WATER, BUBBLE COLLAPSE AND SYNGAS SPECIES IN THE SYNTHESIS OF GRAPHENE AND ITS DERIVATIVES

Abstract

Hydrodynamic cavitation-inducing inertial, non-inertial, and combination reactors are employed in the hydrothermal synthesis of graphene and its derivatives, both in solution and vapor. Various hydrodynamic cavitation reactor embodiments are revealed. Water is used to both nucleate and self-heal graphene sheet growth in solution and vapor. Various methods of combustion, hydrothermal and dehydration synthesis of graphene and its derivatives are revealed. Additionally, water and ice are used as a substrate, both alone and in combination with other substrates, to grow and recover useful graphene and its derivatives.

Claims

1. A method of graphene synthesis, comprising: (a) creation of synthesis gas species from the hydrothermal heating of a carbonaceous material in a reaction chamber; (b) collection, direction and removal of the resulting vapors from the reaction chamber to a substrate; and (c) deposition of graphene on the surface of the substrate.

2. The method of claim 1, wherein the substrate comprises water.

3. The method of claim 2, further comprising application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the substrate.

4. The method of claim 1, wherein the substrate comprises ice or dry ice.

5. The method of claim 1, wherein the substrate comprises a solid surface, wherein the solid surface is coated at least in part with liquid water (H.sub.2O), deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2) or combinations thereof.

6. The method of claim 5, wherein the solid surface comprises silicon, copper, nickel, cobalt, boron, iron, gold, silver, aluminum, germanium, boron nitride, glass, ceramic, biomimetic membrane, silicon dioxide, silica, aluminum silicate, fused silica, silicon carbide, plastics, polymers, resins, epoxy, titanium, concrete, steel, asphalt, cement, nylon, graphite, diamond, amorphous carbon, h-BN, Si.sub.3N.sub.4, poly(2-phenylpropyl)methysiloxane (PPMS), poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(acrylonitrile-co-butadiene-co-styrene) (AB).

7. The method of claim 1, wherein the substrate comprises a solid surface, wherein the solid surface is coated at least in part with ice.

8. The method of claim 1, wherein the hydrothermal heating comprises heating the reaction chamber by application of a flame, an electric heating element, an electrical arc discharge or combinations thereof.

9. The method of claim 8, wherein the reaction chamber comprises a non-inertial cavitation-inducing reactor.

10. The method of claim 9, wherein the non-inertial cavitation-inducing reactor comprises an external energy input comprising ultrasound waves, acoustic levitation waves, pulsed laser light, radio frequency (RF) emissions, electromagnetic emissions, MASER, SASER or combinations thereof.

11. The method of claim 9, wherein the reactor chamber comprises an inertial cavitation-inducing reactor.

12. The method of claim 11, wherein the inertial cavitation-inducing reactor comprises a flow restricting venturi-type element, wherein the flow restricting venturi-type element comprises a curved venturi channel designed to induce cyclonic flow.

13. The method of claim 1, wherein heating the carbonaceous material comprises pyrolysis.

14. The method of claim 1, wherein heating the carbonaceous material comprises an oxidation/reduction chemical reaction.

15. The method of claim 14, wherein the oxidation/reduction chemical reaction comprises dehydration of the carbonaceous material.

16. The method of claim 15, wherein the dehydrated carbonaceous material comprises sugar.

17. The method of claim 1, wherein the reaction chamber comprises an autoclave.

18. The method of claim 1, wherein the synthesis gas species comprise under carbon monoxide, nascent hydrogen ions, ionic methane precursor gases and combinations thereof.

19. A method of graphene oxide synthesis, comprising: (a) creation of synthesis gas species in the presence of an oxidizing agent from the hydrothermal heating of a carbonaceous material in a reaction chamber; (b) collection, direction and removal of the resulting vapors from the reaction chamber to a substrate; and (c) deposition of graphene oxide on the surface of the substrate.

20. The method of claim 19, further comprising application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the substrate.

21. A method of graphene synthesis, comprising: (a) creation of synthesis gas species from the hydrothermal heating of a carbonaceous material in a reaction chamber; and (b) collection, direction and removal of the resulting vapors from the reaction chamber to a substrate.

22. The method of claim 21, wherein the substrate comprises water, wherein the method further comprises application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the substrate.

23. A method of graphene oxide synthesis, comprising: (a) creation of synthesis gas species in the presence of an oxidizing agent from the hydrothermal heating of a carbonaceous material in a reaction chamber; and (b) collection, direction and removal of the resulting vapors from the reaction chamber to a substrate.

