WO2018100552A1

WO2018100552A1 - Manufacture of graphene materials using a cavitation reactor

Info

Publication number: WO2018100552A1
Application number: PCT/IB2017/057581
Authority: WO
Inventors: Don Edward Kress; Kamalul Arifin Yusof
Original assignee: CETAMAX VENTURES Ltd
Current assignee: CETAMAX VENTURES Ltd
Priority date: 2016-12-01
Filing date: 2017-12-01
Publication date: 2018-06-07
Anticipated expiration: 2019-06-01

Abstract

Devices, systems and methods for manufacturing graphene materials using a vortex reactor are disclosed. The vortex reactor is configured to receive a fluid mixture of two immiscible fluids. When directed into the reactor, the fluid mixture follows a vortical path that provides effective separation of the fluids and forms an interface between the fluids. Graphene flakes are generated through ultrasonic exfoliation of a graphite material, and the graphene flakes aggregate at the interface to form in a tube-shaped graphene sheet material.

Description

MANUFACTURE OF GRAPHENE MATERIALS

USING A CAVITATION REACTOR

BACKGROUND

[0001] The present disclosure relates generally to the manufacture of graphene materials, including tube-shaped graphene sheet materials and graphene-enhanced polymer composites.

[0002] Graphene is an atomic-scale, crystalline allotrope of carbon with carbon atoms densely packed in a regular two-dimensional hexagonal lattice structure. Certain graphene materials exhibit beneficial material properties, including extremely high electrical conductivity, heat conductivity, and strength to weight ratios, as well as unique optical characteristics.

[0003] One conventional technique for producing graphene involves "exfoliation" of bulk graphite to pull flakes away from the bulk graphite. Some techniques achieve exfoliation through reduction of a graphite oxide material. However, resulting flakes fail to exhibit the same degree of beneficial material properties as defect-free unoxidized graphene. Another technique utilizes sonication of a bulk graphite material, followed by centrifugation. While this technique achieves relatively high concentrations of graphene, restacking of individual graphene units into solid graphite forms is a recurrent issue.

[0004] Accordingly, there is a need for devices, systems, and methods for effectively producing graphene materials.

BRIEF SUMMARY

[0005] The present disclosure relates to the manufacture of graphene materials, including tube-shaped graphene sheet materials and graphene-enhanced polymer composites. In particular, the present disclosure describes embodiments which manufacture graphene materials by utilizing one or more vortex reactors to control fluid dynamics and provide desired processing conditions to enable effective formation of the graphene materials.

[0006] In some embodiments, a vortex reactor includes a reactor body having a first end and a second end. The reactor body includes one or more inlet ports disposed near the first end. The one or more inlet ports are configured to direct a reactor fluid into the reactor body. The one or more inlet ports can be tangentially oriented with respect to an inner surface of the reactor body so that the fluid mixture directed into the reactor body follows a vortical path as it rises within the reactor body toward the second end. [0007] In some embodiments, a base plate is attached to the reactor body at the first end. Disposed within the base plate are an ultrasound horn or array of ultrasound horns. One or more ultrasound horns are configured to impart ultrasound energy into the reactor body. In some embodiments, an exfoliation zone is provided between the one or more inlet ports and the ultrasound horn or array. The exfoliation zone can receive a graphite material and can function as a holding reservoir where the graphite material is maintained during operation of the reactor. Ultrasound energy from the ultrasound horn or array is directed at the graphite material to form graphene flakes via ultrasonic exfoliation, and at least a portion of the graphene flakes then migrate into the vortical path of the fluid mixture as it passes through the reactor.

[0008] During operation, a fluid mixture of two immiscible fluids is directed into the reactor. The vortical motion of the fluid aids in separating the fluids into an outer fluid and an inner fluid with an interface formed between the separated fluids. Graphene flakes aggregate at the interface and self-assemble into graphene sheets. The three-dimensional shape of the interface causes the resulting graphene sheets to form a tube-shaped structure. The tube-shaped graphene sheet may be collected and processed in one or more further downstream processes.

[0009] In some embodiments, a vortex reactor further includes an outlet pipe that extends upwards from the first end of the reactor body toward the second end. A guide cone is coupled to the upper end of the outlet pipe. When a fluid is advanced into the reactor body through one or more inlet ports at the first end, the fluid flows in an outer vortex along an inner surface of the reactor body for a distance toward the second end. after reaching an apex, the fluid then reverses direction to flow into the guide cone and down through the outlet pipe. A second ultrasound horn or array may be positioned at the second end with one or more ultrasound horns extending toward the guide cone so as to impart ultrasound energy to the fluid mixture as it crests over the guide cone and into the outlet pipe. One or more injectors may also be positioned to enable delivery of a polymerizing agent and/or additive into the reactor within the vicinity of the guide cone. During operation, a mixture of two immiscible fluids and graphene flakes follows the outer vortical path upwards until reaching an apex near the second end of the reactor. The mixture then moves radially inward and crests over the guide cone and then down into the outlet pipe. Near the apex, energy imparted by the second ultrasound horn or array and fluid dynamics at the apex cause the immiscible fluids to form an emulsion (preferably water in oil). The graphene within the mixture aggregates at the plurality of interfacial regions between the immiscible fluids of the emulsion. Where one of the immiscible fluids is polymerizable, polymerization of the polymerizable fluid forms a porous polymer that traps the other fluid within the cavities/pores of the resulting structure, with the graphene remaining at the interface as a coating of the cavities/pores. The other fluid may then be evaporated leaving a porous graphene polymer composite material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] To further clarify the above and other advantages and features of the present disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only illustrated embodiments of the disclosure and are therefore not to be considered limiting of its scope. Embodiments of the disclosure will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0011] Figure 1 illustrates an exemplary embodiment of a reactor configured to generate a single vortex;

