Apparatus, method and carbon pellet for synthesizing graphene

Abstract

An apparatus for converting carbon pills to graphene is provided, comprising a space between at least two conductive surfaces, the conductive surfaces configured to support the carbon pills in the space. The apparatus also comprises at least two electrodes electrically coupled to the at least two conductive surfaces. The apparatus also comprises a power source connected to the electrodes for passing a current through the electrodes to convert the carbon pills to graphene. Carbon pills for graphene conversion are also provided, comprising a first carbon material for synthesis into graphene by Joule heating. The first carbon material is compressed from a powder state into a tablet. The carbon pills include a second material for at least one of binding the first carbon material from the powder state into the tablet and improving the electrical conductivity of the first carbon material.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments disclosed herein relate to the production of graphene, and in particular to methods, apparatus, and carbon pills for producing graphene. [Background technology]

[0002] Introduction Graphene can be produced by the transformation of carbon-based powder materials through Joule heating. The carbon-based powder is packed into a small container in a quartz tube, and a voltage is applied across the powder material via metal (copper, copper wool, brass) electrodes. However, powder storage, powder transportation, and powder packing into the tube (powder confinement) pose several challenges for industrial applications, making it impractical for mass production of graphene.

[0003] Furthermore, quartz tubes that can be used for Joule heating are cost-inefficient because they deteriorate and become contaminated when the carbon powder comes into contact with the quartz during the Joule heating process. Furthermore, quartz tubes must be discarded after a single use, which can significantly increase the cost of producing graphene on an industrial scale. Furthermore, the copper wool used as an electrode also deteriorates during the process, further increasing the cost of graphene production. Furthermore, the use of metal electrodes, such as copper and brass, that come into direct contact with graphene can add metal contaminants to the resulting graphene powder.

[0004] Therefore, there is a need for new cost-effective methods, products, and apparatus for producing graphene on an industrial scale. Methods, products, and apparatus for producing graphene that preserve the quartz used during synthesis could reduce costs. Additionally, there is a need for products, methods, and apparatus that improve the storage, transportation, and handling of materials required for graphene production, thereby enabling low-cost industrial production of graphene. Summary of the Invention

[0005] overview According to some embodiments, an apparatus for converting carbon pills to graphene is provided, the apparatus comprising a space between at least two conductive surfaces. The conductive surfaces are configured to support at least one carbon pill in the space. The apparatus comprises at least two electrodes electrically coupled to the at least two conductive surfaces. The apparatus comprises a power source connected to the electrodes to apply a current to the electrodes to convert the at least one carbon pill to graphene.

[0006] The apparatus may include a shield disposed around the space and configured to block powder that strays from the carbon pill without contacting the at least one carbon pill.

[0007] The device may include a force sensor for detecting a compressive force applied to the at least one carbon pill.

[0008] The device may comprise a resistance sensor for measuring the electrical resistance of the at least one carbon pill.

[0009] The apparatus may provide that the at least two conductive surfaces are coupled to a compression spring that applies a compressive force to the conductive surfaces to suspend the at least one carbon pill in space.

[0010] The device may provide that the conductive disc is a graphite disc.

[0011] The apparatus may provide that the shield is made of quartz.

[0012] The device may provide a conductive surface that is resilient at high temperatures.

[0013] The device may provide a conductive surface operating at high temperatures above 900°C.

[0014] The device may provide that the at least one carbon pill is a plurality of carbon pills.

[0015] Turbostratic graphene may be produced by the apparatus.

[0016] According to some embodiments, a method for synthesizing graphene is provided, comprising compressing at least one carbon pill between two electrodes. The at least one carbon pill comprises a first carbon material for synthesizing graphene by Joule heating. The at least one carbon pill also comprises a second material for at least one of binding the first carbon material from a powder state to a tablet state and improving the electrical conductivity of the first carbon material. The method also comprises passing an electric current through the at least one carbon pill. The method also comprises primarily converting the first carbon material to graphene.