24. The method of claim 23, wherein the substrate comprises water, wherein the method further comprises application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the substrate.

25. A method of graphene synthesis, comprising: (a) application of a carbonaceous vapor containing C.sub.1 to C.sub.5 radicals to an aqueous solution; and (b) recovery of graphene from the surface of the aqueous solution.

26. The method of claim 25, further comprising application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the aqueous solution.

27. A method of graphene oxide synthesis, comprising: (a) application of a carbonaceous vapor containing C.sub.1 to C.sub.5 radicals to an aqueous solution; and (b) recovery of graphene oxide from surface of the aqueous solution.

28. The method of claim 27, further comprising application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the aqueous solution.

29. A method of graphene hydrogel synthesis, comprising: (a) application of a carbonaceous vapor containing C.sub.1 to C.sub.5 radicals to an aqueous solution; and (b) recovery of a graphene hydrogel layer from the aqueous solution.

30. The method of claim 29, further comprising application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the aqueous solution.

31. A method of graphene oxide hydrogel synthesis, comprising: (a) application of a carbonaceous vapor containing C.sub.1 to C.sub.5 radicals to an aqueous solution; and (b) recovery of a graphene oxide hydrogel layer from the aqueous solution.

32. The method of claim 31, further comprising application of sonication, ultrasonication, surfactant, oxidizing agents, reducing agents, ionizing irradiation, pH adjustment, pressurization, depressurization, heating, vibration, UV radiation, DUV radiation, sound waves, microwaves, magnetism, MASER (Microwave Amplification by Simulated Emission of Radiation), SASER (Sound Amplification by Simulated Emission of Radiation), electric current, electrical arc, heat, cooling, deuterium oxide (D.sub.2O), semi-heavy water (HDO), hydrogen peroxide (H.sub.2O.sub.2), glycol or combinations thereof to the aqueous solution.

33. A method of composite fabrication, comprising: (a) application of a graphene hydrogel produced according to the method of claim 29, to a liquid composite mixture prior to its curing into a solid; and (b) curing the composite mixture into a solid.

34. A method of composite fabrication, comprising: (a) application of a graphene oxide hydrogel produced according to the method of claim 31, to a liquid composite mixture prior to its curing into a solid; and (b) curing the composite mixture into a solid.

35. A method of graphene synthesis, comprising: (a) application of a cyclic-carbon containing aqueous solution to coat a substrate that is sufficient to withstand the heat of pyrolysis of the aqueous solution; (b) pyrolysis of the aqueous solution coating on the substrate under conditions to produce graphene; and (c) recovery of graphene from the surface of the substrate.

36. A method of surface graphitized abrasive nanoparticle synthesis, comprising: (a) ball milling of a carbonaceous material in the presence of a solvent to create a slurry; (b) addition of a metal oxide powder or a nano-powder to the slurry; and (c) recovery of surface graphitized abrasive nanoparticles from the slurry.

37. The method of claim 36, wherein the carbonaceous material comprises solid CO.sub.2 (dry ice), bituminous coal, peat, lignite, sub-bituminous coal, pulverized coal, nano-coal, steam coal, cannel coal, anthracite, charcoal, carbon black, activated charcoal, activated nano-coal, sugar char and combinations thereof.

38. The method of claim 36, wherein the solvent comprises cyclohexane, toluene, polyphenol, benzaldehyde, benzotriazole, benzyl 1-naphthyl carbonate, benzene, ethyl benzene, styrene, benzonitrile, phenol, phthalic anhydride, phthalic acid, terephthalic acid, p-toluic acid, benzoic acid, aminobenzoic acid, benzyl chloride, isoindole, ethyl phthalyl ethyl glycolate, N-phenyl benzamine, methoxybenzoquinone, benzylacetone, benzylideneacetone, hexyl cinnamaldehyde, 4-amino-2-hydroxytoluene, 3-aminophenol, a benzoate, terpene, ethanol, methanol, isopropanol, isobutane, cyclobutane, pentane, isopentane, neopentane, cyclopentane, hexane, octane, kerosene, an ester, a ketone, an aldehyde, an ether or combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 is a schematic and image of a common vacuum eductor (jet spray nozzle) apparatus.

[0041] FIG. 2 is a schematic image of a reversed-flow eductor, inertial cavitation-inducing apparatus.

[0042] FIG. 3 is a picture of a commercially available inertial cavitation water heater apparatus.

