Device and method for continuous synthesis of graphene

Abstract

Provided herein is a method and device for continuous graphene synthesis, the device including: a container having a space for holding a carbon source, the container having an inlet opening for receiving the carbon source material; at least two electrodes for applying a current through the space for Joule heating the carbon source, the space for Joule heating the carbon source being between the at least two electrodes; and a movement component for moving the carbon source in a first direction relative to the container to the inlet opening, the at least two electrodes applying a current in a second direction, the first direction not being the same as the second direction.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments disclosed herein relate to the production of graphene, and in particular to methods and devices for the continuous production of graphene.

[0002] Graphene can be produced by the conversion of a carbon source by Joule heating. The carbon source is a carbon-based powder that is filled into a small quartz tube, and a voltage is applied across the powder material via metal (copper, copper wool, brass) electrodes. However, traditional methods of synthesizing graphene create several challenges for industrial applications, making the method impractical for mass production of graphene.

[0003] Furthermore, quartz tubes that can be used for Joule heating are degraded and contaminated during the Joule heating process when the carbon powder comes into contact with the quartz, making them cost-inefficient. Quartz tubes must be discarded after a single use, which can significantly increase the cost of producing graphene on an industrial scale. Copper wool, used as an electrode, also degrades during this process, further increasing the cost of graphene production. The use of metal electrodes, such as copper and brass, that come into direct contact with the graphene can also add metal contaminants to the resulting graphene powder. Conventional graphene synthesis devices also require assembly and disassembly between batches of graphene, preventing large-scale, continuous graphene production.

[0004] Therefore, there is a need for new cost-effective methods, products, and devices for producing graphene on an industrial scale. Methods, products, and devices for producing graphene that preserve the quartz used during synthesis could reduce costs. Furthermore, there is a need for products, methods, and devices that allow for continuous processing of the materials needed to produce graphene, thereby enabling low-cost industrial production of graphene. Summary of the Invention

[0005] According to some embodiments, there is a device for synthesizing graphene. The device includes a container having a space for holding a carbon source. The container has an inlet opening for receiving the carbon source material. The device includes at least two electrodes for applying a current through the space for Joule heating the carbon source. The space for Joule heating the carbon source is between the at least two electrodes. The device also includes a movement component for moving the carbon source to the opening in a first direction relative to the container, and the at least two electrodes apply a current in a second direction. The first direction is not the same as the second direction.

[0006] The device may also include an exit opening positioned relative to the at least two electrodes to allow movement of the graphene out of the space for Joule heating the carbon source. The entrance opening may be positioned relative to the at least two electrodes to allow movement of the carbon source into the space for Joule heating the carbon source while applying an electric current.

[0007] The device may also include a power source connected to the electrodes for passing an electrical current through the electrodes to convert at least a portion of the carbon source to graphene in the space for Joule heating of the carbon source.

[0008] The device may provide that the at least two electrodes are made from at least one of the group including copper, brass, stainless steel, and graphite.

[0009] The device may provide that at least two electrodes have vents to allow escape of gas when an electric current is applied to the carbon source.

[0010] The device may provide that the space for joule heating the carbon source is surrounded by at least one quartz wall.

[0011] The device may provide that at least one of the at least two electrodes surrounds a space for Joule heating the carbon source.

[0012] The device may provide that at least two of the electrodes are resilient at elevated temperatures.

[0013] The device may provide for at least two electrodes operating at temperatures from room temperature to 3200°C.

[0014] The device may also include a pretreatment electrode for heating the carbon source to a temperature of 400°C to 800°C.

[0015] The device can provide that at least two electrodes are configured to apply an electric current that heats the carbon source to a temperature of between 2800°C and 3200°C.

[0016] The device may also include a carbon source reservoir for holding the carbon source prior to moving the carbon source to the space for Joule heating.

[0017] The device may also include a graphene reservoir for collecting the graphene after the carbon source is moved out of the space for Joule heating.

[0018] The device may also include a compacting component for compacting the carbon source.

[0019] The device may provide that the compression component is a compression piston for compressing the carbon source.

[0020] The device may provide that the compression component is a compression corkscrew.

[0021] The device may provide that the electrode is at least one of the group including a ring electrode, a pin electrode, and a mesh electrode.

[0022] The device may provide for at least two electrodes positioned opposite each other.

[0023] The device may provide for at least two electrodes arranged concentrically with respect to one another.

[0024] The device may provide that the current is DC.

[0025] The device may provide that the current is AC.

[0026] The device may provide a combination of AC and DC current.

[0027] The graphene can be produced by the device.

[0028] The graphene may be turbostratic graphene.

[0029] According to some embodiments, there is a device for synthesizing graphene. The device includes an inner electrode and an outer electrode. The device also includes a space for Joule heating the carbon source, with the carbon source between the inner electrode and the outer electrode. The inner electrode and the outer electrode are positioned to apply a current radially to the space for Joule heating the carbon source. The device also includes an inlet opening positioned relative to the inner electrode and the outer electrode to allow movement of the carbon source into the space for Joule heating the carbon source. The device also includes a power source connected to the inner electrode and the outer electrode to apply a current to the inner electrode and the outer electrode to convert at least a portion of the carbon source in the space for Joule heating the carbon source into graphene.

[0030] The device may provide an outer electrode surrounding a space for Joule heating the carbon source.

[0031] The device may also include a cooling component for cooling at least one of the group comprising the inner electrode and the outer electrode.

[0032] The device may provide that the current is DC.

[0033] The device may provide that the current is AC.

[0034] The device may provide a combination of AC and DC current.

[0035] According to some embodiments, there is a device for synthesizing graphene. The device includes a container for holding a carbon source. The container includes a first electrode. The device also includes a space for Joule heating the carbon source by applying a current between the second electrode and the first electrode. The carbon source is disposed between the first electrode and the second electrode. The device also includes a movement component for moving the container into the space for Joule heating the carbon source. The device also includes a power source connected to the first electrode and the second electrode for applying a current to the electrodes to convert at least a portion of the carbon source into graphene.

[0036] The device may provide that the moving component is a conveyor belt.

