets of graphene foam can significantly improve heat transfer between a heat source and a cooling fluid by transferring heat flow in an optimal manner. No additional pumping power or additional heat transfer surface area is required.

Additionally, solid graphene foam is an excellent material for constructing heat pipes. A heat pipe is a heat transfer device that transfers a large amount of heat with a very small temperature difference between a hot and cold interface by using the evaporation and condensation of a fluid or coolant that operates in two phases. A conventional heat pipe consists of a sealed hollow tube made of a thermally conductive material such as Cu or Al, and a wick that returns the working fluid from the evaporator to the condenser. The pipe contains both the vapor and saturated liquid of the working fluid (such as water, methanol, or ammonia) and blocks all other gases. However, both Cu and Al are prone to oxidation or corrosion, so their performance deteriorates relatively quickly over time. On the other hand, solid graphene foam is chemically inert and has no problems with oxidation or corrosion. Heat pipes for electronic thermal management can have a shell and wick made of solid graphene foam, with water as the working fluid. Graphene/methanol can be used if heat pipes need to operate below the freezing point of water, and graphene/ammonia heat pipes can be used for cooling electronics in space.

Peltier cold plates work on the Peltier effect, which creates a heat flux between the junction of two different electrical conductors by applying an electric current. This effect is commonly used to cool electronic components and small devices. In fact, many of these joints can be arranged in series to enhance this effect up to the required amount of heating or cooling. This solid graphene foam can be used to improve heat transfer efficiency.

Filtration and fluid absorption applications

Solid graphene foams can be prepared to contain micropores (less than 2 nm) or medium-sized pores with a pore size of 2 nm to 5 nm. Solid graphene-carbon hybrid foams can also be prepared to contain micron-sized pores (1-500 μm). With well-controlled pore size alone, the graphene-carbon foam of the present invention can be an excellent filter material for air or water filtration.

Additionally, the chemistry of the graphene pore walls and the carbon phase (e.g., as reflected by the % of O, F, N, H, etc. in the foam) can be influenced by either or both the graphene sheets and the carbon binder phase. can be independently controlled to impart different amounts of functional groups and/or different types of functional groups. This means that both pore size and chemical functional groups can be controlled simultaneously or separately at different positions in the internal structure, resulting in many unexpected properties, synergistic effects, and some unique combinations of properties that are usually considered mutually exclusive (e.g., some parts of the structure are hydrophobic). It provides the highest degree of freedom or unprecedented flexibility to design and fabricate graphene-carbon hybrid foams (where the other parts are hydrophilic or when the foam structure has both hydrophobic and lipophilic properties). If water does not penetrate a material or surface, such surface or material is said to be hydrophobic and water droplets placed on the hydrophobic surface or material will form a large contact angle. When a surface or substance is lipophilic, it means that it has a strong affinity for oil, not water. The method of the present invention allows precise control of hydrophobicity, hydrophilicity, and lipophilicity.

The present invention also provides an oil-removal, oil-separation, or oil-recovery device comprising the 3D graphene-carbon hybrid foam of the present invention as an oil-absorbing element or oil-separating element. Additionally, a solvent-removal or solvent-separation device comprising a 3D graphene-carbon hybrid foam as a solvent-absorbing element is provided.

The main advantage of using the graphene-carbon hybrid foam of the present invention as an oil-absorbing element lies in its structural integrity. Due to the concept that the graphene sheets are chemically bonded by carbon materials, the resulting foam does not decompose during repeated oil absorption operations. On the other hand, our research group found that graphene-based oil-absorbing elements prepared by hydrothermal reduction, vacuum-assisted filtration, or freeze-drying decomposed after two or three oil absorptions. There is nothing (except the weak van der Waals forces that exist before initial contact with oil) to hold these otherwise separate graphene sheets together. Once these graphene sheets become wet with oil, they can no longer return to their original form as oil-absorbing elements.

Another key advantage of this technology is the ability to design and manufacture oil-absorbing elements that can absorb up to 400 times their weight in oil while still maintaining the structural shape of the oil-absorbing element (without significantly expanding). It's flexibility. The amount of oil absorption depends on the specific pore volume of the foam, which can be mainly controlled by the ratio between the amount of graphene sheets and the amount of original carrier polymer particles before heat treatment.

Additionally, the present invention provides a method for separating/recovering oil from oil-water mixtures (e.g., oil spills or wastewater from oil sands). The method includes the steps of (a) providing an oil-absorbing element comprising an integral graphene-carbon hybrid foam; (b) contacting the oil-water mixture with the element to absorb oil from the mixture; (c) removing the oil-absorbing element from the mixture and extracting oil from the element. Preferably, the method further comprises the step (d) of reusing said elements.

Additionally, a method for separating organic solvents from solvent-water mixtures or multi-solvent mixtures is provided. The method includes (a) providing an organic solvent-absorbing element comprising an integral graphene-carbon hybrid foam; (b) contacting the element with an organic solvent-water mixture or multi-solvent mixture comprising a first solvent and at least a second solvent; (c) allowing the element to absorb the organic solvent from the mixture or at least to absorb the first solvent from the second solvent; and (d) withdrawing the urea from the mixture and extracting the organic solvent or first solvent from the urea. Preferably, the method further comprises the step (e) of reusing the solvent-absorbing element.

The following examples are used as examples to detail the best mode for carrying out the invention and should not be construed as limiting the scope of the invention.