[0043] FIG. 4A is the inlet of a cyclonic flow inducing restrictive venturi inertial cavitation-inducing device.

[0044] FIG. 4B is the outlet of a cyclonic flow inducing restrictive venturi inertial cavitation-inducing device.

[0045] FIG. 4C is a longitudinal view of a cyclonic flow inducing restrictive venturi inertial cavitation-inducing device.

[0046] FIG. 5A is an embodiment of an offset flow inertial cavitation-inducing reactor embodiment.

[0047] FIG. 5B is the longitudinal view of the embodiment depicted in FIG. 5A.

[0048] FIG. 5C is another embodiment of an offset flow inertial cavitation-inducing reactor.

[0049] FIG. 6 is an opposing right-angle flow inertial cavitation-inducing reactor embodiment.

[0050] FIG. 7 is an ultrasonic transducer rod, capable of addition to a cavitation reactor.

[0051] FIG. 8 is a picture of a commercially available dual shut-off valve.

[0052] FIG. 9A is a schematic of a combination ultrasonic/inertial cavitation-inducing reactor.

[0053] FIG. 9B is a detailed view of the incorporated ultrasonic transducer horn within FIG. 9A.

[0054] FIG. 10 is an embodiment of a hydrodynamic cavitation reactor.

[0055] FIG. 11 is a structural diagram of methyl radical.

[0056] FIG. 12 is a representation of a single carbon atom in a guest/host relationship with a water cage.

[0057] FIG. 13 is a representation of 6 carbon/water clathrate cages aligned in a helix.

DETAILED DESCRIPTION OF THE INVENTION

[0058] It is theorized in the science of the invention that carbon radicals and nascent hydrogen ions play an important role in the disclosed synthesis methods, regardless of the means employed to generate those carbon radicals or hydrogen ions from their carbonaceous precursors. Likewise, it is theorized that water plays an equally important role in the formation of graphene from such carbon radicals. The invention relates to methods of graphene and graphene derivatives synthesis by various techniques and through various reactor designs, with subsequent purposeful collection and direction of the resulting vapors to a liquid or solid substrate whereby graphene or its derivatives are permanently deposited or recovered for other use.

[0059] Hydrothermal Synthesis of Graphene and its Derivatives

[0060] Hydrothermal synthesis routes to graphene and its derivatives are disclosed, in which polycyclic aromatic hydrocarbon (PAH) graphene sheet precursors and formed graphene scales in aqueous vapors can be purposefully collected and separated from the liquid-phase reactants in which they were formed. Additionally, the hydrothermal (wet) routes to graphene synthesis of the invention are not believed to incur the irretrievable folding/crumpling of graphene sheets, small graphene sheet size, and imperfections in the graphene hexagonal lattice structure that are commonly experienced in dry synthesis methods.

[0061] In the methods disclosed herein, a myriad of possible carbonaceous feedstock reactants can be utilized to produce graphene and graphitic materials without requiring the use of toxic, explosive, caustic, complex or expensive materials. The hydrothermal routes to graphene synthesis of the invention are believed to provide a safe, industrially-scalable, and cost effective method for synthesis of graphene and its derivatives, thereby permitting widespread global commercialization of new graphene-based technologies.

[0062] In one embodiment, methane, ethane, propane or combinations thereof can be bubbled in conjunction with hydrogen gas (H2), through alcohol solvents in a heated hydrothermal reactor chamber (see Wassei, et al., Chemical Vapor Deposition of Graphene on Copper from Methane, Ethane and Propane: Evidence of Bilayer Selectivity, Small, Vol. 8, Issue 9, 2012, pp. 1415-1422). The resulting vapors can then be collected and channeled, according to methods of the invention, through aqueous solutions for hydrophobic self-assembly of graphene sheets. Alternatively, the resulting vapors can be collected and directed to the surface of a solid substrate for the formation of graphene and its derivatives.

[0063] Combustion Synthesis of Graphene and its Derivatives

[0064] In one embodiment, polytetraflouroethylene (PTFE) can be heated in a mild vacuum to its thermal decomposition into certain fluorocarbon gases (i.e. tetrafluoroethylene, C2F4) and while being simultaneously reacted with silicon carbide powder in a self-sustaining exothermic reaction to produce carbon-rich vapors (see Manukyan et al., Combustion synthesis of graphene materials, Carbon, Vol. 62, October 2013, pp. 302-311). The resulting vapors can then collected and channeled, according to methods of the invention, through aqueous solutions for hydrophobic self-assembly of graphene sheets.