[0037] According to some embodiments, there is a method for synthesizing graphene. The method includes moving a carbon source in a first direction to a space for Joule heating the carbon source in the first direction. The method also includes applying a current to the carbon source in a second direction by at least two electrodes positioned to enable movement of the carbon source into the space for Joule heating the carbon source while applying the current. The first direction and the second direction are not the same.

[0038] The method may provide that applying a current to the carbon source includes applying a first current to the carbon source at a lower voltage to remove moisture and volatile materials from the carbon source, and applying a current to the carbon source may also include applying a second current to the carbon source at a higher voltage to convert the carbon source to graphene.

[0039] The method may provide for a lower voltage to heat the carbon source to a temperature of 400°C to 800°C.

[0040] The method may provide that the current is applied for 50 milliseconds to about 1 second.

[0041] The method may provide a higher voltage to heat the carbon source to 2800°C to 3200°C.

[0042] The method may also include compressing the carbon source.

[0043] The method may provide that the carbon source is compressed using a compression piston.

[0044] The method may provide that the carbon source is compressed using a compression corkscrew.

[0045] The method may also include removing unconverted carbon from the graphene.

[0046] The method may provide that the carbon source is moved using a compression piston.

[0047] The method may provide that the carbon source is moved using a conveyor belt.

[0048] The method may provide that at least two electrodes are positioned opposite each other.

[0049] The method may provide that at least two electrodes are arranged concentrically with respect to one another.

[0050] The method may provide that the electrode is at least one of the group including a ring electrode, a pin electrode, and a mesh electrode.

[0051] The method may provide that the movement of the carbon source into the space for Joule heating the carbon source is continuous.

[0052] The method may provide that the movement of the carbon source to the space for joule heating the carbon source is in batches.

[0053] The method may provide that the current is DC.

[0054] The method may provide that the current is AC.

[0055] The method may provide that the current is a combination of AC and DC.

[0056] Graphene can be produced from the method.

[0057] The graphene may be turbostratic graphene.

[0058] According to some embodiments, there is a device for synthesizing graphene. The device includes a container having a space for holding a carbon source, the container having an entrance opening for receiving the carbon source. The device also includes at least two ring electrodes for applying a current through the space for Joule heating the carbon source. The space for Joule heating the carbon source is between the at least two ring electrodes. The device also includes a movement component for moving the carbon source relative to the container to the entrance opening in the same direction as the at least two ring electrodes apply the current.

[0059] The device may also include an exit opening positioned relative to the at least two ring electrodes to allow movement of the graphene out of the space for Joule heating of the carbon source. The entrance opening may be positioned relative to the at least two electrodes while applying a current to allow movement of the carbon source into the space for Joule heating of the carbon source.

[0060] The device may also include a power source connected to the at least two ring electrodes for passing an electric current through the electrodes to convert at least a portion of the carbon source to graphene in the space for Joule heating the carbon source.

[0061] The device may provide that the at least two electrodes are made from at least one of the group including copper, brass, stainless steel, and graphite.

[0062] The device may provide that at least two of the electrodes include vents for allowing gas to escape when an electric current is applied to the carbon source.

[0063] The device may provide that the space for joule heating the carbon source is surrounded by at least one quartz wall.

[0064] The device may provide that the at least two ring electrodes are resilient at elevated temperatures.

[0065] The device may include a pretreatment ring electrode for heating the carbon source to a temperature of 400°C to 800°C.

[0066] The device can provide that at least two electrodes are configured to apply an electric current that heats the carbon source to a temperature of between 2800°C and 3200°C.

[0067] The device may include a carbon source reservoir for holding the carbon source prior to moving the carbon source to a space for Joule heating.

[0068] The device may include a graphene reservoir for collecting graphene after moving the carbon source out of the space for Joule heating.

[0069] The device may provide a moving component to compact the carbon source.

[0070] The device may provide that the moving component is a compression corkscrew.

[0071] The device may include a compacting component for compacting the carbon source.

[0072] According to some embodiments, there is a method for synthesizing graphene. The method includes moving a carbon source in a first direction into a space for Joule heating the carbon source. The method also includes applying a current to the carbon source in a second direction by at least two ring electrodes arranged to enable movement of the carbon source into the space for Joule heating the carbon source. The first direction and the second direction are the same.

[0073] The method may provide that applying a current to the carbon source includes applying a first current to the carbon source at a lower voltage to remove moisture and volatile materials from the carbon source. The method may also include applying a second current to the carbon source at a higher voltage to convert the carbon source to graphene.

[0074] The method may provide for a lower voltage to heat the carbon source to a temperature of 400°C to 800°C.

[0075] The method may provide that the current is applied for 50 milliseconds to about 1 second.

[0076] The method may provide a higher voltage to heat the carbon source to 2800°C to 3200°C.

[0077] The method may also include compressing the carbon source.

[0078] The method may provide that the carbon source is compressed using a compression piston.

[0079] The method may provide that the carbon source is compressed using a compression corkscrew.

[0080] The method may also include removing unconverted carbon from the graphene.

[0081] The method may provide that the carbon source is moved using a compression piston.

[0082] The method may provide that the carbon source is moved using a conveyor belt.

[0083] The method may provide that at least two electrodes are positioned opposite each other.

[0084] The method may provide that the movement of the carbon source into the space for Joule heating the carbon source is continuous.

[0085] The method may provide that the movement of the carbon source to the space for joule heating the carbon source is in batches.

[0086] The method may provide that the current is DC.

[0087] The method may provide that the current is AC.

[0088] The method may provide that the current is a combination of AC and DC.

[0089] Graphene can be produced from the method.

[0090] The graphene may be turbostratic graphene.

[0091] Other aspects and features will become apparent to those of ordinary skill in the art upon review of the following description of several exemplary embodiments. [Brief explanation of the drawings]

[0092] The drawings included herein are intended to illustrate various examples of the articles, methods, and corkscrew devices herein.