[0012] Figure 2 illustrates an exemplary embodiment of a reactor configured to generate dual vortices;

[0013] Figure 3 illustrates an exemplary embodiment of a reactor having a collection assembly for collecting different components from different radial separation zones;

[0014] Figures 4 and 5 illustrate exemplary embodiments of a vortex reactor configured to generate tube-shaped graphene sheets;

[0015] Figure 6 illustrates an exemplary embodiment of a process flow for producing tube-shaped graphene sheets using, for example, a vortex reactor as in Figure 4 or Figure 5;

[0016] Figure 7 illustrates an exemplary embodiment of a vortex reactor configured to generate a graphene-enhanced polymer composite;

[0017] Figure 8 illustrates an exemplary embodiment of a process flow for producing graphene-enhanced polymer composites using the vortex reactor of Figure 7; and

[0018] Figure 9 illustrates an alternative embodiment of a process flow for producing graphene sheets using, for example, a vortex reactor as in Figure 4 or Figure 5.

DETAILED DESCRIPTION

Introduction

[0019] The present disclosure relates to devices, systems, and methods for producing graphene sheets and/or graphene-enhanced composite materials using one or more vortex reactors. At least some of the vortex reactor embodiments described herein may be utilized to effectively manufacture graphene sheet materials and/or graphene-enhanced composite materials by providing a vortical tubular interface between two immiscible fluids where graphene flakes can self-assemble to form a graphene sheet material.

[0020] "Graphene sheets" generated using the embodiments described herein can have a thickness of less than or equal to about four or five carbon atoms, and may also be referred to as "few layer graphene" or "FLG." It is at these thicknesses that the beneficial properties of graphene emerge, whereas thicknesses greater than about five carbon atoms typically cause the material to lose beneficial properties of graphene and begin to exhibit more graphite-like properties.

[0021] Flakes of graphene may be trapped at an interface between two immiscible fluids where a resulting graphene sheet may be formed. U.S. Patent Application Publication No. 2014/0305571, which is incorporated herein by reference in its entirety, describes a process whereby graphene flakes are introduced into a phase separated system. The kinetics of the system cause the graphene to self-assemble at the interface between two immiscible fluids, where the flakes layer together to form graphene sheets.

[0022] The embodiments described herein beneficially provide one or more of effective formation, processing, collection, or yield of such graphene sheets by utilizing at least one vortex reactor to form a vortical tubular interface between two immiscible fluids to enable effective self-assembly of the graphene sheets at the interface. Some embodiments also include one or more components for generating graphene flakes from a graphite source material. The graphene flakes are generated in-situ within the vortex reactor where they can subsequently self-assemble into graphene sheets as they pass through the reactor.

[0023] In addition, graphene may be utilized to form stabilized composite materials by mixing the graphene in an emulsion of immiscible fluids, allowing the graphene to stabilize the emulsion by aggregating at the various fluid interfaces of the emulsion, and polymerizing one of the fluids to form a matrix having cavities lined with graphene. Such a process is described by U.S. Patent Application Publication No. 2015/0348669, which is incorporated herein by reference in its entirety. At least some of the vortex reactor embodiments described herein enable effective generation of such graphene-enhanced composite materials by providing one or more of effective mixing, emulsion formation, fluid interface control, or other fluid dynamics enhancements. [0024] Although preferred vortex reactor embodiments for processing graphene are described herein, other exemplary vortex reactor configurations which may be utilized to effectively process graphene are described in U.S. Patent Application No. 15/170,298, which is incorporated herein by reference in its entirety.

Overview of Vortex Reactor Configurations

[0025] Figure 1 illustrates an embodiment of a vortex reactor 100 configured to form a single vortex during operation of the reactor. The illustrated embodiment includes one or more inlet ports 102 disposed at a first end 104 of vortex reactor 100. The illustrated inlet ports 102 open into a reactor body 108 configured to contain a reactor fluid mixture which is directed into vortex reactor 100 through the inlet ports 102. In the illustrated embodiment, the reactor body 108 has a circular cross-section. Other embodiments can include a triangular, square, rectangular, or other polygonal shaped cross-section, or an ellipsoid or ovoid cross-section. The illustrated reactor body 108 has a cylindrical shape with substantially uniform diameter along its height. In other embodiments, the reactor body 108 can have a non-uniform diameter along its height, such as a conical shape with a diameter at a second end 106 that is narrower than a diameter at a first end 104 (or vice versa).