Example 1 : Preparation of graphene-carbon foam from flake graphite via polypropylene powder-based solid polymer carrier

In the experiment, 1 kg of polypropylene (PP) pellets, 50 grams of flake graphite, 50 mesh (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 vessel. The ball mill was operated at 300 rpm for 2 hours. The container lid was removed and the stainless steel ball was removed via a magnet. It was confirmed that the polymer carrier material was coated with a dark graphene layer. The carrier material was placed on a 50 mesh sieve to remove a small amount of untreated flake graphite.

Then, a sample of the coated carrier material was immersed in tetrachloroethylene at 80°C for 24 hours to dissolve the PP and allow the graphene sheets to disperse in the organic solvent. After solvent removal, independent graphene sheet powder was recovered (mostly few-layer graphene). Afterwards, the remaining coated carrier material was compressed in the mold cavity to form a molded body, and then heat-treated at 350°C in a sealed crucible and then at 600°C for 2 hours to produce a graphene-carbon foam. .

In a separate experiment, identical batches of PP pellets and flake graphite particles (without impact steel balls) were placed in the same high energy ball mill vessel and the ball mill was run under the same conditions for the same amount of time. The results were compared to those obtained from impact ball-assisted operation. When PP is dissolved, the graphene sheets that are independent from the PP particles are mostly single-layer graphene. Graphene-carbon foams prepared by this method have a higher level of porosity (lower physical density).

Although polypropylene (PP) is used as an example herein, the carrier material for producing graphene-carbon hybrid foam is not limited to PP. Any polymer that can be manufactured in the form of fine particles (thermoplastic resin, thermosetting resin, rubber, wax, mastic resin, gum, organic resin, etc.) can be used. It may be noted that uncured or partially cured thermosets (e.g. epoxide and imide-based oligomers or rubbers) can be prepared in particle form below room temperature (e.g. cryogenic temperatures). Therefore, partially cured thermosetting resin particles can also be used as polymer carriers.

Example 2 : Graphene-carbon hybrid foam using expanded graphite (thickness greater than 100 nm) as graphene raw material and ABS as polymer solid carrier particles.

In the experiment, 100 grams of ABS pellets as solid carrier material particles were placed in a 16 ounce plastic container along with 5 grams of expanded graphite. This container was placed in an acoustic mixer (Resodyn Acoustic mixer) and treated for 30 minutes. After treatment, it was confirmed that the carrier material was coated with a thin carbon layer. A small sample of the carrier material was placed in acetone and ultrasonic energy was applied to accelerate the dissolution of ABS. The solution was filtered through an appropriate 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. This sample was examined with an optical microscope and confirmed to be graphene. The remaining pellets were extruded to create graphene-polymer sheets (1 mm thick) and then carbonized to prepare graphene-carbon foam samples under different temperatures and compression conditions.

Example 3 : Preparation of graphene-carbon hybrid foam from mesocarbon microbeads (MCMB, graphene raw material) and polyacrylonitrile (PAN) fibers (solid carrier particles)

In one embodiment, 100 grams of PAN fiber segments (2 mm long as carrier particles), 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. did. After the treatment was completed, the vibrating mill was opened to confirm that the carrier material was coated with a dark coating of graphene sheets. Zirconia particles with distinctly different sizes and colors were removed manually. The graphene-coated PAN fibers were then compressed and melted together to form several composite films. The film was heat treated at 250°C for 1 hour (in room air), 350°C for 2 hours, and 1,000°C for 2 hours (under argon gas atmosphere) to obtain a graphene-carbon foam layer. Half of the carbonized foam layer was then heated to 2,850° C. and held at this temperature for 0.5 hours.

Example 4 : Phenolic resin particles cured as polymer carrier material in a freeze mill

In one experiment, 10 grams of phenolic resin particles were placed in a SPEX mill sample holder (SPEX Sample Prep, Metzkin, NJ) along with 0.25 grams of HOPG powder derived from graphitized polyimide and a magnetic stainless steel impactor. The same experiment was performed, but the sample holder did not contain any impactor balls. This process was performed in a “dry room” at 1% humidity to reduce water condensation on the finished product. The SPEX mill was run for 10-120 minutes. After operation, the contents of the sample holder were sorted and the HOPG powder residue and impactor ball (when used) were removed to recover the graphene-coated resin particles.

In both cases (with and without impactor balls), the resulting graphene-coated resin particles were examined using both digital optical microscopy and scanning electron microscopy (SEM). It was observed that the thickness of the graphene sheet wrapping around the resin particle increased with milling run time, and for a given same run time, impactor-assisted run resulted in a thicker graphene coating.

A large amount of graphene-coated resin particles were compressed to form a molded body and then infiltrated with a small amount of petroleum pitch. Separately, other molded bodies of graphene-coated resin particles were prepared under similar conditions, but pitch penetration was not attempted. Afterwards, the two molded bodies were subjected to the same pyrolysis treatment.

Example 5 : Natural graphite particles as graphene raw material, polyethylene (PE) or nylon 6/6 beads as solid carrier particles, and ceramic or glass beads as added impact balls.