[0093] [Figure 1] FIG. 1 illustrates a diagram of a device for producing graphene in a laboratory environment, according to one embodiment. [Figure 2] FIG. 1 illustrates a diagram showing the compression direction and electrodes of a device for producing graphene in a laboratory environment, according to one embodiment. [Figure 3] FIG. 1 illustrates a diagram showing the compression direction and electrodes of a device with graphite disks for producing graphene in a laboratory environment, according to one embodiment. [Figure 4] FIG. 1 illustrates a diagram of a device for continuous and batch synthesis of graphene, according to one embodiment. [Figure 5] FIG. 1 illustrates a diagram of a device for continuous and batch graphene synthesis utilizing piston-like action, according to one embodiment. [Figure 6] 1 illustrates a side view and a top view of a device for continuous and batch graphene synthesis utilizing a vessel and electrodes from the top and bottom of the vessel, according to one embodiment. [Figure 7] FIG. 1 illustrates a diagram of a device for continuous and batch synthesis of graphene utilizing a belt for graphene production by Joule heating, according to one embodiment. [Figure 8] FIG. 1 illustrates a side view of a device for continuous and batch synthesis of graphene utilizing corkscrew compression with split ring electrodes adjacent to spaces for Joule heating of a carbon source, according to one embodiment. [Figure 9] FIG. 1 illustrates a diagram of a device for continuous and batch graphene synthesis utilizing corkscrew compression with mesh and ring electrodes adjacent to a space for Joule heating of a carbon source, according to one embodiment. [Figure 10] 1 illustrates a device for continuous and batch synthesis of graphene utilizing ring-shaped electrodes adjacent to a space for Joule heating of a carbon source, according to one embodiment. [Figure 11A] FIG. 1 is a cross-sectional view of a device for continuous and batch synthesis of graphene utilizing a radial electrode array, according to one embodiment. [Figure 11B] FIG. 1 shows a cross-sectional view of a device for continuous and batch synthesis of graphene utilizing a radial electrode array, according to one embodiment, and a cross-sectional view of an extrusion screw that introduces and removes a carbon source into the radial space of the device. [Figure 12] 1 illustrates a flowchart of a method for synthesizing graphene, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0094] Various devices or processes are described below to provide examples of each claimed embodiment. The embodiments described below do not limit the claimed embodiments, which may cover processes or devices different from those described below. The claimed embodiments are not limited to devices or processes having all the features of any one device or process described below, or to features common to multiple or all of the devices described below.

[0095] Provided herein are devices and methods for the continuous synthesis of graphene from a carbon source by Joule heating.

[0096] The term "graphene" refers to the sp -s ... 2 It refers to a material that is a one-atom-thick planar sheet of bonded carbon atoms, further containing an intact ring structure of carbon atoms and aromatic bonds over at least the majority of the inter-sheet, and lacking significant oxidative modification of the carbon atoms. Graphene can be distinguished from graphene oxide in that it contains a low level of oxygen-containing groups such as OH, COOH, and epoxides. The term "graphene monolayer" refers to graphene that is a single layer of graphene. The term "very few-layer graphene" refers to graphene that is one to three layers of graphene. The term "few-layer graphene" refers to graphene that is two to five layers of graphene. The term "multilayer graphene" refers to graphene that is two to ten layers of graphene.

[0097] The term "turbostratic graphene" refers to graphene with little order between the graphene layers. Other terms that may be used include misoriented, misaligned, twisted, rotationally faulted, and weakly coupled. The rotational stacking of turbostratic graphene helps relax interlayer bonds and increase interplane spacing, resulting in superior physical properties compared to competing graphene structures when compared on a similar weight basis. Subtle differences in the stacking orientation of adjacent layers translate into significant differences in product performance attributes. An important performance benefit evident in turbostratic graphene is that the multilayer graphene structure is more likely to separate into a smaller number of individual graphene layers, and the graphene layers tend not to recombine. The turbostratic nature of graphene can be observed and confirmed by Raman spectroscopy, transmission electron microscopy (TEM), selected area electron microscopy (SAED), scanning transmission electron microscopy (STEM), and X-ray diffraction (XRD) analysis.

[0098] The term "opening" generally refers to any passageway through which a carbon source or graphene can pass into or out of the space for Joule heating the carbon source of a device for synthesizing graphene. An opening can include an unobstructed entrance or exit. For example, an "entrance opening" can be any entry point for moving a carbon source or graphene into the space for Joule heating the carbon source of a device for synthesizing graphene. An "exit opening" can be any exit point used to move a carbon source or graphene out of the space for Joule heating the carbon source of a device for synthesizing graphene.

[0099] The term "carbon source" generally refers to any carbon-based material that can be converted into graphene material, preferably turbostratic graphene. The carbon source can be in any form, including powder or compressed pill form. Carbon sources include, but are not limited to, petroleum coke, tire carbon black, carbon black, metallurgical coke, plastic ash, plastic powder, ground coffee, anthracite, coal, cornstarch, pine bark, polyethylene microwax, wax, Chemplex 690, cellulose, naphthenic oil, asphaltenes, Gilsonite, and carbon nanotubes.

[0100] In some embodiments, the apparatus, methods, and articles of manufacture provided herein can provide continuous synthesis of graphene, where a carbon source is transferred into a space for Joule heating, converted to graphene, and simultaneously transferred out continuously. In some embodiments, Joule heating can be performed in batches, where a first batch of carbon source is transferred into the Joule heating space, the carbon source is converted to graphene, the carbon source is transferred out of the Joule heating space, a new batch of carbon source is transferred into the Joule heating space, and the process is repeated. Joule heating in batches can be partial or full batches. In some embodiments, multiple partial batches can be transferred into the Joule heating space before all of the batches are transferred out. Similarly, multiple partial batches can be transferred out of the Joule heating space before another batch is transferred in.

[0101] The flash joule heating synthesis method and compositions thereof are described in Patent Cooperation Treaty Application having International Publication No. WO 2020 / 051000A1 by Tour et al., having an international publication date of March 12, 2020, which is incorporated herein by reference.

[0102] Methods for synthesizing graphene by Joule heating of carbon pills and compositions thereof are described in Patent Cooperation Treaty application having International Application No. PCT / CA2020 / 051368 by Mancevski, filed October 13, 2020, which is incorporated herein by reference.