[0026] As illustrated, inlet ports 102 are oriented so as to receive the reactor fluid mixture at an angle that is tangential or substantially tangential to an inner surface of the reactor body 108. The orientation of the inlet ports 102 causes the incoming fluid to form a vortex as it advances into reactor body 108. The generated vortex causes the fluid mixture to be subjected to centripetal and centrifugal forces along the trajectory of the vortex. Additionally, or alternatively, reactor 100 can include a pump, turbine and/or impeller assembly, or other fluid movement means configured to form and/or strengthen the vortex.

[0027] The illustrated embodiment includes two inlet ports 102 disposed at the first end 104. Other embodiments may include one inlet port or may include more than two inlet ports. In the illustrated embodiment, the first end 104 and the associated inlet ports 102 are disposed at the bottom of a vertically oriented reactor body 108, and the vortex that results from reactor operation therefore rises vertically toward the second end 106. In other embodiments, one or more inlet ports may be disposed on an upper end of a vertically oriented reactor body, allowing for a downflow vortex during operation of the reactor. In yet other embodiments, a reactor body may be oriented horizontally, or diagonally, and one or more inlet ports can be configured to provide a horizontally or diagonally moving vortex. The orientation of the reactor 100 with respect to gravity may therefore be configured according to preferences and/or particular application needs.

[0028] In the illustrated embodiment, the one or more inlet ports 102 are configured to deliver fluid at an angle that is tangential to the inner surface of the reactor body 108. The illustrated inlet ports 102 are angled to be substantially perpendicular to a longitudinal axis of the reactor 100 (i.e., are not angled upwards toward second end 106 or downwards toward the first end 102). In other embodiments, one or more of the inlet ports 102 are configured to deliver fluid at an upward angle or downward angle (e.g., at an angle opening toward second end 106 or toward first end 102). The angle at which an inlet port is directed can be adjusted to provide one or more desired features to fluid flow within the reactor 100. For example, relatively higher inlet angles can generate a vortex that has a lower angular velocity and which rises to the second end 106 in less relative time. On the other hand, relatively lower inlet angles can generate a vortex that has a higher angular velocity and which rises toward the second end 106 in more relative time. Such angles can advantageously alter the fluid dynamics within the reactor to provide desired pressures, mixing effects, and/or other fluid flow dynamics.

[0029] In embodiments where a plurality of inlet ports 102 are included, the tangentially arranged inlet ports 102 may be configured so that at least one inlet port is asymmetrically aligned with at least one other inlet port to provide beneficial mixing of inflowing reactor fluid in at least the initial inflow region of the reactor 100. Such asymmetrical alignment provides a more turbulent initial flow, allowing advantageous mixing and/or graphene flake dispersion to occur in at least the initial inflow region (e.g., region near the inlet ports 102) of the reactor 100. Subsequently, as the reactor fluid mixture continues to flow toward the outlet 114 at the second end 106, the fluid will self- organize into a relatively more structured vortical flow beneficial for creating an interface for controlling graphene flake movement and associated graphene sheet formation.

[0030] The illustrated vortex reactor 100 also includes a bleed opening 110 disposed at or near second end 106. In other embodiments, bleed opening 110 can be disposed at or near first end 104 (e.g., in downflow configurations). In the illustrated embodiment, bleed opening 110 is configured to bleed off air or other gases and/or liquids that may be present in reactor body 108 prior to advancing a reactor fluid mixture into the reactor 100. Bleed opening 110 may be formed as a hole, slit, valve, or other suitable controllable fluid passageway. In some embodiments, the bleed opening 110 is configured as a valve, such as a one-way valve allowing the passage of fluid out of the reactor but not into the reactor. In some embodiments, the bleed opening 110 is configured as a valve allowing the passage of air or other gas out of the reactor but preventing the passage of liquid out of the reactor.

[0031] The illustrated reactor 100 includes a vortex outlet 114 disposed at the second end 106. In some embodiments, the vortex outlet 114 can extend from second end 106 a distance into reactor body 108 (e.g., as a pipe or conduit extending into reactor body 108). In the illustrated embodiment, the vortex outlet 114 is substantially aligned with the longitudinal axis of reactor 100, though other embodiments may include an off-center vortex outlet 114.

[0032] Preferably, the reactor 100 omits internal baffles and/or other obstructing structures, allowing fluid flow through the reactor to self-organize into a vortex. The illustrated reactor 100 also includes a set of wall ports 130. One or more of such wall ports 130 may be utilized as outlet ports for conducting a portion of the fluid mixture out of the reactor. Alternatively, one or more of such wall ports 130 may be utilized for introducing solids, fluids, or mixtures into the reactor at one or more desired locations along the vortical fluid path within the reactor body 108.

[0033] Figure 2 illustrates an embodiment of a vortex reactor 200 configured to generate dual vortices during operation of the reactor 200. Except where specifically described otherwise, components of the vortex reactor 200 may be configured as counterpart components of the vortex reactor 100 of Figure 1. The illustrated embodiment includes one or more inlet ports 202 disposed at the first end 204. The inlet ports 202 open into a reactor body 208 configured to receive fluid directed through the inlet ports 202.