[0065] In another embodiment, methane gas can be combusted along with pure oxygen (O2) gas in a chamber designed to induce so-called convective eddies (reflux vortexes) that encourage the development of hot and cold zones (see Kellie et al., Deposition of few-layered graphene in a microcombuster on copper and nickel substrates, RSC Adv., Vol. 3, 2013, pp. 7100-7105). It is noteworthy that the oxidation of methane itself (through a methanol intermediate) produces water. The resulting exhaust vapors can then be collected and channeled, according to methods of the invention, through liquid water solutions for hydrophobic self-assembly of graphene sheets. Alternatively, the resulting vapors may be collected and directed to the surface of a solid substrate for the formation of graphene and its derivatives.

[0066] Dehydration and Rapid Oxidation/Reduction Synthesis of Graphene

[0067] In one embodiment, sugar, sodium bicarbonate and ignited alcohol or lighter fluid accelerant can be used to create a graphene/PAH-rich exhaust vapor. Other embodiments can employ ignited mixtures of nitrated linseed oil and naphthalenes. Still other embodiments can use an ignited combination of ammonium nitrate and sodium bicarbonate mixed with water/ammonium dichromate. In yet another embodiment, the aforementioned ammonium dichromate can be substituted with a flammable accelerant. The resulting exhaust vapors can then be, according to methods of the invention, collected and channeled through aqueous solutions for hydrophobic self-assembly of graphene sheets. Alternatively, the resulting vapors can then be collected and directed to the surface of a solid substrate for the formation of graphene and its derivatives.

[0068] In other illustrative embodiments, so-called oxidative pyrolysis of methane or other carbonaceous gases can be employed to produce the necessary graphene/PAH-rich exhaust vapors for graphene or graphene derivatives synthesis.

[0069] Hydrodynamic Cavitation Reactors for Wet Graphene Synthesis

[0070] Various embodiments of hydrothermal cavitation reactors are disclosed that encourage the formation of cavitation bubbles and their subsequent complete collapse, releasing the useful energy potential of supercritical water. In each embodiment, the vapors created can then be collected and channeled through liquid water solutions, according to methods of the invention, for hydrophobic self-assembly of graphene sheets. Alternatively, the resulting vapors can be collected and directed to the surface of a solid substrate for the formation of graphene and its derivatives.

[0071] In one embodiment, the flow directions of a common vacuum eductor apparatus (as seen in FIG. 1) can be reversed, such that the vacuum inlet is converted to a horizontal product flow discharge, and the jet spray outlet in likewise reversed into a venturi-type nozzle inlet; thus causing accelerated stream collision and cavitation bubble formation within the eductor apparatus' (former) mixing and air-entrainment chamber (as seen in FIG. 2). In this embodiment's design, the liquid streams are purposefully intended to accelerate prior to collision with each other, in a chamber or cavity providing a low-pressure area designed or employed to induce inertial cavitation bubble formation within the combined (mixed) reactant streams and resulting local bubble harvesting (BH) to capture the formed bubbles and maintain them (albeit temporarily) in the area of nanopartical nucleation and growth. During resulting BH and cavitation bubble collapse, these bubbles provide a nano-environment suitable for inducing nanoparticle synthesis, such as nucleating graphene (and its derivatives) formation and growth.

[0072] In another embodiment, a commercially-available rotating drum-type inertial cavitation-inducing (water heater) reactor (as seen in FIG. 3) can be employed to heat the fluids of a hydrothermal graphene synthesis system to create heated, superheated and/or supercritically heated water. In another embodiment, the pits or cavities along the surface of a rotating internal drum provide the sites for cavitation bubble formation and local BH. The resulting heated water can then be employed within the reactor chamber to nucleate graphene particle synthesis and encourage its continued growth by providing the necessary ions and radicals to accomplish graphene synthesis from carbonaceous materials heated to their point of decomposition in aqueous solution.

[0073] In another embodiment, a flow-restricting venturi device (FIG. 4C) can be employed to induce a (longitudinal vortex) cyclonic liquid flow, further comprising a vacuum sheath (VS) or tornadic so-called supercavitation event in the fluid stream; this vacuum-sheathed liquid cyclone conveniently occurring in the direction of flow of the system. In this embodiment, the entrance (inflow) orifice (FIG. 4A) is smaller than the exit (outflow) orifice (FIG. 4B), so as to create a lower pressure area at the exit as compared to the entrance. The aforementioned cyclonic flow may also be achieved by the offset opposing flow design embodiments (FIGS. 5A, 5B, 5C), designed to purposefully collide opposing flows at an angle to each other, rather than head on, so as to induce a circular flow about the collision within an inertial cavitation reactor chamber.