In the experiment, 0.5 kg of PE or nylon beads (as solid carrier material), 50 grams of natural graphite (graphene sheet raw material), and 250 grams of zirconia powder (impact balls) were placed in the container of a planetary ball mill. The ball mill was operated at 300 rpm for 4 hours. The container lid was removed and the zirconia beads (different size and weight than the graphene-coated PE beads) were removed through a vibrating screen. It was confirmed that the polymer carrier material particles were coated with a dark graphene layer. The carrier material was placed on a 50 mesh sieve to remove a small amount of raw flake graphite. In a separate experiment, glass beads were used as impact balls; Other ball-milling operating conditions were kept the same.

A large amount of graphene-coated PE pellets and a large amount of graphene-coated nylon beads were each compressed in a mold cavity, briefly heated above the melting point of PE or nylon, and then rapidly cooled to form two molded bodies. For comparison, two corresponding molded bodies were prepared from a quantity of uncoated PE pellets and a quantity of uncoated nylon beads. Afterwards, these four molded bodies were pyrolyzed (by heating the molded bodies in a chamber from 100°C to 650°C). The results were very surprising. It was confirmed that the molded body of graphene-coated polymer particles was converted into a graphene-carbon hybrid foam structure with dimensions similar to the dimensions of the original molded body (3 cm x 3 cm x 0.5 cm). As a result of examining this structure using SEM, it was found that a carbon phase exists near the edge of the graphene sheet and that this carbon phase plays a role in bonding the graphene sheets to each other. As schematically shown in Figure 2A, carbon-bonded graphene sheets form the framework of graphene-carbon hybrid pore walls with pores existing where the spaces originally occupied by the polymer particles.

On the other hand, the two green bodies obtained from the uncoated pellets or beads shrunk into essentially two solid lumps of carbon with a volume of approximately 15% to 20% of the original green body volume. This highly contracted solid mass is a substantially pore-free carbon material; This is not a foam material.

Example 6 : Micron-sized rubber particles as solid polymer carrier particles

The experiment began with the preparation of micron-sized rubber particles. A mixture of methylhydro dimethyl-siloxane polymer (20 g) and polydimethylsiloxane, vinyldimethyl terminated polymer (30 g) was obtained using a homogenizer for 1 minute under atmospheric conditions. Tween 80 (4.6 g) was added and the mixture was homogenized for 20 seconds. Platinum-divinyltetramethyldisiloxane complex (0.5 g in 15 g methanol) was added and mixed for 10 seconds. This mixture was added to 350 g of distilled water and homogenized for 15 minutes to obtain stable latex. This latex was heated to 60°C for 15 hours. This latex was then demulsified with anhydrous sodium sulfate (20 g), filtered under vacuum, washed with distilled water and dried under vacuum at 25°C to obtain silicone rubber particles. The particle size distribution of the produced rubber particles was 3 to 11 ㎛.

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 completing the treatment, the vibrating mill was opened and it was confirmed that the rubber particles were coated with a dark coating of graphene sheets. Zirconia particles were removed manually. The graphene-coated rubber particles were then mixed with 5% by weight petroleum pitch (as a binder) and mechanically compressed together to form several composite sheets. Then, the composite sheet was heat treated in a tubular furnace at 350°C for 1 hour, 650°C for 2 hours, and 1,000°C for 1 hour to obtain a graphene-carbon foam layer.

Example 7 : Preparation of graphene fluoride foam

In a conventional method, the graphene-carbon hybrid sheet was fluorinated with vapor of chlorine trifluoride in a sealed autoclave reactor to obtain a fluorinated graphene-carbon hybrid film. To achieve various degrees of discord, the duration of discord was varied. The fluorinated graphene-carbon foam sheets were then individually immersed in each container containing the chloroform-water mixture. This foam sheet selectively absorbed chloroform from water, and the amount of absorbed chloroform was observed to increase with the degree of fluorination until the fluorine content reached 7.3% by weight (FIG. 9).

Example 8 : Preparation of graphene oxide foam and graphene nitride foam

Several graphene-carbon foams prepared in Example 3 were immersed in a 30% H ₂ O ₂ -water solution for 2 to 48 hours to obtain graphene oxide (GO) foams with an oxygen content of 2 to 25% by weight. .

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

It can be noted that the different functionalization treatments of the graphene-carbon hybrid foam are for different purposes. For example, oxidized graphene-carbon hybrid foam structures are particularly effective as oil absorbents from oil-water mixtures (i.e., oil poured on water and mixed together). In this case, the integral 3D graphene (oxygen 0-15 wt%)-carbon foam structure is both hydrophobic and lipophilic (Figures 7 and 8). If water does not penetrate a material or surface, such surface or material is said to be hydrophobic and water droplets placed on the hydrophobic surface or material will form a large contact angle. When a surface or substance is lipophilic, it means that it has a strong affinity for oil, not water.

Additionally, different contents of O, F, and/or N enable the graphene-carbon hybrid foam of the present invention to absorb several organic solvents from water or to separate one organic solvent from a mixture of multiple solvents. .