[0034] In the illustrated embodiment, one or more of the inlet ports 202 are oriented to direct fluid at an angle that is tangential, or substantially tangential, to an inner surface of reactor body 208. This configuration allows the fluid to form an outer vortex 216 as it advances through the reactor body 208 toward the second end 206. The outer vortex 216 subjects the fluid within the reactor to centripetal and centrifugal forces along the trajectory of outer vortex 216.

[0035] The illustrated reactor 200 also includes a bleed opening 210 to function as a valve for modulating passage of fluid within the reactor body 208. The illustrated reactor 200 also includes a vortex outlet 214 disposed at the first end 204 of the reactor. In the illustrated embodiment, the vortex outlet 214 extends from the first end 204 a distance into reactor body 208. The illustrated vortex outlet 214 is aligned with a longitudinal axis of the reactor 200. As shown, the inlet ports 202 may be arranged in a radial pattern around the vortex outlet 214.

[0036] In operation, the outer vortex 216 axially advances toward the second end 206. Upon reaching the second end 206, the fluid mass reverses axial/longitudinal direction to travel back down to first end 204 in an inner vortex 218 as it advances toward the vortex outlet 214.

[0037] Figure 3 illustrates an embodiment of a vortex reactor 801 having a second end 806 configured to separate different fractions of the fluid mass according to different radial zones in which the different fractions accumulate. For example, the vortical motion of the fluid as it moves toward the second end 806 will cause lower density fractions to concentrate closer to the axis of the vortex, while fractions of progressively greater density will concentrate at positions extending radially outward from the axis. As shown, a series of outlet members 822 are arranged at different radial separation zones, and may be positioned to separately receive different fractions of the fluid mass passing through the reactor 801.

[0038] The illustrated configuration may be utilized with any of the reactor embodiments described herein to enable effective collection and separation of the different components formed in a graphene sheet production process. For example, when two immiscible fluids are passed into the vortex reactor, the vortical motion of the fluid mixture aids in effectively separating the two fluids as they rise from the first end to the second end, enabling the formation of a tubular fluid interface, with the less dense fluid disposed radially closer to the axis and the other denser fluid disposed radially closer to the periphery. Where sufficient generated graphene flake material is provided within the reactor, the generated graphene flakes will accumulate at the interface and self-assemble to form a continually rising tubular graphene sheet.

[0039] The separate outlet members 822 can be radially positioned to coincide with the different separation regions of the fluid mass. For example, one outlet member may coincide with the more peripheral fluid, another outlet member may coincide with the more central fluid, and another outlet member may coincide with the interface between the two fluids where the generated graphene sheet structure is disposed.

[0040] The outlet members 822 may be configured as outlet tubes, channels, conduits, or the like. In some embodiments, an outlet member may be formed as or may include a substrate for associating with the corresponding fraction of the fluid mass as it contacts the outlet member. For example, the outlet member corresponding to the interface position may be formed as or may include a substrate configured to associate with and aid in the collecting of the generated graphene sheet. In some embodiments, the substrate is a hydrophilic material such as a hydrophilic glass.

[0041] In the illustrated embodiment, the outlet members 822 are positioned at different radial zones and at different elevations within the reactor 801. Positioning the outlet members 822 at different elevations and/or at different tangential angles to the longitudinal axis enables the outlet members 822 to function with minimal disturbance to the vortical flow within the reactor 801. The illustrated embodiment also includes a central outlet 821 where the least dense fraction of the fluid mixture may exit.

Manufacture of Graphene Sheets

[0042] Figure 4 illustrates an exemplary embodiment of a vortex reactor 400 which may be utilized to effectively manufacture a tube-shaped graphene sheet material. In Figure 4, a section of the reactor wall has been cutout to better illustrate an interior portion of the reactor 400. Except where specified otherwise, the illustrated reactor 400 may include similar components and may be configured in a manner similar to that of foregoing reactor embodiments, and in particular in a manner similar to the single vortex reactor of Figure 1.

[0043] The illustrated reactor 400 is configured as a single vortex reactor having an array of one or more inlet ports 402 oriented to generate upwardly rising vortical motion in the incoming fluid. In preferred embodiments, a mixture of two immiscible fluids is directed into the reactor 400 through inlet ports 402. In some embodiments, a first fluid is water and a second fluid is a suitable solvent immiscible with water. In some embodiments, the first fluid is water and the second fluid is a suitable immiscible oil. Fluids utilized in the reactor may be selected based on preferences and/or particular application needs. In one presently preferred embodiment, the immiscible fluid mixture includes water and heptane. Much of the following description is given in the context of a water and heptane embodiment. However, it will be understood that the same concepts apply to alternative embodiments utilizing alternative fluid mixtures.

[0044] The volumetric ratio of fluids used will determine at what radial distance from the longitudinal axis the interface between the two fluids will form. For example, a greater proportion of the fluid which migrates to the periphery will move the interface radially inward, while a greater proportion of the fluid which migrates radially inward will push the interface radially outward. The ratio of the fluids of the fluid mixture may therefore be adjusted to the preferred ratio in order to achieve desired interface size, shape, and position.