[0074] In another embodiment, an opposing right-angle flow inertial cavitation-inducing reactor (FIG. 6) can be employed to initiate cavitation bubbles at a right-angle juncture in the inlet flow, just prior to opposing collision of the two reactant streams. This opposing right-angle flow cavitation can be accomplished by reversal of the flow directions through a typical commercially available dual shut-off valve apparatus (as seen in FIG. 8).

[0075] In another embodiment, external non-inertial means can be employed to induce cavitation bubble formation within a reactor chamber. The means for producing such external energy for inducing cavitation in the fluid inside the reactor may comprise ultrasonic soundwave energy, delivered into the chamber by means of a transducer rod (as seen in FIG. 7) inserted or machined into the chamber.

[0076] In another embodiment, means for producing external energy for inducing non-inertial cavitation in the fluid inside the reactor may comprise radio frequency (RF) non-ionizing irradiation. In one design embodiment, the RF energy can be transmitted directly between two plates (transmitter and receiver) so as to maximize the signal delivered to the reactants in the chamber situated between them (see, for example, U.S. Patent Application No. 2009/0294300 by Kanzius, J.). The resulting heated water can then be employed within the reactor chamber to nucleate graphene particle synthesis and encourage its continued growth by providing the necessary ions and radicals to accomplish graphene synthesis from carbonaceous materials heated to their point of decomposition in aqueous solution.

[0077] In another embodiment, means for producing external energy for inducing non-inertial cavitation in the fluid inside the reactor may comprise strongly-focused laser light emissions (see Vogel et al., Optical and acoustic investigations of the dynamics of laser-produced cavitation bubbles near a solid boundary, J. Fluid Mech., Vol. 206, 1989, pp. 299-338). The ability of laser light emissions to induce cavitation bubble formation in liquids is known to the art (see, for example, Yan et al., Hollow nanoparticle generation on laser-induced cavitation bubbles via bubble interface pinning, Appl. Phys. Lett., Vol 97, Issue 12, 2010; Yan, Z. and Chrisey, D. B., Pulsed laser ablation in liquid for micro-/nanostructure generation, J. of Photochemistry and Photobiology, Vol. 13, Issue 3, September 2012, pp. 204-223; Vogel, A. et al., Energy density, temperature and pressure upon spherical cavitation bubble collapse compared to femtosecond and nanosecond optical breakdown, Lasers and Elecro-Optics 2009/European Quantum Electronics Conference (CLEO-Europe, EQEC 2009) [IEEE Conference Publication], Jun. 14-19, 2009, Munich, Germany) Manipulation of bubble size and physical position is likewise possible with the use of spacial light modulator (SLM) technologies (see, for example, Quinto-su et al., Generation of laser-induced cavitation bubbles with a digital hologram, Optics Express, Vol. 16 (23), 2008, pp. 18964-18969). In another embodiment, the light wavelength can be in the UV spectrum to, among other things, encourage the photolytic dissociation of water into mono-atomic hydrogen ions (see, for example, Getoff, N. and Schneck, G. O., Primary Products of Liquid Water Photolysis at 1236, 1470 and 1849 , Photochem. and Photobio., Vol. 8, Issue 3, September 1968, pp. 167-178). In another embodiment, the supplied RF energy can be in the form of two or more frequencies combined (e.g. heterodyning) to stretch or break the intermolecular bonds of water, the carbonaceous feedstock materials or intermediates thereof, to produce useful radicals (see generally, the work of Puharich, A., MD (1918-1995, Dobson, N.C., U.S.), on water decomposition to produce nascent hydrogen; U.S. Pat. No. 4,394,230 to Puharich; and the work of Meyer, S (Grove City, Ohio, US), on resonant electrolysis of water molecules). The resulting heated water can then be employed within the reactor chamber to nucleate graphene particle synthesis and encourage its continued growth by providing the necessary ions and radicals to accomplish graphene synthesis from carbonaceous materials heated to their point of decomposition in aqueous solution. It is further theorized that the LPSC of the collapsing cavitation bubbles in the reactors of the present invention may provide the necessary physical conditions, when coupled with the introduction of electron irradiation (or other ionizing irradiation), UV, or specifically DUV irradiation, to produce enhanced photolytic/radiolytic dissociation of water into hydrogen ions (see, for example, Ceppatelli, M., High-pressure photodissociation of water as a tool for hydrogen synthesis and fundamental chemistry, Pro. Nat. Acad. Sci., Vol. 106, No. 28, Jul. 14, 2009, pp. 11454-11459). It is further theorized, in the science of the invention, that hydrogen (as synthesized and employed in various embodiments of the invention) selectively attacks the CH bonds of the carbonaceous material feedstocks and encourages the formation of carbon radicals and the subsequent assembly of CC bonds necessary to form graphene and its derivatives (see Tribecky, T., Hyperthermal H2 induced CH bond cleavage: A Novel Approach To Cross-linking Of Organic Molecules, 2011, University of Western OntarioElectronic Thesis and Dissertation Repository, Paper No. 270; later published as Trebicky, T., Cleaving CH bonds with hydrothermal H2: facile chemistry to cross-link organic molecules under low-chemical- and energy-loads, Green Chem., 2014 Advance Article). It is noteworthy that other highly-reactive nascent gases (such as Cl and N) may also be useful in CH (or CO) bond cleavage during graphene synthesis, yet these other elements appear to produce unavoidable hetero-atomic doping of the resultant graphene product surfaces.