Comparative Example 1 : Carbonization of graphene and graphene-polymer composite through Hummer's Process

Graphite oxide was prepared by oxidizing graphite flakes with sulfuric acid, nitrate, and permanganate following the method of Hummers [US Patent No. 2,798,878, July 9, 1957]. As soon as the reaction was complete, the mixture was poured into deionized water and filtered. Graphite oxide was washed repeatedly in 5% HCl solution to remove most of the sulfate ions. The sample was then washed repeatedly with deionized water until the pH of the filtrate became neutral. The slurry was spray dried and stored in a vacuum oven at 60°C for 24 hours. The interlayer spacing of the resulting layered graphite oxide was measured to be about 0.73 nm (7.3 A) by Debey-Scherrer X-ray technique. A sample of this material was then transferred to a preset furnace, exfoliated at 650°C for 4 minutes, and heated at 1200°C for 4 hours in an inert atmosphere furnace to produce a low-density powder composed of few-layer reduced graphene oxide (RGO). created. Surface area was measured via nitrogen absorption BET. This powder was then dry mixed with ABS, PE, PP, and nylon pellets at a loading level of 1% to 25%, respectively, and blended using a 25 mm twin-screw extruder to form a composite sheet. This composite sheet was then thermally decomposed.

Comparative Example 2 : Preparation of single-layer graphene oxide (GO) sheets from mesocarbon microbeads (MCMB) followed by preparation of graphene foam layers from GO sheets.

Mesocarbon microbeads (MCMB) were supplied from China Steel Chemical Co., Kaohsiung, Taiwan. This material has a density of about 2.24 g/cm3 and a median particle size of about 16 μm. MCMB (10 grams) was introduced into an acid solution (4:1:0.05 ratio of sulfuric acid, nitric acid, and potassium permanganate) for 48 to 96 hours. Once the reaction was complete, the mixture was poured into deionized water and filtered. The inserted MCMB was washed repeatedly in 5% HCl solution to remove most of the sulfate ions. The sample was then washed repeatedly with deionized water until the pH of the filtrate was above 4.5. The slurry was then sonicated for 10 to 100 min to prepare a GO suspension. TEM and atomic force microscopy studies suggest that when the oxidation treatment exceeded 72 hours, most of the GO sheets were single-layer graphene, and when the oxidation time was 48 to 72 hours, most of the GO sheets were two- or three-layer graphene.

The GO sheets contain an oxygen proportion of approximately 35% to 47% by weight during the oxidation treatment time of 48 to 96 hours. GO sheets were suspended in water. Baking soda (5-20% by weight) as a chemical foaming agent was added to the suspension immediately before casting. This suspension was then cast onto a glass surface. Several samples were cast, some with blowing agent and some without. The resulting GO film, after removing the liquid, can vary in thickness from approximately 10 to 500 μm. Next, several sheets of GO films with or without a foaming agent were heat treated at a heating temperature of 80 to 500°C for 1 to 5 hours to create a graphene foam structure.

Comparative Example 3 : Preparation of pure graphene foam (0% oxygen)

Recognizing the possibility of a high number of defects in GO sheets acting to reduce the conductivity of individual graphene planes, the use of pure graphene sheets (non-oxidized and oxygen-free, non-halogenated and halogen-free, etc.) It was decided to study whether this could lead to graphene foams with higher thermal conductivity. Pure graphene sheets were prepared using a direct sonication process (known in the art as liquid-phase exfoliation).

In a conventional method, 5 g of graphite flakes ground to a size of approximately 20 μm or less were dispersed in 1,000 mL of deionized water (containing 0.1% by weight of the dispersing agent, Zonyl® FSO from DuPont) to obtain a suspension. The graphene sheets were exfoliated, separated, and reduced in size using an ultrasonic energy level of 85 W (Branson S450 sonicator) over a period of 15 minutes to 2 hours. The resulting graphene sheets are pure graphene that has not been oxidized, is oxygen-free, and is relatively defect-free. Pure graphene does not contain any non-carbon elements.

Various amounts (1% to 30% by weight relative to the graphene material) of chemical blowing agents (N,N-dinitroso pentamethylene tetramine or 4,4'-oxybis(benzenesulfonyl hydrazide)) were added in pure water. It was added to the suspension containing the graphene sheet and surfactant. This suspension was then cast onto a glass surface. Several samples were cast, one prepared by injecting CO ₂ as a physical blowing agent into the suspension immediately before casting. The resulting graphene film, after removing the liquid, may vary in thickness from approximately 10 to 100 ㎛. Next, the graphene film was heat treated at a temperature of 80 to 1,500°C for 1 to 5 hours to produce a graphene foam.

Comparative Example 4 : CVD graphene foam on Ni foam template

This method is described in published literature [Chen, Z. et al. “Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapor deposition,” Nat. Mater. 10, 424-428 (2011). Nickel foam, a porous structure with an interconnected 3D scaffold of nickel, 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 normal pressure, and then a graphene film was deposited on the surface of the nickel foam. Due to the difference in thermal expansion coefficient between nickel and graphene, ripples and wrinkles formed on the graphene film. To recover (separate) the graphene foam, the Ni frame must be etched away. Before etching away the nickel framework with hot HCl (or FeCl ₃ ) solution, poly(methyl methacrylate) (PMMA) was applied on the surface of the graphene film as a support to prevent collapse of the graphene network during nickel etching. A thin layer of was deposited. The PMMA layer was carefully removed with hot acetone and a weak graphene foam sample was obtained. The use of a PMMA support layer is important to fabricate free-standing films of graphene foam; Without the PMMA support layer, only highly distorted and deformed graphene foam samples were obtained. This is a difficult process that is not environmentally friendly and has no scalability.