[0103] Referring to FIG. 1, a diagram of a device for producing graphene in a laboratory setting is illustrated, according to one embodiment. The graphene synthesis device 100 consists of a mechanical assembly including a container 115 (e.g., a quartz tube), a carbon source 105, and an electrode 110, which may be made of copper wool or graphite. The mechanical assembly also includes a compression piston / screw and a protective enclosure, not shown in FIG. 1. The device also includes an electrical assembly for supplying current to the electrode. The electrical assembly includes a power supply, a capacitor bank, a high-power switch, and a controller, not shown in FIG. 1. The electrode 110 is in direct contact with the carbon source 105. The carbon source 105 also contacts the wall of the quartz tube 115, which causes degradation of the quartz tube 115 after the Joule heating process. The Joule heating current is 800-2500 amperes. Because they are in direct contact with the carbon source and the electrode 110, if the electrode 110 is made of brass or copper, they may partially melt during the Joule heating process and introduce impurities into the graphene.

[0104] The device 100 in Figure 1 can produce 1 g of graphene per 15 minutes or a batch of 30 g of graphene per day from various carbon sources. The quartz tube 115 has an inner diameter (ID) of 15 mm and a carbon volume of approximately 5 cc. The Joule heating process consists of loading carbon powder into the quartz tube 115. The process also includes plugging each end of the quartz tube 115 with a layer of electrodes 110. The process also includes compressing the carbon source with a screw. Joule heating is performed for 10 ms to 100 ms, and the resulting graphene is removed from the tube. In a laboratory setting, this process is performed manually and takes approximately 15 minutes per batch. While most of the processing time is overhead, the actual carbon-to-graphene processing time is only 10 ms to 150 ms. The energy required to convert carbon to graphene is 4 Wh / g (14.4 kJ / g) to fully discharge the Joule heating process in 100 ms. Due to the speed limitations of high power electronics, some of the energy is wasted.

[0105] Referring to FIG. 2, a diagram illustrating the orientation of the compression and electrodes of a device for producing graphene in a laboratory setting is illustrated, according to one embodiment. The orientation of the electrodes 210 and the compression direction are primarily aligned. Both ends of the carbon source 205 are compressed by the electrodes 210. The advantages of the design shown in FIG. 2 include the possibility of using a standard round quartz tube 215; light emitted during Joule heating of the carbon source 205 (via a radiative cooling process) can exit through the quartz tube 215, shortening the cooling time; and gas exits through the copper wool 210. The device 200 results in little loss of graphene material during handling. The device 200 also has drawbacks, such as requiring disassembly to remove the graphene. Furthermore, graphene sticks to the copper, and copper wool particles end up mixed with the graphene. Furthermore, the quartz tube 215 becomes contaminated with each use.

[0106] Referring to FIG. 3, a diagram illustrating the compression and electrode orientation of a device with a graphite disk for producing graphene in a laboratory setting is illustrated, according to one embodiment. To overcome the shortcomings of the device 200 of FIG. 2, a porous graphite plug or disk 220 is placed as an electrode component that directly contacts the carbon source 305. Optionally, a separate plug made of copper wool 310 can be added to each side of the graphite 320, the side of the graphite not in contact with the carbon source. The copper wool 310 can then be contacted by a copper or brass rod connected to a DC or AC power source, such as a battery or capacitor. The carbon source 305 is compressed from one side in the same plane as the electrode orientation. In some embodiments, compression can be performed from both sides in the same plane as the electrode orientation.

[0107] The advantage of device 300 is the possibility of using a standard round quartz tube 315. Light emitted during Joule heating of the carbon source 305 (radiative cooling) exits through the quartz tube 315, shortening the cooling time. Gases can exit through the porous graphite and copper wool. Furthermore, if the graphite is not porous, process gases can exit through the gap between the graphite plug and the inner diameter of the quartz tube. Furthermore, using device 300 reduces material loss during handling. Furthermore, graphene synthesized after carbon source 305 is exposed to high temperatures of 2800°C to 3200°C. It does not adhere to the graphite plug, or if the synthesized graphene adheres, it can be easily removed from the graphite 320.

[0108] In some embodiments, the methods, devices, and products increase batch sizes from 1 g to 10 g. Increasing batch size directly scales the manufacturing process. Existing laboratory setups use quartz tubes with an ID of 15 mm and a tube length of approximately 25 mm, with a carbon mass of 1 g per batch and a volume of approximately 5 cc per batch. Due to the resistive Joule heating of the charge, doubling the tube diameter requires a four-fold increase in current with the same voltage requirements. Doubling the tube length requires a two-fold increase in voltage with the same current requirements. Therefore, batch size may be limited by available switch electronics. Typical insulated gate bipolar transistor (IGBT) high-power switching modules commonly used in power components, uninterruptible power supply (UPS) systems, and solar inverters have voltages up to 1700 V and currents up to 1800 A, allowing for flexible reactor tube design. Multiple IGBT switches operating in parallel may be used to enable currents up to 5000 A or more. This means that it is not practical to design batches larger than 10 g. Scaling can be achieved by increasing the frequency (turnaround time) of each batch.

[0109] In some embodiments, the methods, devices, and products provided herein achieve batch sizes of 5 g per batch (volume of approximately 24 cc / batch), which corresponds to 1 kg / day of production. This can be achieved with a quartz tube with an ID of 20 mm and a tube length of approximately 75 mm. The conversion power for 5 g is approximately 110 kW / g (1500 A and 750 V). Because power is provided by a bank of capacitors with linear voltage discharge, the average voltage used in the energy calculation is ½ of the maximum voltage. In some embodiments, batch sizes of 10 g per batch (volume of approximately 48 cc / batch) can be possible, which allows for commercial production with the addition of automated and parallel manufacturing lines capable of producing 1 ton / hour (8 tons / day). 10 g per batch can be achieved with a quartz tube with an ID of 20 mm and a tube length of approximately 150 mm. The conversion power for 10 g is approximately 110 kW / g (1500 A and 1500 V).