[0045] The fluid mixture may be directed to the reactor 400 in a pre-mixed form. Alternatively, the reactor 400 may be operated to provide the mixing of the separate fluids. For example, one inlet port or set of inlet ports may be utilized to direct the first fluid into the reactor 400 while another inlet port or set of inlet ports may be utilized to direct the second fluid into the reactor 400.

[0046] In operation, the fluid mixture is directed into the reactor 400 and vortical flow results. Centripetal and centrifugal forces aid in separating the separate phases of the fluid mixture. The denser phase (e.g., water) reports to the peripheral volume of the reactor, closer to the reactor wall, while the less dense phase (e.g., heptane) reports to the inner volume of the reactor, closer to the longitudinal axis of the reactor. As the interface between the separate fluids forms, graphene flakes within the system will aggregate at the interface, enabling the formation of a tube-shaped graphene sheet material.

[0047] In preferred embodiments, the graphene flakes are generated in-situ within the reactor 400. The illustrated embodiment includes an exfoliation zone 432 disposed near the first end 404 above one or more ultrasound horns 434, where graphene flakes are generated from a mass of graphite particles disposed within the exfoliation zone 432. The graphite particles may be directed into the exfoliation zone 432 through one of the inlet ports 402 (either through a shared port with one or both fluids or through a dedicated port).

[0048] The exfoliation zone 432 is provided as a space between the inlet ports 402 and the base plate 436 in which the ultrasound horn or array 434 is disposed. This space provides a holding area for the graphite where it can receive ultrasound sonication without being overly caught up in the vortical fluid motion. In some embodiments, the exfoliation zone 434 has a height that is about 30%, 20%, 10%, 5%, or 1% of the overall height of the reactor body 408, or has a height that is within a range defined by any two of the foregoing percentages.

[0049] As shown, the reactor 400 includes an ultrasound horn or array 434 of ultrasound horns for imparting sufficient ultrasound energy to the graphite particles within the exfoliation zone 432. The ultrasound energy imparted to the graphite particles forms graphene flakes via ultrasonic exfoliation. In the illustrated embodiment, the ultrasound horn or array 434 is arranged in a base plate 436 of the reactor. Alternative embodiments may position one or more ultrasound horns at different locations, such as within the wall of the reactor. During operation of the reactor, the graphite particles swirl around within the exfoliation zone 432 just above the ultrasound horn or array 434. As the graphene flakes are formed, they will tend to aggregate at the interface between the phases of immiscible fluids as the immiscible fluids coalesce into separate phases while rising in the reactor 400 toward the second end 406. The formed graphene sheet and the separate fluids may then be collected from the reactor.

[0050] Figure 5 illustrates another embodiment of a vortex reactor 500 which may be utilized in a graphene sheet production process. The embodiment shown in Figure 5 is similar to the embodiment shown in Figure 4. However, the reactor wall of the illustrated reactor 500 has a conical shape, with the diameter at the second end 506 being smaller than at the first end 504. Alternative embodiments may have a conical shape with the smaller diameter disposed at the first end 504. However, where a conical shape is utilized it is preferred that the smaller diameter end be disposed at the second end 504. This configuration causes the angular velocity of the fluid mixture to beneficially increase as the fluid mixture rises in the reactor, thereby enhancing phase separation effects and associated graphene sheet aggregation.

[0051] Figure 6 illustrates an exemplary process flow 600 by which a tubular-shaped graphene sheet material may be produced. As shown, the process flow 600 includes a vortex reactor 601. The vortex reactor 601 may represent any of the vortex reactor embodiments described herein. In preferred embodiments, the vortex reactor 601 is similar to a vortex reactor as shown in Figure 4 or 5. The illustrated embodiment combines a water stream 638 and a heptane stream 640 to form the reaction fluid mixture 642. As shown, a suitable pump 644 drives flow of the fluid mixture into the reactor 601, where it is combined with a graphite stream 646 at the initial inflow region of the reactor 601 (i.e., the exfoliation zone 648). The illustrated ultrasound horn or array of horns 634 impart ultrasound energy to the graphite material at a level sufficient to generate graphene flakes via ultrasonic exfoliation of the graphite material.

[0052] As shown, operation of the vortex reactor 601 outputs a process stream 650 including the generated tube-shaped graphene sheet along with the water and heptane. The process stream 650 is then routed to one or more downstream processes 652. In some embodiments, the generated graphene sheet material is cut, sliced, and/or otherwise formed into a threaded shape, which may be wound, spooled, or otherwise stored as a graphene thread or string product. Such a product may be utilized by weaving into fabric or other useful material, for example. Additionally, or alternatively, the tube-shaped graphene sheet material may be sliced (e.g., in a helical fashion) to form a ribbon shape. The ribbon may then be wound onto a spool or otherwise suitably arranged for use as a graphene ribbon product.

[0053] The illustrated one or more downstream processes 652 include water and/or heptane recycling process steps to generate a recovered water stream 654 and a recovered heptane stream 656. As shown, water and heptane makeup may be added as needed to maintain desired mass balances, fluid ratios, and process flow operability.