Comparative Example 5 : Conventional graphite foam from pitch-based carbon foam

The pitch powder, granules, or pellets are placed into an aluminum mold with the desired final shape of the foam. Mitsubishi ARA-24 mesophase pitch was used. The sample was evacuated to less than 1 torr and then heated to a temperature of approximately 300°C. At this point, the vacuum was released with a nitrogen blanket and then pressure up to 1,000 psi was applied. The temperature of the system was then raised to 800°C. This was performed at a rate of 2°C/min. Maintain this temperature for at least 15 minutes to achieve a soak, then turn off furnace power and cool to room temperature at approximately 1.5°C/min while releasing pressure at approximately 2 psi/min. I ordered it. Final foam temperatures were 630°C and 800°C. During the cooling cycle, the pressure was gradually released to atmospheric conditions. The foam was then heat treated to 1050°C under a nitrogen blanket (carbonization) and then in separate runs to 2500°C and 2800°C in a graphite crucible under argon (graphitization).

Comparative Example 6 : Graphene foam from hydrothermally reduced graphene oxide

For comparison, self-assembled graphene hydrogel (SGH) samples were prepared by a one-step hydrothermal method. In a conventional method, SGH can be easily prepared by heating 2 mg/mL of a sealed homogeneous graphene oxide (GO) aqueous dispersion to 180°C for 12 hours in a Teflon-lined autoclave. SGH, which contains approximately 2.6% by weight graphene sheets and 97.4% water, has an electrical conductivity of approximately 5 x 10 ^-3 S/cm. Upon drying and heat treatment at 1,500°C, the resulting graphene foam exhibits an electrical conductivity of approximately 1.5 x 10 ^-1 S/cm, which is two times lower than that of the graphene foam of the present invention prepared by heat treatment at the same temperature. .

Example 9 : Thermal and mechanical testing of various graphene foams and conventional graphite foams

Samples of various conventional carbon or graphene foam materials were processed into specimens for thermal conductivity measurements. The bulk thermal conductivity of the mesophasic pitch induced foam ranged from 67 W/mK to 151 W/mK. The density of the samples was 0.31 to 0.61 g/cm3. Considering the weight, the specific thermal conductivity of the pitch derived foam is approximately 67/0.31 = 216 and 151/0.61 = 247.5 W/mK per specific gravity (or physical density).

The compressive strength of the sample with an average density of 0.51 g/cm3 was measured at 3.6 MPa, and the compressive modulus was measured at 74 MPa. In contrast, the compressive strength and compressive modulus of the inventive graphene-carbon foam sample with similar physical density are 6.2 MPa and 113 MPa, respectively.

Figure 4a shows the thermal conductivity values versus specific gravity of 3D integral graphene-carbon foam, mesophasic pitch induced graphite foam, and Ni foam template assisted CVD graphene foam. This data clearly explains the following unexpected results:

1) The 3D integral graphene-carbon foam prepared by the method of the present invention exhibits significantly higher thermal conductivity compared to mesophase pitch-induced graphite foam and Ni foam template-assisted CVD graphene, given the same physical density.

2) This is very surprising, considering that CVD graphene is essentially pure graphene that has never been exposed to oxidation, and should have exhibited higher thermal conductivity compared to the graphene-carbon hybrid foam of the present invention. The carbon phase of hybrid foams is generally less crystalline (some is amorphous carbon) and therefore has much lower thermal or electrical conductivity than graphene alone. However, when the carbon phase is combined with graphene sheets to form an integrated structure prepared by the method of the present invention, the resulting hybrid foam exhibits a thermal conductivity similar to that of completely pure graphene foam. These very high thermal conductivity values observed in the graphene-carbon hybrid foam prepared here are surprising. This is likely due to the observation that the otherwise free-standing graphene sheets are now held together by the carbon phase, acting as a bridge for uninterrupted movement of electrons and phonons.

3) the specific conductivity value of the hybrid foam material of the present invention represents a value of 250 to 500 W/mK per unit specific gravity; Specific conductivity values of other types of foam materials are typically less than 250 W/mK per unit specific gravity.

4) Thermal conductivity data for a series of 3D graphene-carbon foams and a series of pure graphene derived foams are summarized in Figure 5, both plotted against final (maximum) heat treatment temperature. For both types of materials, the thermal conductivity increases monotonically with final HTT. However, the method of the present invention enables the production of graphene-carbon foam that surpasses pure graphene foam in a cost-effective and environmentally friendly manner. This is another unexpected result.

5) Figure 4b shows the thermal conductivity values of the hybrid foam and hydrothermally reduced GO graphene foam of the present invention. The electrical conductivity values of 3D graphene-carbon foam and hydrothermally reduced GO graphene foam are shown in Figure 6. This data further supports the notion that, given equal amounts of solid material, the graphene-carbon foams of the present invention are inherently the most conductive, reflecting the importance of continuity in electron and phonon transport paths. The carbon phase bridges gaps or interruptions between graphene sheets.

Example 10 : Properties 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 peaks at about 2θ = 26°, which corresponds to an intergraphene spacing (d ₀₀₂ ) of about 0.3345 nm. The graphene walls of the hybrid foam material typically exhibit an inter-graphene spacing (d ₀₀₂ ) of 0.3345 nm to 0.40 nm, but more typically up to 0.34 nm.