[0110] Referring to Table 1, a summary of the device parameters for three different embodiments is provided, each enabling larger scale manufacturing. Embodiment 1 enables the smallest scale manufacturing of graphene. Embodiment 2 enables larger scale manufacturing than Embodiment 1. Embodiment 3 enables the largest scale manufacturing of the three embodiments, enabling commercial scale manufacturing. [Table 1]

[0111] In some embodiments, the methods, devices, and products provided herein reduce the process time (turnaround time) of each batch process for graphene synthesis. This reduction in process time directly correlates to improved scalability of graphene production. With the devices of Figures 1, 2, and 3, the graphene synthesis process takes 15 minutes per 1-g batch. While most of the processing time is overhead, the actual carbon-to-graphene processing time is only 10 ms to 150 ms. The remaining time is spent manually loading the carbon, manually compressing the carbon powder, and manually removing the graphene. Using the devices of Figures 1, 2, and 3, 30 batches of 1-g carbon source can produce 30 g of graphene per day.

[0112] Producing 1 kg of graphene per day can be achieved with 200 batches of 5 g each. Assuming an 8-hour production day, producing 200 batches requires a 2-minute allocation per batch. With a 2-minute throughput, the graphene synthesis process can be operated in semi-batch mode, where 10 or more batches are loaded simultaneously and each 5 g of carbon undergoes the Joule heating process one after the other, without the need for loading and unloading.

[0113] Similarly, production of 1 ton / hour can be achieved at 100,000 batches per hour, each 10g. Implementing 40 parallel production lines means each line needs to produce 20,000 batches per day, or 2500 batches of 10g each per hour, assuming an 8-hour production day. Producing 2500 batches per hour requires a 1.4-second allocation per batch. Demand clearly calls for a level of automation where carbon is fed into and removed from the process tube in a continuous fashion, with 10g of carbon heated for 1.4 seconds each, without the need for loading and unloading. Alternatively, using 100 parallel production lines is another reasonable possibility, increasing the allocation to 3.6 seconds.

[0114] See Table 2, which is a summary of the manufacturing parameters for the three embodiments of Table 1. [Table 2]

[0115] In some embodiments, the methods, devices, and articles enable a continuous process for graphene production. Continuous graphene synthesis methods have the ability to continuously load and unload carbon powder. Continuous graphene synthesis methods also have the ability to compress the carbon powder independent of loading and unloading. Continuous graphene synthesis methods also have electrode orientation that is independent of the direction of carbon source flow. Continuous graphene synthesis methods also have the availability of vent holes / vent apertures to allow for the rapid evacuation of hot gases created as a result of the Joule heating process. Additionally, the reactor needs to be vented during the Joule heating process to prevent thermal and electrodynamic forces from compressing the carbon source.

[0116] Referring to FIG. 4, a device for continuous graphene synthesis is illustrated, according to one embodiment. Device 400 enables scalable production of graphene. Electrode 410 is perpendicular to the direction of compression of carbon source 405 by piston 415. When carbon source 405 is forced into the space for Joule heating carbon source 420 in the middle of electrode 410, the carbon source can be Joule heated to form graphene 425. When new carbon powder is forced into inlet opening 422 of container 421 and forced into the space for Joule heating carbon source 420, the resulting graphene 425 produced from the Joule heating of carbon source 405 can be ejected on the opposite side from where the new carbon source 405 is inserted. In some embodiments, there is no piston or other object on the exit side of the tube, as friction between the carbon and the tube serves to stop the flow of carbon and allow Joule heating to begin.

[0117] An advantage of the device 400 of Figure 4 is that the device allows for a continuous flow of carbon source 405 and graphene 425. The device 400 also does not need to be disassembled to insert the carbon source 405 or to remove the graphene 425. Furthermore, the graphene does not stick to the graphite electrode 410. There is little loss of graphene material during processing.

[0118] In some embodiments, the device for continuous graphene synthesis includes a second set of electrodes for independent pretreatment of the carbon source. A secondary electrode set, located to the left of the primary electrode set 410, is used to pretreat the carbon at lower temperatures, between 400°C and 1000°C, to carbonize the carbon source and remove moisture, volatiles, and other substances that evaporate at these temperatures. After the carbon source is pretreated, the carbon source 405 is forced toward the primary electrode 410, where it is Joule heated and converted to graphene. The process tube can be any size, including, but not limited to, circular or rectangular. It can be made from, but not limited to, quartz or ceramic. The force required to move large segments of graphene must be large enough to move the carbon source.

[0119] Referring to FIG. 5 , a diagram of a device for continuous graphene synthesis utilizing a piston-like action is illustrated, according to one embodiment. The device 500 enables scalable production of graphene. The device 500 includes a moving component 525 for moving a carbon source 505 into an entrance opening 515 of a container 516. The moving component also compresses the carbon source 505 and pushes the carbon source 505 toward a space for Joule heating the carbon source 520. The device 500 also includes a carbon source reservoir 535 for holding the carbon source 505 before it moves to the entrance opening 515. The current is not in the same direction as the compression of the carbon source 505. The current is preferably perpendicular or nearly perpendicular to the flow of the carbon source 505, but can be in any direction other than the direction of compression. The flow of carbon 505 can be continuous, and the electrode 510 does not impede the flow of the carbon source 505. After the carbon source 505 is Joule heated, the carbon source 505 is converted into graphene powder 506 which follows the flow path of the carbon source 505. The converted graphene 506 travels through an exit opening 545 to a graphene reservoir 540. Alternatively, the pistons 525 and 530 can be replaced with a corkscrew or extrusion screw that rotates continuously instead of moving in a back and forth stroke.

[0120] The device 500 in Figure 5 can be constructed from a quartz or ceramic tube (approximately 150 x 150 mm) of oval or rectangular cross section, with a cutout in the center section for parallel plate electrodes (approximately 150 x 18 mm). Alternatively, the electrodes can be curved to match the radius of curvature of the inlet and outlet conduits. The volume between the electrodes needs to accommodate 24 cc (5 g) or 48 cc (10 g), according to the dimensions in Table 1. Unlike the device for producing graphene in a laboratory setting in Figure 3, the functions of the compression pistons 525, 530 and electrode 510 in Figure 5 are performed by separate components. The electrode 510 can be made from, but is not limited to, copper, stainless steel, graphite, or tungsten. The electrode 510 is attached to the quartz but has a vent hole to allow hot process gases to escape during the Joule heating process. The compression pistons 525, 530 can be made from a dielectric material, such as quartz or ceramic, to prevent shorting the pistons to ground. The carbon source 505 is fed through a carbon source reservoir 535 into the inlet opening 515 of the process tube. The movement of the carbon source is assisted by a shaker while the first compression piston is retracted to the left. After the carbon powder is distributed into the tube, the first compression piston 525 moves a stroke sufficient to transfer the converted carbon 506 from the space below the electrode for Joule heating. At the same time, the second compression piston retracts to the right, allowing the graphene to be removed into a collection bottle. The movement is assisted by a shaker or vacuum suction. After the stroke is completed, the second compression piston 530 pushes in to block the tube, and the first compression piston 525 applies a predetermined pressure to the carbon source 505 until the Joule heating process is complete. The piston cycle must match the throughput of the continuous process. The flow of the carbon source 505 and graphene material 506 is in a sealed environment, making the operation safe.