[0054] The vortex reactor 601 may be operated in a continuous fashion with continuous collection of generated graphene sheet material. In some implementations, the reactor 601 is operated in a semi-batch mode, with fluids continuously fed and recycled as needed while a tubular-shaped graphene sheet is formed and then ejected, with the process repeated as desired. Other embodiments may include operation in batch mode.

[0055] Although the particular embodiment shown in Figure 6 utilizes heptane and water as immiscible fluids, it will be understood that other combination of immiscible fluids suitable for particular process needs may be used. For example, heptane may be replaced or combined with another non-polar liquid, such as another non-polar organic solvent, and water may be replaced or combined with another polar liquid, such as an alcohol, ammonia, acetone, etcetera.

[0056] Figure 9 illustrates an alternative process flow 900 by which a graphene sheet material may be produced. The vortex reactor 901 may represent any of the vortex reactor embodiments described herein. In preferred embodiments, the vortex reactor 901 is similar to a vortex reactor as shown in Figure 4 or 5. The illustrated embodiment combines a water stream 938 and a heptane stream 940 to form the reaction fluid mixture 942. As shown, a suitable pump 944 drives flow of the fluid mixture into the reactor 901, where it is combined with a graphite stream 946 at the initial inflow region of the reactor 901 (i.e., the exfoliation zone 948). The illustrated ultrasound horn 934 imparts ultrasound energy to the graphite material at a level sufficient to generate graphene flakes via ultrasonic exfoliation of the graphite material. Other embodiments may include additional ultrasound horns. For example, a plurality of ultrasound horns may be arranged in an array near the exfoliation zone 948.

[0057] The output stream from the vortex reactor 901, which includes a mixture of water, heptane, and graphene, is routed to a mixer 949. The mixer 949 is configured to provide sufficient shearing or mixing to form an unstable emulsion (i.e., an emulsion that will phase separate) of graphene coated spheres. Any mixing device capable of forming the emulsion may be utilized. One example of a suitable mixer is a high-shear mixer having a vortex induction mechanism as disclosed in U.S. Patent Application Publication No. 2016/0346758, which is incorporated herein by reference in its entirety.

[0058] The emulsion is then routed from the mixer 949 to a trough 951. The trough 951 may be any suitable structure that allows phase separation of the emulsion as the fluid moves, in laminar flow, from the inlet side to the outlet side of the trough 951. As the components of the emulsion separate within the trough 951, van der Waals attraction will cause the graphene sheets enveloping the fluid spheres to spread out at the interface layer and self-assemble into a continuous sheet. Thus, as the mass of fluid moves from the inlet side toward the outlet side, the trough 951 functions as an "extruder" of the coalesced graphene sheet. In some embodiments, process conditions such as flow rate through the trough 951 are calibrated to produce a graphene sheet having a width substantially equal to the width of the trough 951.

[0059] After being formed in the trough 951, the graphene sheet may be collected on a suitable receiving substrate. In the illustrated embodiment, a spool 953 is positioned near the trough 951 to wind and collect the graphene sheet. Other embodiments may additionally or alternatively utilize other collection means, such as a scraper plate, collection tray, rotating disk device, or the like. As described above, the collected graphene sheet may also be cut into a threaded or ribbon shape.

[0060] As with embodiments described above, the process 900 may also include water and/or heptane recycling steps to generate a recovered water stream 954 and a recovered heptane stream 956. Water and/or heptane makeup may be added as needed to maintain desired mass balances, fluid ratios, and process flow operability. The process 900 may be operated in a continuous fashion with continuous collection of generated graphene sheet material. Other implementations may be operated in batch or semi-batch mode. Further, as described above, other embodiments may utilize other suitable combinations of immiscible fluids. For example, heptane may be replaced or combined with another non- polar liquid, such as another non-polar organic solvent, and water may be replaced or combined with another polar liquid, such as an alcohol, ammonia, acetone, etcetera

Manufacture of Graphene-Enhanced Composites

[0061] One or more vortex reactors described herein may also be utilized for processing graphene to form a graphene-enhanced composite material. Figure 7 illustrates a vortex reactor 700 configured as a dual vortex reactor. The illustrated reactor has a substantially cylindrical shape, though it may have an alternative shape, such as a conical shape similar to the embodiment of Figure 5 or other reactor body shape described herein. The reactor 700 includes an inlet port assembly 702 disposed at a first end 704. The inlet port assembly 702 is configured to form an outer vortex when a fluid mixture is directed into the reactor. The outer vortex rises to the second end 706 of the reactor, where it then passes radially inward into a guide cone 758 and is directed downward in an inner vortex through an outlet pipe 714 that exits the reactor at the first end 704.

[0062] In preferred embodiments, the fluid mixture includes two immiscible fluids, with at least one of the immiscible fluids being a polymerizable fluid. Any desired combination of polymerizable fluid and at least one additional immiscible fluid may be utilized according to particular application needs, desired end product composition, and the like. In one presently preferred embodiment, the fluid mixture includes styrene and water. Other suitable polymerizable monomers that may be included in at least one phase of the fluid mixture include isoprene, butyl acrylate, divinylbenzene, methyl acrylate, tetra(ethylene glycol) diacrylate, and butyl methacrylate, for example.