When the foam structure is compressed at a heat treatment temperature of 2,750°C for 1 hour, the d ₀₀₂ spacing decreases to about 0.3354 nm, which is the same as the d ₀₀₂ spacing of a graphite single crystal. Additionally, a second diffraction peak appears with high intensity at 2θ = 55°, corresponding to X-ray diffraction from the (004) plane. The (004) peak intensity relative to the (002) intensity in the same diffraction curve, or the I (004)/ I (002) ratio, is a good indicator of the degree of crystal integrity and preferential orientation of the graphene planes. For all graphite materials heat-treated at temperatures lower than 2,800°C, the I (004)/ I (002) ratio is less than 0.1, and the (004) peak is absent or relatively weak. The I (004)/ I (002) ratio for graphitic materials heat treated at 3,000-3,250° C. (e.g., highly oriented pyrolytic graphite, HOPG) ranges from 0.2 to 0.5. In contrast, graphene foams prepared with a final HTT of 2,750 °C for 1 h exhibit an I (004)/ I (002) ratio of 0.78 and a mosaic dispersion value of 0.21, indicating that the pore walls have a good degree of preferential orientation. It indicates a substantially complete graphene single crystal (when manufactured under compressive force).

The “mosaic dispersion” value is obtained from the full width at half maximum of the (002) reflection in the X-ray diffraction intensity curve. This indicator of ordering characterizes the graphite or graphene crystal size (or grain size), amount of grain boundaries and other defects, and preferred crystal orientation. A nearly perfect single crystal of graphite is characterized by a mosaic dispersion value of 0.2 to 0.4. Some of the graphene foams of the present invention have a mosaic dispersion value in the range of 0.3 to 0.6 when manufactured using a final heat treatment temperature of 2,500°C or higher.

Here is a summary of some of the more important results:

1) In general, adding impact balls helps accelerate the process of exfoliation of graphene sheets from graphite particles. However, this option requires separation of the impact balls after manufacturing the graphene-coated polymer particles.

2) If impact balls (e.g. ceramic, glass, metal balls, etc.) are not used, harder polymer particles (e.g. PE, PP, nylon, ABS, polystyrene, high impact polystyrene, etc. and their fillers) reinforcement forms) can better exfoliate graphene sheets from graphite particles compared to softer polymer particles (e.g., rubber, PVC, polyvinyl alcohol, latex particles).

3) Without adding impact balls externally, given the same 1 hour run time, the softer polymer particles are graphene-rich with 0.001 wt% to 5 wt% graphene (mainly single-layer graphene sheets). Tend to produce coating or embedded particles, harder polymer balls tend to produce graphene-coated particles with 0.01% to 30% by weight graphene (mainly single-layer and few-layer graphene sheets). .

4) When impact balls are added externally, all polymer balls will support from 0.001% to about 80% by weight graphene sheets (for graphene sheets greater than 30% by weight, mainly few-layer graphene, less than 10 layers). You can.

5) The graphene-carbon hybrid foam materials of the present invention typically have significantly higher structural integrity (e.g., compressive strength, elasticity, and resilience) and higher thermal stability compared to counterparts prepared by conventional prior art methods. Indicates conductivity and electrical conductivity.

6) All prior art processes for making graphite foam or graphene foam appear to provide only macroporous foams with physical densities in the range of about 0.2 to 0.6 g/cm3 and pore sizes that are sufficient for most intended uses. It is usually too large (eg 20 to 300 μm). In contrast, the present invention provides a method of producing graphene foam that can have densities as low as 0.001 g/cm3 and as high as 1.7 g/cm3. Pore sizes can vary from microscopic (less than 2 nm) to mesoscopic (2-50 nm) to macroscopic (e.g., 1-500 μm). This level of flexibility and versatility in designing different types of graphene-carbon foams is unprecedented and unmatched by any prior art method.

7) The method of the present invention also responds to various application needs (e.g., recovery of oil from oil-contaminated water, separation of organic solvents from water or other solvents, heat dissipation, etc.) by adjusting the chemical composition (e.g., F , O and N contents, etc.) enables convenient and flexible control.

In conclusion, we have successfully developed a completely new, novel, unexpected, and distinctly different type of highly conductive graphene-carbon hybrid foam material, device, and associated manufacturing process. The chemical composition (% of oxygen, fluorine, and other non-carbon elements), structure (crystal integrity, grain size, number of defects, etc.), crystal orientation, morphology, manufacturing method, and properties of this new class of foam materials are known as mesophase pitch. It is fundamentally different and clearly distinct from induced graphite foam, CVD graphene derived foam, and graphene foam from hydrothermal reduction of GO.

Claims (41)