[0121] 6, there is shown a side view and a top view of a device for continuous graphene synthesis utilizing a vessel and electrodes viewed from the top and bottom of vessel 620, according to one embodiment. Device 600 enables scalable production of graphene. In this embodiment, vessel 620 is not a tube. Instead, carbon source 605 is loaded into vessel 620 through an inlet opening, and electrodes 610 reside at the top and bottom of vessel 620.

[0122] Advantages of the device in FIG. 6 include that the device 600 allows for a continuous carbon source 605 / graphene 606 flow. The device 600 does not need to be disassembled to insert the carbon source 605 or remove the graphene 606. The graphene 606 does not adhere to the graphite electrodes 610, and the device 600 allows for the use of a second set of electrodes 610 for independent pretreatment of the carbon source 605. A secondary electrode set located to the left of the primary electrode set 610 is used to pretreat the carbon source at a lower temperature, between 400°C and 1000°C, to carbonize the carbon source 605 and remove moisture, volatiles, and other substances that evaporate in the pretreatment temperature range. After the carbon source 605 is pretreated, the carbon source container 620 is moved below the primary electrode 610, and the carbon source 605 is converted to graphene 606.

[0123] Referring to FIG. 7, a diagram of a device for continuous graphene synthesis using a belt for graphene production by Joule heating is illustrated, according to one embodiment. Device 700 enables scalable production of graphene. Carbon source 705 is supplied via reservoir 725 to inlet opening 731 of quartz or ceramic vessel 730, which is electrically grounded and has a metal bottom electrode 711 that is part of a continuous belt 735. Quartz vessel 730 can be a cylinder with a diameter of 20 mm and a depth of 150 mm, with a pitch of 50 mm between boats. Piston / electrode 710 is a cylinder with a diameter >20 mm to cover and seal the top of the boat. Piston / electrode 710 can be copper, steel, tungsten, or graphite. A vent hole is included in electrode 710. The volume of vessel 730 is 24 cc (5 g) or 48 cc (10 g), according to the dimensions from Table 1. The container 730 is moved into the joule heating space 720 in a direction different from the direction in which the current is applied by the electrodes 710,711.

[0124] The carbon source 705 is dispensed slowly until the container 730 reaches the space under the piston / electrode 710, where it is compressed and Joule heating is applied to the carbon source 705, converting it to graphene 706. Once the belt leaves the space for Joule heating the carbon source 720, the container 730 is emptied into a collection bottle (not shown). The piston cycle is 2 minutes or 1.4 seconds, matching the throughput of continuous graphene synthesis. The belt speed moves the next container under the electrode every 2 minutes or 1.4 seconds (depending on the desired scale). The entire device is sealed for safe operation. The limiting step in the device of Figures 6 and 7 is the rate at which the container 730 is filled with carbon source 705 from reservoir 725.

[0125] Referring to FIG. 8 , a side view of a device for continuous graphene synthesis using a corkscrew or extrusion screw compressor with split ring electrodes adjacent to a space for Joule heating of a carbon source is illustrated, according to one embodiment. The device 800 enables scalable production of graphene 806. The carbon source 805 is moved into an inlet opening 830 of a vessel 831, which is an extrusion component, and compressed by a corkscrew compressor 815. The corkscrew compressor 815 pushes the carbon source 805 past two sets of electrodes 810, 811, located on the side of a flow tube where a pretreatment space 821 and a space for Joule heating of the carbon source 820 are located. The electrodes are positioned perpendicular to the flow of the carbon source. The corkscrew 815 can be a single-corkscrew or twin-corkscrew mechanism. The electrodes 810, 811 are parallel plates 830 or opposing half-side electrodes 830 located opposite each other at the same level of the extrusion component. A first set of electrodes 811 is used to pre-flush the carbon source 805, and another set 810 is used to Joule heat the carbon source 805. The pre-treated carbon source is moved toward a space for Joule heating the carbon source 820, where a second set of electrodes 810 is located. An optional spring-loaded lid 825 can hold the graphene powder 806 until it is ready to be removed. The opening of the lid 825 is synchronized with the movement of the corkscrew 815. The current is perpendicular to the flow of the carbon source 805.

[0126] Alternate sets of electrodes 812, 813 can be used in the device 800 of FIG. 8. Ring electrodes 813 can be used for one or more terminals, and pin electrodes 812 can be used for at least one terminal. The cross section shows that the pretreatment electrodes 811 in the pretreatment space 821 are parallel opposing electrodes 830, and the Joule heating electrodes 812, 813 are the ring electrode 813 for the negative terminal and the pin electrode 812 for the positive terminal. The ring 813 and pin 812 electrodes are concentric, providing Joule heating of the carbon source 805 in the space between the pin and ring for Joule heating of the carbon source 820.

[0127] Referring to FIG. 9 , a diagram of a device for continuous graphene synthesis using corkscrew compression with mesh and ring electrodes adjacent to a space for Joule heating of a carbon source is illustrated, according to one embodiment. The device 900 enables scalable production of graphene 906. The carbon source 905 is inserted into a corkscrew mechanism 915 of an extruder-like machine that compresses the carbon source 905 and pushes it past two sets of electrodes 911, 910, positioned upstream and downstream of the carbon flow. The first set of electrodes 911 are mesh electrodes that allow material flow but can be energized to enable Joule heating. The top mesh 930 is a ground electrode, and the bottom electrode 931 is a positive electrode. The electrodes 930, 931 can also be positioned in an opposing orientation, with the positive electrode 931 being the top mesh and the ground electrode 930 being the bottom electrode. The first set of electrodes 911 is for pre-treating the carbon source 905 in a pre-treatment space 921. A second set of electrodes 910 is for Joule heating the carbon source 905 in a space for Joule heating the carbon source 920. An optional spring-loaded lid 925 can hold the graphene powder 906 until it is ready to be removed. The opening of the lid 925 is synchronized with the movement of the corkscrew 915. The current is perpendicular to the flow of the carbon source 905. The carbon source 905 is moved into an inlet opening 922 of a vessel 923, which is an extrusion component.