[0078] In another embodiment, elements of non-inertial cavitation bubble production can be combined into elements of an inertial cavitation-inducing reactor (FIG. 9A). In one embodiment, miniature ultrasonic transducers (FIG. 9B) are incorporated or machined into the cavities (depressions/chambers) of a rotating cavitation-inducing drum within a cavitation reactor. The miniature ultrasonic transducer rods can be energized so as to deliver ultrasonic acoustic waves directly into the immediate area of cavitation bubble genesis and BH; an area where nanoparticle synthesis should be initiated in such embodiment. In yet another embodiment, a rotating cheese grater wheelakin to a commercial food processorcan be employed (as seen in FIG. 10) to induce multiple shearing cavitation flow events.

[0079] In another embodiment, electrodes capable of producing an electrical arc discharge can be incorporated into a hydrodynamic cavitation-inducing reactor chamber. The elements of the arc discharge electrodes are designed to produce a nanoparticle inducing electrical arc in the vicinity of cavitation bubble genesis and BH. The combined forces of the electrical arc discharge and the collapsing cavitation bubbles are believed to enhance nanoparticle synthesis and growth.

[0080] In another embodiment, electron (or other ionizing) radiation, laser or DUV light can be introduced into the hydrodynamic cavitation-inducing reactor chamber, with the combined forces believed to enhance production of nascent hydrogen (or other mono-atomic) gases useful in CH bond cleavage, CC cross-linking and subsequent self-assembly and growth of nanoparticles, PAHs, lacey carbon ribbons, graphene/GO sheets, etc. (see, for a non-hydrodynamic, non-cavitation, simple solid substrate-using example, Matei et al., Functional Single-layer Graphene Sheets from Aromatic Monolayers, Adv. Mater., Vol. 25, Issue 30, Aug. 14, 2013, p. 4145; see also Angelova et al., A Universal Scheme to Convert Aromatic Molecular Monolayers into Functional Carbon Membranes, ACS Nano, Vol. 7, Issue 8, 2013, pp. 6489-6497).

[0081] Synthesis of Graphene and its Derivatives in the Presence of Water

[0082] It is theorized that carbon radicals play an important role in the synthesis methods of the invention, regardless of the specific method employed to generate those carbon radicals from their carbonaceous starting materials. Likewise, it is theorized that water plays an equally important role in the formation of graphene from such carbon radicals.

[0083] When considering the so-called solute effect in water, the uniqueness of solute hydrophobic hydration in water must be considered. It is known that methane gas can become caged within frozen water. The product, methane hydrate (so-called fiery ice) can burn aflame in the palm of the hand. Methane gas is one of the syngas species commonly produced by embodiments of the invention. Methyl radicals (CH3) are sp2-hybridized, trigonal planar carbon radicals. The fact that CH3 is already sp2-hybridized carbon plays a part in the theorized interactions between carbon and water. It is theorized that carbon atoms (as carbonyl radicals) can interact (albeit, for fractions of picoseconds at a time) with the holes in so-called water cages in liquid water. It is believed that when water is perturbed to the point of becoming superheated or supercritical (an area of water's phase diagram where a triple-point exists), portions of the water in the reaction exist in several phases (liquid, gas, solid) simultaneously, and/or water exhibits some of the molecular structure characteristics of each and all of these phases simultaneously. Water is known to surround non-polar solutes in clathrate cages (FIG. 11).