An integrated 3D graphene-carbon hybrid foam consisting of multiple pores and pore walls, wherein the pore walls are made of carbon material with a carbon material-to-graphene weight ratio of 1/200 to 1/2. It includes a single-layer or few-layer graphene sheet chemically bonded by, wherein the few-layer graphene sheet has an interplanar spacing d ₀₀₂ of 0.3354 nm to 0.40 nm as measured by X-ray diffraction. Overlapping graphene planes 2 to 10 layers, wherein the single-layer or few-layer graphene sheet is a pristine graphene material containing essentially 0% non-carbon elements, or 0.001% to 25% by weight of non-carbon elements. It includes a non-pristine graphene material having, wherein the non-pure graphene includes graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, An integral 3D graphene-carbon hybrid foam selected from hydrogenated graphene, graphene nitride, doped graphene, chemically functionalized graphene, or combinations thereof. The method of claim 1, wherein the 3D graphene-carbon hybrid foam has a density of 0.005 to 1.7 g/cm3, a specific surface area of 50 to 3,200 m2/g, a thermal conductivity of at least 200 W/mK per unit specific gravity, and/or An integrated 3D graphene-carbon hybrid foam with an electrical conductivity of more than 2,000 S/cm per specific gravity. 2. The integral 3D foam of claim 1, wherein the pore walls comprise pure graphene and the 3D graphene-carbon hybrid foam has a density of 0.01 to 1.7 g/cm3, or an average pore size of 2 nm to 50 nm. Graphene-carbon hybrid foam. 2. The method of claim 1, wherein the pore walls comprise impure graphene material, and the foam comprises a non-carbon element content ranging from 0.01% to 20% by weight, wherein the non-carbon elements include oxygen, fluorine, and chlorine. , an integral 3D graphene-carbon hybrid foam comprising an element selected from bromine, iodine, nitrogen, hydrogen, or boron. The integral 3D graphene-carbon hybrid foam of claim 1, wherein the pore walls include graphene fluoride, and the graphene-carbon hybrid foam includes a fluorine content of 0.01% to 15% by weight. The integral 3D graphene-carbon hybrid foam of claim 1, wherein the pore walls comprise graphene oxide, and the graphene-carbon hybrid foam comprises an oxygen content of 0.01% to 20% by weight. The integrated 3D graphene-carbon hybrid foam of claim 1, wherein the foam has a specific surface area of 200 to 3,000 m2/g, or a density of 0.1 to 1.2 g/cm3. 2. The monolithic 3D graphene-carbon hybrid foam according to claim 1, in the form of a continuous length 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. 2. The method of claim 1, wherein the foam has an oxygen content or non-carbon content of less than 1% by weight, and the pore walls have an intergraphene spacing of less than 0.35 nm, a thermal conductivity of at least 250 W/mK per unit of gravity, and/or An integrated 3D graphene-carbon hybrid foam with an electrical conductivity of more than 2,500 S/cm per unit specific gravity. 2. The method of claim 1, wherein the foam has an oxygen content or a non-carbon content of less than 0.01% by weight, and the pore walls have an inter-graphene spacing of less than 0.34 nm, a thermal conductivity of at least 300 W/mK per unit of gravity, and/or An integrated 3D graphene-carbon hybrid foam comprising overlapping graphene planes with an electrical conductivity of more than 3,000 S/cm per unit specific gravity. 2. The method of claim 1, wherein the foam has an oxygen content or a non-carbon content of less than 0.01% by weight, and the pore walls have an inter-graphene spacing of less than 0.336 nm, a thermal conductivity of at least 350 W/mK per unit of gravity, and/or An integrated 3D graphene-carbon hybrid foam comprising overlapping graphene planes with an electrical conductivity of more than 3,500 S/cm per unit specific gravity. 2. The method of claim 1, wherein the foam comprises overlapped graphene planes having an inter-graphene spacing of less than 0.336 nm, a thermal conductivity of greater than 400 W/mK per unit of gravity, and/or an electrical conductivity of greater than 4,000 S/cm per unit of gravity. A monolithic 3D graphene-carbon hybrid foam having a pore wall comprising. The integral 3D graphene-carbon hybrid foam of claim 1, wherein the pore walls comprise overlapping graphene planes with an inter-graphene spacing of less than 0.337 nm and a mosaic dispersion value of less than 1.0. 2. The monolithic 3D graphene-carbon hybrid foam of claim 1, wherein the pore walls comprise a 3D network of interconnected graphene planes. The integral 3D graphene-carbon hybrid foam of claim 1, wherein the foam includes meso-scaled pores with a pore size of 2 nm to 50 nm. An oil-removal or oil-separation device comprising the 3D graphene-carbon hybrid foam of claim 1 as an oil-absorbing element. A solvent-removal or solvent-separation device comprising the 3D graphene-carbon hybrid foam of claim 1 as a solvent-absorbing or solvent-separating element. As a method for separating oil from water,
a. Providing an oil-absorbing element comprising the integral 3D graphene-carbon hybrid foam of claim 1;
b. contacting the oil-water mixture with the element to absorb oil from the mixture;
c. withdrawing the urea from the mixture and extracting oil from the urea; and
d. Steps to reuse the above elements
How to include . A method for separating an organic solvent from a solvent-water mixture or a multi-solvent mixture, comprising:
a. Providing an organic solvent-absorbing or solvent-separating element comprising the integral 3D graphene-carbon hybrid foam of claim 1;
b. contacting the element with an organic solvent-water mixture or multi-solvent mixture comprising a first solvent and at least a second solvent;
c. allowing said element to absorb organic solvent from the mixture or to separate said first solvent from said at least second solvent; and
d. withdrawing the urea from the mixture and extracting an organic solvent or a first solvent from the urea; and
e. Steps to reuse the above elements
How to include . A thermal management device comprising the 3D integrated graphene-carbon hybrid foam of claim 1 as a heat diffusion or heat dissipation element. 21. The method of claim 20, wherein a heat exchanger, a heat sink, a heat pipe, a highly conductive insert, a conductive plate between the heat sink and the heat source, a heat-diffusing component, a heat dissipation component, a thermal interface medium, or a thermoelectric A thermal management device comprising a device selected from a cooling device or a Peltier cooling device. A method for producing an integrated 3D graphene-carbon hybrid foam directly from graphitic material, comprising:
(a) mixing multiple particles of a graphitic material and multiple particles of a solid polymeric carrier material to form a mixture in an impacting chamber of an energy impacting apparatus;
(b) operating the energy impact device for a long period of time at a frequency and intensity sufficient to exfoliate the graphene sheet from the graphitic material and move the graphene sheet to the surface of the solid polymer carrier material particle to form a graphene-coating or producing graphene-embedded polymer particles in the impact chamber;
(c) recovering the graphene-coated or graphene-inserted polymer particles from the impact chamber and incorporating the graphene-coated or graphene-inserted polymer particles into a graphene-polymer composite structure of a desired shape; and
(d) thermally decomposing the graphene-polymer composite structure of the above type and thermally converting the polymer into carbon or graphite that binds the pores and the graphene sheet to form the integrated 3D graphene-carbon hybrid foam.
method, including 23. The method of claim 22, wherein a plurality of impact balls or mediators are added to the impact chamber of the energy impact device. 24. The method of claim 23, wherein step (c) comprises actuating a magnet to separate the impact ball or mediator from the graphene-coated or graphene-embedded polymer particles. 23. The method of claim 22, wherein the particles of solid polymer material are 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 between 100 nm and 1 mm. 23. The method of claim 22, wherein the solid polymer is selected from solid particles of thermoplastics, thermosets, rubbers, semi-penetrating network polymers, penetrating network polymers, natural polymers, or combinations thereof. 23. The method of claim 22, wherein the solid polymer is partially removed prior to step (d) by melting, etching, or dissolving in a solvent. The method of claim 22, wherein the graphite material is natural graphite, synthetic graphite, highly oriented pyrolytic graphite, graphite fiber, graphite nanofiber, graphite fluoride, graphite oxide, chemically modified graphite, exfoliated graphite, ash. A method selected from compressed exfoliated graphite, expanded graphite, meso carbon microbeads, or combinations thereof. 23. The method of claim 22, wherein the energy impact device is a vibrating 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 tumbler ball mill, a continuous ball mill, etc. Ball mill, stirred ball mill, pressurized ball mill, freezer mill, vibrating sieve, bead mill, nano bead mill, ultrasonic homogenizer mill, centrifugal planetary mixer, vacuum ball mill, or resonant acoustic mixer ( resonant acoustic mixer) method. 23. The method of claim 22, wherein the graphitic material comprises non-intercalated and non-oxidized graphitic material that has not been exposed to a chemical or oxidizing treatment prior to the mixing step. The method of claim 22, wherein the solid polymer is phenolic resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, poly A carbon yield selected from benzothiazole, polybenzobithiazole, poly(p-phenylene vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof. A method comprising high polymer content. 23. The method of claim 22, wherein the solid polymer is polyethylene, polypropylene, polybutylene, polyvinyl chloride, polycarbonate, acrylonitrile-butadiene (ABS), polyester, polyvinyl alcohol, polyvinylidene fluoride (PVDF). , polytetrafluoroethylene (PTFE), polyphenylene oxide (PPO), polymethyl methacrylate (PMMA), copolymers thereof, polymer blends thereof, or combinations thereof. Including, method. The method of claim 22, wherein the thermal decomposition step is performed by carbonizing the polymer at a temperature of 200°C to 2,500°C to obtain a graphene-carbon foam, or carbonizing the polymer at a temperature of 200°C to 2,500°C to obtain a graphene-carbon foam. After obtaining, the graphene-carbon foam is graphitized at 2,500°C to 3,200°C to obtain a graphitized graphene-carbon foam. 23. The method of claim 22, wherein the integrating step melts the polymer particles to form a polymer melt mixture with graphene sheets dispersed therein, and molds the polymer melt mixture into a desired shape to form a graphene-polymer composite structure. A method comprising coagulating with. 23. The method of claim 22, wherein the integrating step is performed by dissolving the polymer particles in a solvent to form a polymer solution mixture with graphene sheets dispersed therein, molding the polymer solution mixture into a desired shape, and removing the solvent. A method comprising solidifying the form into the graphene-polymer composite structure. 23. The method of claim 22, wherein the incorporating step includes forming the graphene-coated polymer particles into a composite shape selected from rods, sheets, films, fibers, powders, ingots, or block shapes. 23. The method of claim 22, wherein the consolidating step is performed after compressing the graphene-coated polymer particles into a porous molded body having macroscopic pores, and then selecting from petroleum pitch, coal tar pitch, aromatic organic materials, monomers, organic polymers, or combinations thereof. A method comprising infiltrating or impregnating the pores with an additional carbon source material. The method of claim 38, wherein the organic polymer is phenolic resin, polyfurfuryl alcohol, polyacrylonitrile, polyimide, polyamide, polyoxadiazole, polybenzoxazole, polybenzobisoxazole, polythiazole, poly A carbon yield selected from benzothiazole, polybenzobithiazole, poly(p-phenylene vinylene), polybenzimidazole, polybenzobisimidazole, copolymers thereof, polymer blends thereof, or combinations thereof. Methods containing high polymer 23. The method of claim 22, wherein said consolidating step includes forming a quantity of said graphene-coated or graphene-embedded polymer particles into a compact. 41. The method of claim 40, wherein the compact is in a form selected from rods, sheets, films, fibers, powders, ingots, or blocks.