[0128] In another embodiment shown in Figure 9, the electrodes 911, 912, 913, and 914 are ring electrodes, the ground electrode 913 is the top electrode, and the bottom electrode 912 is the positive terminal. The electrodes 911, 912, 913, and 914 can also be arranged in an opposing orientation. The ring electrodes 911, 912, 913, and 914 can be half-ring, half-pole ring, or quadrature-pole electrodes for more uniform distribution of current through the sample. An optional spring-loaded lid 925 can hold the graphene powder 906 until it is ready to be removed. The opening of the lid 925 must be synchronized with the movement of the corkscrew 915.

[0129] In both examples shown in FIG. 9, the carbon source 905 flows from the top of the tube to the bottom of the tube, and the current flows in the direction of the carbon flow but has an open flow design so as not to impede the carbon powder flow.

[0130] Referring to FIG. 10 , there is illustrated a device for continuous graphene synthesis utilizing ring-shaped electrodes adjacent to a space for Joule heating of a carbon source, according to one embodiment. The device 1000 enables scalable production of graphene 1006. The carbon source 1005 is moved using an extruder-like machine, and the electrodes 1025, 1030 are ring electrodes positioned along the length of the compressed carbon source 1005 stream. One ring electrode 1030 is located immediately adjacent to the extruder's exit opening 1035, and the other electrode 1025 is positioned further along the tube 1040 upstream of the carbon source 1005 stream adjacent to the entrance opening. In this embodiment, the tube 1040 is a vessel, and the carbon source is moved into the tube's entrance opening 1026 in the same direction as the current from the ring electrodes 1025, 1030. The separation of the rings 1025, 1030 determines the size of the space for Joule heating of the carbon source 1045. Current flows from the inner ring of the first electrode 1025 to the inner ring of the second electrode 1030. During operation, the space for Joule heating the carbon source 1045 between the electrodes is filled with the carbon source 1005, and Joule heating of the carbon source 1005 is performed. The synthesized graphene 1006 in the space for Joule heating the carbon source 1040 between the electrodes is removed through the outlet opening 1035. A restrictive orifice 1050 is added to the outlet opening 1035 to prevent undesired flow of the graphene powder 1006. Furthermore, friction of the graphene powder 1006 in the tube 1040 prevents undesired flow of the graphene powder 1006. The flow of the carbon source 1005 can be a complete batch, and the space for Joule heating the carbon source between the electrodes 1045 is completely filled. The flow of carbon source 1005 can also be semi-batch, where only a portion of graphene 1006 is removed and the same portion of carbon source 1005 is backfilled. The flow of carbon source 1005 can also be continuous, where the discharge is periodic with respect to the continuous movement of carbon source 1005 and graphene 1006.

[0131] Referring to FIG. 11A, a cross-sectional perspective view of a device for continuous graphene synthesis utilizing a radial electrode array is illustrated, according to one embodiment. The device includes an inner electrode 1110 and an outer electrode 1120, preferably made of graphite. The device's electrical potential is radial, starting from the outer surface of the inner electrode 1110 and ending on the inner surface of the outer electrode 1120, or vice versa. The device 1100 includes an outer graphite electrode 1120, which functions as both an electrode and a confinement tube to replace the quartz tube, and can be cooled externally using conduction or convection cooling. The device can include a copper tube 1105 with a circulating coolant made from dielectric oil or a similar dielectric liquid, and a heat exchanger (not shown), where the copper pipe 1105 is inserted inside the hollow inner electrode 1110 to cool the inner electrode 1110 and remove heat from the carbon source 1130. The device 1100 also includes an upper spring 1115 for pushing the upper quartz lid 1125 and compressing the carbon source 1130 in the space 1131, and a bottom spring 1140 for pushing the bottom quartz lid 1135 and compressing the carbon source 1130 in the space 1131. The carbon source 1130 is moved into the space for Joule heating and conversion of the carbon source 1131 to graphene. The carbon source 1130 can be inserted and removed in a batch mode, where the carbon source 1130 is inserted into the radial space 1131, Joule heated, converted to graphene, and removed from the radial space 1131. The carbon source 1130 can also be inserted and removed using an extrusion screw that replaces the confinement provided by the quartz lid.

[0132] Current flows radially from the inner electrode 1110 to the outer electrode 1120 or vice versa, and the carbon source 1130 is confined and Joule heated by the outer graphite electrodes 1110 and 1120. In some embodiments, the inner electrode 1110 and outer electrode 1120 may be liquid cooled.

[0133] Because graphite is a blackbody heat acceptor, radiative cooling can occur efficiently from the carbon source 1130 to the outer graphite electrode 1120. The outer graphite electrode 1120 also heats by conduction from the carbon source 1130 but can then re-radiate heat from its outer surface and be further cooled by convection or conduction from the outside. The outer electrode 1120 can be porous graphite, allowing gas and heat to leave the carbon source more efficiently. The outer electrode 1120 can also have pores along its surface to allow gas to escape from the electrode's interior to the exterior. Because the graphite electrode confines the carbon source and converted graphene, a consumable quartz tube is not required. The graphite electrodes 1120, 1110 can be used almost indefinitely with minimal wear.