[0084] It is theorized that during graphene synthesis in the presence of water, according to the methods of the invention, carbonyl ions become surrounded in water clathrate cages in a guest/host relationship. The carbonyl ions are believed to oscillate within the hole in the water cage, finding brief meta-stability as pseudo-methyl radicals at each end; the carbon's available electrons briefly exchanging temporary bonds with three hydrogen atoms found like fingers at each of the openings of the water hole (FIG. 12). With the (fractional picoseconds) progression of time, additional water/carbon clathrate cages interact with the first, building a chain of cages that eventually folds upon itself in a helix, highly analogous to the structure of water seen in the frozen ice phase (FIG. 13). Once in this hexagonal configuration, it is theorized that the carbons then participate in bonds with each other and precipitate out of the water as benzene rings or (in the case of multiple clusters of ring cages), small groups of rings comprising PAHs.

[0085] It is unknown whether methyl radicals shed hydrogen prior to encapsulation by water, or never had them (as a carbonyl radical) before interacting directly with water, thereby sharing associations (weak bonds) with the hydrogen of surrounding water molecules (attracted to the carbon radical by its charge and their own polarity) as the cage formations grow. If carbon radicals are involved individually in the synthesis of graphene sheets, it may be to heal defects of departing heteroatoms from the growing deoxygenated sheets. It has been shown that carbon radicals (in vapor form) introduced to defective graphene or GO sheets in solution, contribute to their self-healing and repair into nearly perfect or near pristine graphene exhibiting a six-fold increase in electrical conductivity and >96% transparency (see Boya Dai et al., High-quality single-layer graphene via reparative reduction of graphene oxide, Nano Res., Vol. 4, Issue 5, May 2011, pp. 434-439). Methods of the present invention are believed to produce such carbon radicals (as nascent vapor) in solution during graphene synthesis.

[0086] It has likewise been recently revealed that nascent hydrogen (as generated, in situ) can contribute significantly to the ionic reduction of aqueous solutions of GO into graphene (see Pham et al., Chemical reduction of an aqueous suspension of graphene oxide by nascent hydrogen, J. Mater. Chem., Vol. 22, 2012, pp. 10530-10536; see also, Pham et al., Electronic Supplementary Material (ESM), J. Mater. Chem., 2012 Royal Society of Chemistry, correcting earlier misconceptions regarding an electron-transport mechanism of chemical reduction of GO to graphene in solution via presumed adhesion of GO to the surfaces of the Zn or Al sheets; Domingues et al, Reduction of graphene oxide films on Al foil for hybrid transparent conductive film applications, Carbon, Vol. 63, 2013, pp. 454-459; see also Sofer et al., Highly hydrogenated graphene via active hydrogen reduction of graphene oxide in the aqueous phase at room temperature, Nanoscale, 2014, Advance Article).

[0087] It is especially noteworthy that elements of the present invention are believed to necessarily produce nascent hydrogen in situ (in aqueous solution) as part of the as-synthesized syngas during hydrothermal pyrolysis of carbonaceous feedstock to make graphene and its derivatives. These aforementioned recent studies serve to confirm the importance and efficacy of as-synthesized (newly formednascent) hydrogen ions in the synthesis of high-quality graphene and the deoxygenation (reduction) of any intermediate GO species into graphene. It is theorized that atomic hydrogen abstraction from reactive end-carbons of hydrogenated graphene sheets also permits hydrophobic self-assembly of graphene scales into large-area sheets. This, in contrast to coal and hydrogenous compound slurry ball milling techniques known to the art to also produce in situ molecular (H2) hydrogen, yielding amorphous hydrogenated ta-C and carbon/hydrogen clathrate species with no reported graphene or GO sheets (see U.S. Pat. No. 7,901,661 to Leuking et al.). In a related embodiment, the ball milling methods of Leuking et al., supra, may be modified by the addition of certain metallic oxide powders or nano-powders to yield novel SGANs (Surface-graphitized Abrasive Nanoparticles) for tribological and other uses. This, owing to the tendency (in some cases) of the Leuking et al., procedure to yield hydrogen trapped endohedral fullerenes; structures that theoretically could be made to comprise endohedral metallofullerenes with little additional procedural effort according to methods previously described by Shankman; namely, the addition of certain metallic oxides to the slurry.