[0063] The illustrated reactor 700 includes a first ultrasound horn or array 734 of one or more ultrasound horns disposed in a base plate 736 at the first end 704. In a manner similar to that described by the foregoing, a mass of graphite particles is input into the reactor at an exfoliation zone 732 disposed above a first ultrasound horn array 734. Ultrasound exfoliation of the graphite causes the formation of graphene flakes, which are carried upwards in the outer vortex of the fluid while self-assembling at the interface between the separate fluids.

[0064] Because the reactor is substantially closed at the second end 706, the fluid reaching the second end 706 is directed radially inward into the guide cone 758 and then downward into the outlet pipe 714. These structures assist in creating the emulsion required for manufacturing a graphene-enhanced, porous composite material. As the two immiscible fluids and the graphene crest over the rim of the guide cone, a high shear zone is created which aids in dispersing fine droplets (e.g., water droplets) within the continuous phase of the monomer. The relative proportions of the reactor diameter and the guide cone diameter may be adjusted to determine the angular velocity at which the emulsion is formed at the crest of the guide cone.

[0065] As shown, a second ultrasound horn or array 760 is positioned at the second end 706. In the illustrated embodiment, a second ultrasound horn or array 760 consists of a single ultrasound horn extending into the guide cone 758 at a distance to maximize the ultrasound energy imparted to the passing fluid vortex. Alternative embodiments may include additional ultrasound horns as part of the second ultrasound array 760 and/or can vary the relative depth of the ultrasound horn with respect to the guide cone 758.

[0066] In operation, as the fluid mixture reaches the second end 706, the fluid phases and the graphene will crest over the top edge of the guide cone 758 to be exposed to angular acceleration, shear forces, and ultrasound energy (and associated cavitation bubble formation and collapse) imparted by the second ultrasound array 760. The conditions at this region of the reactor can be tailored to generate an emulsion having desired characteristics. As the emulsion is formed, the graphene within the mixture will assemble at the interface of the formed emulsion droplets to stabilize the emulsion. For example, graphene will aggregate at the interfacial periphery of water droplets formed within another immiscible fluid (e.g., a styrene or styrene-based fluid) to form a graphene stabilized emulsion.

[0067] The illustrated embodiment includes a set of injectors 762 disposed at the second end 706 for injecting one or more suitable polymerizing agents into the fluid mixture at the region where the emulsion is formed. One or more of such injectors 762 may be utilized. The polymerizing agent(s) then pass with the emulsified mass through the outlet pipe 714. The emulsified mass may be sent to one or more downstream processes for generating a graphene-enhanced composite material. For example, the emulsified mass may be sent to one or more molds to allow polymerization and formation of the composite. In one example, the polymerizable fluid forms a polymer having a porous structure formed by the droplets of the other fluid. The graphene remains at the surface of the formed cavities, providing enhanced material properties to the composite material. The fluid forming the droplets (e.g., water) may be removed through drying, leaving graphene coated voids/pores behind.

[0068] The reactor 700 may also include one or more wall ports (not shown here, see corresponding structure of Figure 1) for introducing one or more fluids, additives, or other materials into the fluid mixture prior to emulsification and/or contact with any polymerizing agents. For example, one presently preferred embodiment utilizes a wall port to introduce an additive including poly(3,4-ethylenedioxythiophene) poly(styrene- sulfonate) ("PEDOT:PSS") to the outer vortex of the fluid mixture. The PEDOT:PSS is left behind after polymerization to form a conductive coating on the inside surfaces of the composite voids/pores.

[0069] Figure 8 illustrates an exemplary process flow 300 for producing a graphene- enhanced composite material using a vortex reactor 301. The vortex reactor 301 is configured similar to the vortex reactor 700 shown in Figure 7. As shown, streams of immiscible fluids, which in this example include a styrene stream 340 and a water stream 338 are mixed to form the reaction fluid mixture 342. As shown, a suitable pump 344 drives flow of the fluid mixture into the reactor 301, where it is combined with a graphite stream 346 at the initial inflow region of the vortex reactor 301 (i.e., the exfoliation zone 348). The illustrated array of ultrasound horns 334 impart ultrasound energy to the graphite material to generate graphene flakes.

[0070] Operation of the reactor 301 causes the fluid mixture to flow upwards in an outer vortex and then to pass into the guide cone 358, where ultrasound energy from the ultrasound horn 360 and one or more polymerizing agents from injectors 362 are applied to the fluid mixture. The resulting emulsion then passes down outlet/exit pipe 314, where it may be routed for further downstream processing. Additives may be optionally injected through wall port 330.

[0071] Elements described in relation to any embodiment depicted and/or described herein may be combinable with elements described in relation to any other embodiment depicted and/or described herein. For example, components of the process 600 shown in Figure 6 may be combined with components of the process 900 shown in Figure 9, and vice versa. The present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.