[0134] 11B, there is illustrated a cross-sectional view of a device 1101 for continuous graphene synthesis utilizing a radial electrode array and an extrusion screw 1145 that moves a carbon source 1150 into and out of the radial space of the device 1101, according to one embodiment. The device 1101 includes radially aligned inner 1155 and outer 1160 electrodes. The device 1101 also includes an extrusion screw 1145 that moves carbon source powder 1150 from an outer reservoir (not shown) into a ceramic tube conduit 1170 and then into the radial space between the radial electrodes 1155, 1160. The tube 1170 is a vessel, and the carbon source 1150 is moved into an inlet opening 1171 of the vessel. The extrusion screw 1145 has a hollow shaft 1180. The inner electrode 1155 can be fixed to the shaft of the extrusion screw 1145, and an electrical connection can run through the hollow shaft. The positive terminal 1172 and the negative terminal 1173 are connected to a power source for operation with either alternating current (AC), direct current (DC), or a combination of AC and DC. During operation, the space 1175 for Joule heating the carbon source 1150 between the electrodes 1155, 1160 is filled with the carbon source 1150, and Joule heating of the carbon source 1150 is performed. The synthesized graphene 1165 in the space for Joule heating the carbon source 1150 between the electrodes 1155, 1160 is removed through an exit opening. The movement of the carbon source 1150 is continuous and unimpeded by the electrodes 1155, 1160. Furthermore, the flow of the carbon source 1150 flows longitudinally through the tube, and the current flows radially.

[0135] Referring to Figure 12, there is a flowchart for a method for synthesizing graphene, according to one embodiment. Method 1200 includes, at 1205, moving a carbon source in a first direction into a space for Joule heating the carbon source. Method 1200 optionally includes compressing the carbon source at 1206. Method 1200 also includes, at 1210, applying a current to the carbon source in a second direction with at least two electrodes positioned to enable movement of the carbon source into the space for Joule heating the carbon source to convert at least a portion of the carbon source to graphene. Method 1200 at 1210 may optionally include an additional step at 1215 including applying a first current to the carbon source at a lower voltage to remove moisture and volatiles from the carbon source. The lower voltage generates a lower process temperature that removes moisture and volatiles from the carbon source but does not convert the carbon source to graphene. Method 1200 at 1210 may optionally include an additional step at 1220 including applying a second current at a higher voltage to convert at least a portion of the carbon source to graphene. The higher voltage allows for Joule heating of the carbon source and conversion to graphene. Method 1200 may optionally include removing unconverted carbon from the graphene at 1230.

[0136] Although the above description provides examples of one or more devices, methods, or systems, it will be understood that other devices, methods, or systems may be within the scope of the claims as interpreted by one of ordinary skill in the art.

Claims

1. 1. A device for the synthesis of graphene, comprising: a container having a space for holding a carbon source, the container having an inlet opening for receiving the carbon source; at least two electrodes for applying a current through the space for Joule heating the carbon source, the space for Joule heating the carbon source being between the at least two electrodes, and the at least two electrodes being arranged to apply a current radially to the space for Joule heating the carbon source; a moving component for moving the carbon source in a first direction relative to the container to an inlet opening, wherein the at least two electrodes apply the current in a second direction, and the first direction is not the same as the second direction.

2. 10. The device of claim 1, further comprising an exit opening positioned relative to the at least two electrodes to allow movement of the graphene out of the space for Joule heating the carbon source, and wherein the entrance opening is positioned relative to the at least two electrodes to allow movement of the carbon source into the space for Joule heating the carbon source while applying the current.

3. 10. The device of claim 1, further comprising a power source connected to the electrodes for passing the current through the electrodes to convert at least a portion of the carbon source to graphene in the space for Joule heating the carbon source.

4. 10. The device of claim 1, wherein the at least two electrodes include vents for allowing gas to escape when the electrical current is applied to the carbon source.

5. The device of claim 1 , wherein the space for Joule heating the carbon source is surrounded by at least one quartz wall.

6. 10. The device of claim 1, further comprising: a carbon source reservoir for holding the carbon source before moving the carbon source into the space for Joule heating; and a graphene reservoir for collecting the graphene after moving the carbon source out of the space for Joule heating.

7. The device of claim 1 , further comprising a compacting component for compacting the carbon source.

8. The device of claim 7 , wherein the compression component is a compression piston for compressing the carbon source.

9. The device of claim 1 , wherein the at least two electrodes are positioned opposite each other.

10. The device of claim 1 , wherein the graphene is turbostratic graphene.

11. 1. A device for synthesizing graphene, comprising: an inner electrode and an outer electrode; a space for a carbon source between the inner electrode and the outer electrode for Joule heating the carbon source, the inner electrode and the outer electrode being arranged to apply a current radially to the space for Joule heating the carbon source; an inlet opening positioned relative to the inner electrode and the outer electrode to allow movement of the carbon source into the space for Joule heating of the carbon source; a power source connected to the inner electrode and the outer electrode for passing the current through the inner electrode and the outer electrode to convert at least a portion of the carbon source into graphene in the space for Joule heating the carbon source.

12. The device of claim 11 , wherein the outer electrode surrounds the space for Joule heating the carbon source.

13. to cool at least one of the group including the inner electrode and the outer electrode, The device of claim 11 further comprising a cooling component.

14. 1. A device for synthesizing graphene, comprising: a container having a space for holding a carbon source, the container having an inlet opening for receiving the carbon source; at least two ring electrodes for applying a current through the space for Joule heating the carbon source, the space for Joule heating the carbon source being between the at least two ring electrodes; a moving component for moving the carbon source relative to the vessel toward the inlet opening in the same direction as the at least two ring electrodes apply the current.

15. 15. The device of claim 14, further comprising an exit opening positioned relative to the at least two ring electrodes to allow movement of the graphene out of the space for Joule heating the carbon source, and wherein the entrance opening is positioned relative to the at least two ring electrodes to allow movement of the carbon source into the space for Joule heating the carbon source while applying the current.

16. 15. The device of claim 14, further comprising a power source connected to the at least two ring electrodes for passing the current through the electrodes to convert at least a portion of the carbon source to graphene in the space for Joule heating the carbon source.

17. 15. The device of claim 14, further comprising a pretreatment ring electrode for heating the carbon source to a temperature of 400°C to 800°C.

18. 15. The device of claim 14, wherein the at least two ring electrodes are configured to apply the current that heats the carbon source to a temperature of between 2800°C and 3200°C.

19. 15. The device of claim 14, further comprising: a carbon source reservoir for holding the carbon source before moving the carbon source into the space for Joule heating; and a graphene reservoir for collecting the graphene after moving the carbon source out of the space for Joule heating.

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