[0088] Additionally, hydrogen ions are believed to be produced during spontaneous dissociation of water when perturbed to superheated or supercritical temperatures, according to methods of the present invention, including within the micro-environment of collapsing cavitation bubbles in aqueous solution. The importance of these mono-atomic hydrogen ions (H+) cannot be overlooked or under-emphasized when considering the MD of graphene synthesis in aqueous solution.

[0089] First-order molecular dynamics modeling at the University of Louisville (Louisville, Ky., U.S.A.) also showed that already-formed benzene rings (confined in a vacuum with hot water vapor) will cyclize into self-healing PAHs resembling graphene scales, in the absence of any metallic catalyst. The Louisville MD modeling would also appear to agree with elements of the earlier Loginova et al., modeling supra; in that carbon clusters, not individual atoms, participate in edge growth of graphenealthough quite different causal conclusions were reached in these two studies. The unique water-influenced self-healing phenomenon, as seen in the University of Louisville MD modelling, is believed to be invaluable to the synthesis of both high-quality graphene and large-area graphene sheets. The absence of a metallic substrate as a framework in the aforementioned University of Louisville MD modeling suggests that water (or its surface tension) alone is capable of acting as the necessary framework/agent for graphene nucleation and growth in hydrothermal, dehydration or aqueous synthesis conditions.

[0090] Recent studies suggest that the observed University of Louisville self-healing MD mechanism may be related to the so-called intramolecular cross-dehydrogenative coupling (ICDC) seen in rGO treated with FeCl3 at room temperature (see Park et al., Defect healing of reduced graphene oxide via intramolecular cross-dehydrogenative coupling, Nanotechnology, Vol. 24, No. 18, May, 2013, Article ID. No. 185604). This Park et al. study seems to reinforce the importance and efficacy of nascent hydrogen and possibly water (through its self-ionization/autoprotolysis ions H+, H3O+, OH) in the synthesis, growth and self-repair of the graphene matrix.

[0091] It has been observed that residual water remaining on a substrate during graphene formation can inversely cause so-called holey carbon or lacey carbon (graphene nanoribbons) to form. This phenomenon suggests that water may also be employed on substrates to control the amount and shape of graphene deposition, enabling the hydrophobic fashioning of circuit patterns on solids. This phenomenon may be employed to serve as water or ice etching of graphene sheets. These disclosed wet methods of graphene etching of the present invention are superior to recently described dry methods, in that the graphene edges may be functionalized with hydrogen (H), carbonyl (O), carboxyl (COOH), hydroxyl (OH), aldehyde (RCHO), carboxylate (RCOO) or ester (COOR) functional groups, or combinations thereof, in a one-step process during hydrothermal synthesis in aqueous solution according to embodiments of the invention, then introduced to water or ice masks or patterns on substrates to fashion circuit patterns or other intended designs or morphologies (see, in comparison, U.S. Patent Application No. 2013/0157034 by Choi et al.).

[0092] Elements of the invention reveal the special properties of water within the context of graphene synthesis. For example, it is believed that frozen water (ice) presents a novel substrate for epitaxial growth of large-area graphene sheets. Chilled water vapor can easily be applied to other solid substrates, then cooled to produce a layer of solid ice or frost upon which reactant vapor (produced according to the methods of the invention) may be deposited permanently, or temporarily to facilitate the recovery of graphene.

[0093] Additionally, it is possible to incorporate the carbonaceous precursor material (such as various polysaccharide solutions) directly into an aqueous substrate coating and once applied, thereafter dehydrate/pyrolyze the substrate coating via heating to produce a recoverable or permanent graphitic film (see, for example, U.S. Patent Application No. 2013/0209793 by Sanchez et al.).

[0094] In one embodiment, the water of the hydrophobic self-assembly pool can be temperature manipulated, including but not limited to a cycles of freezing and thawing the water, to encourage accelerated graphene formation through inducing corresponding changes in the structure and interaction of the water molecules therein. In another embodiment, audio waves, including those of acoustic levitation frequencies and strength, are used to encourage the liquid molecules in the synthesis apparatus and/or hydrophobic self-assembly pool to arrange in various geometric patterns (see generally, the phenomenon of the water-molecular hexagons of Cymatics; see also Su Zhao and Jrg Wallaschek, A standing wave acoustic levitation system for large planar objects, Archive of Applied Mechanics, Vol. 81, Issue 2, pp. 123-139, January 2011); Igor V. Smirnov, The effect of a Specially Modified Electromagnetic Field on the Molecular Structure of Liquid Water, Explore Issue, Vol. 13, No. 1, 2003).