Claims

CLAIMS What is claimed is:

1. A vortex reactor for manufacturing a graphene material product, the vortex reactor comprising:

a reactor body having a first end and a second end;

a first ultrasound horn or array of ultrasound imparting devices disposed at the first end of the reactor body and configured to impart ultrasound energy into the reactor body; one or more inlet ports disposed above the first ultrasound horn or array and configured to direct the fluid into the reactor body so that the fluid rises from the one or more inlet ports toward the second end, the one or more inlet ports being tangentially oriented with respect to an inner surface of the reactor body so that the fluid directed into the reactor body follows a vortical path as the fluid rises toward the second end; and

an outlet configured to receive and pass the fluid out of the reactor body, wherein an exfoliation zone is provided between the one or more inlet ports and the first ultrasound horn or array, the exfoliation zone being configured for receiving a graphite material to enable the first ultrasound horn or array to impart ultrasound energy to the graphite material.

2. The vortex reactor of claim 1, further comprising an outlet pipe extending upwards from the first end to a position within the reactor body between the first end and the second end, and further comprising a guide cone coupled to the outlet pipe at an upper end of the outlet pipe, wherein advancing the fluid into the reactor body through the one or more inlet ports causes the fluid to flow in an outer vortex along an inner surface of the reactor body a distance toward the second end before the fluid reverses direction to flow into the guide cone and down the outlet pipe.

3. The vortex reactor of claim 2, wherein the outlet pipe and the guide cone are substantially aligned with a longitudinal axis of the reactor body.

4. The vortex reactor of claim 2 or claim 3, further comprising one or more injectors configured to deliver a polymerizing agent or additive into the reactor body at a region where the fluid crests over the guide cone to reverse direction and pass down the outlet pipe.

5. The vortex reactor of any one of claims 2 through 4, further comprising a second ultrasound horn or array of one or more ultrasound imparting devices disposed at the second end and extending toward the guide cone.

6. The vortex reactor of claim 1, wherein the outlet is disposed at the second end.

7. The vortex reactor of any one of claims 1 through 6, wherein the reactor body has a substantially cylindrical shape.

8. The vortex reactor of any one of claims 1 through 7, wherein the reactor body has a conical shape.

9. The vortex reactor of claim 8, wherein the conical shape has a narrower diameter at the second end than at the first end.

10. The vortex reactor of any one of claims 1 through 9, wherein the one or more inlet ports are oriented to be transverse to a longitudinal axis of the reactor.

11. A method of manufacturing a graphene sheet material, the method comprising: providing a vortex reactor according to any one of claims 1 through 10;

directing a fluid mixture into the vortex reactor so that the fluid mixture follows a vortical path through the vortex reactor, the fluid mixture including two immiscible fluids, the vortical path of the fluid mixture aiding in separating the two immiscible fluids to form an interface between the two immiscible fluids;

providing a graphite material within the vortex reactor;

imparting ultrasound energy to the graphite material sufficient to generate graphene flakes; and

the graphene flakes aggregating at the interface between the two immiscible fluids to form a graphene sheet material.

12. The method of claim 11, wherein the graphene sheet material has a tubular shape.

13. The method of claim 11 or claim 12, wherein one of the two immiscible fluids is water or is water based.

14. The method of any one of claims 11 through 13, wherein one of the two immiscible fluids is an alkane.

15. The method of claim 14, wherein the alkane is heptane.

16. The method of any one of claims 11 through 16, wherein the graphene sheet material has an average thickness of five carbon atoms or less.

17. The method of claim 16, wherein the graphene sheet material has an average thickness of four carbon atoms or less.

18. The method of any one of claims 11 through 17, further comprising processing the graphene sheet material by cutting the sheet to form a thread, string, or ribbon graphene material.

19. The method of any one of claims 11 through 18, wherein the vortex reactor is operated in a continuous mode by continuously extracting formed graphene sheet materials.

20. The method of any one of claims 11 through 18, wherein the vortex reactor is operated in a batch or semi-batch mode by fully forming each graphene sheet within the reactor prior to ejecting the formed graphene sheet from the reactor.

21. A method of manufacturing a graphene-enhanced composite material, the method comprising:

providing a vortex reactor according to any one of claims 2 through 10;

directing a fluid mixture into the vortex reactor so that the fluid mixture follows an outer vortical path upwards through the vortex reactor to an apex and then reverses direction to pass downward through an outlet pipe, the fluid mixture including two immiscible fluids and a plurality of graphene flakes, at least one of the fluids being polymerizable;

imparting ultrasound energy to the fluid mixture and graphene flakes at the apex to form an emulsion, the graphene flakes aggregating at the interfacial regions between the two immiscible fluids of the emulsion; and

injecting a polymerizing agent into the emulsion at the apex.

22. The method of claim 21, further comprising allowing the polymerizable fluid to polymerize, trapping at least a portion of the graphene to form a graphene-enhanced composite material.

23. The method of claim 21 or claim 22, further comprising providing a graphite material within the vortex reactor and imparting ultrasound energy to the graphite material to form the graphene flakes.

24. The method of any one of claims 21 through 23, further comprising passing the emulsion to one or more molds to carry out the polymerization.

25. The method of any one of claims 21 through 24, wherein the polymerizable fluid includes styrene.