[0017] The method may provide that passing an electric current through the at least one carbon pill includes passing an electric current through the at least one carbon pill at a low voltage to remove moisture and volatiles from the at least one carbon pill. Passing an electric current through the carbon pill may also include passing another electric current through the carbon pill at a high voltage to convert the first carbon material to graphene.

[0018] The method may provide that the current flows continuously between a low voltage and a high voltage.

[0019] The method may provide that the low voltage is between 80V and 100V.

[0020] The method may provide that a low voltage heats at least one carbon pill to a temperature between 400°C and 800°C.

[0021] The method may provide that the high voltage is between 160V and 400V.

[0022] The method may provide that the current flows for between 50 milliseconds and about 1 second.

[0023] The method may provide that the high voltage heats the pill to between 2800°C and 3000°C.

[0024] The method may provide that the at least one carbon pill is compressed with a force of between 20N and 60N.

[0025] The method may include positioning a shield to block stray powder from the carbon pill, wherein the shield does not physically contact the carbon pill.

[0026] The method may provide that the shield is quartz.

[0027] The method may include removing unconverted carbon from the graphene.

[0028] The method may provide that the at least one carbon pill is a plurality of carbon pills.

[0029] Turbostratic graphene may be produced by this method.

[0030] According to some embodiments, a carbon pill for graphene conversion is provided, comprising a first carbon material for synthesis into graphene by Joule heating, the first carbon material being compressed from a powder form into a tablet, and a second material for at least one of binding the first carbon material from the powder form into the tablet and improving the electrical conductivity of the first carbon material.

[0031] The carbon pill may provide a second material to bind the first carbon material from powder form to tablet form.

[0032] The carbon pill may provide a second material to enhance the electrical conductivity of the first carbon material.

[0033] The carbon pill may provide that the first carbon material comprises at least one of the group consisting of petroleum coke, tire carbon black, metallurgical coke, plastic ash, ground coffee, and anthracite.

[0034] The carbon pill may provide that the second material is for binding the first carbon material from powder to tablet form and includes at least one of the group consisting of ground coffee, corn starch, pine bark, polyethylene microwax, wax, Kemplex 690, cellulose, naphthenic oil, asphaltenes, and Gilsonite.

[0035] The carbon pill may provide that the second material is for improving the electrical conductivity of the first carbon material and includes at least one of the group consisting of petroleum coke, tire carbon black, carbon black, metallurgical coke, turbostratic graphene, and carbon nanotubes.

[0036] The carbon pills may have a density of about 0.7 to 1.4 g / cc.

[0037] The carbon pill may have a conductivity of about 16 to 140 mS / m.

[0038] The carbon pill may include a lubricious additive material to aid in the flow and compaction of the first carbon material.

[0039] The carbon pill may provide that the lubricious additive comprises at least one of the group consisting of microcrystalline cellulose, dicalcium phosphate, magnesium stearate, and silicon dioxide.

[0040] The carbon pills may be provided that the carbon pills have a shape that belongs to the geometric group of cylinder, disk, rectangle, hexagon, polygon, donut, and combinations thereof.

[0041] The carbon pill may be provided such that its shape includes at least one hollow structure connecting one side of the carbon pill to the other side of the pill.

[0042] The carbon pills may be provided in shapes including the group of hollow cylinders, hollow disks, and hollow hexagons.

[0043] The carbon pill may provide that at least one end face of the carbon pill is primarily flat.

[0044] The carbon pill may provide that at least one end face of the carbon pill belongs to the group of concave and convex.

[0045] Turbostratic graphene may be synthesized from carbon pills.

[0046] According to some embodiments, an apparatus for converting carbon pills to graphene is provided, the apparatus including at least two electrodes, the electrodes operating at an elevated temperature, the electrodes configured to support the carbon pills, and a power source connected to the electrodes for passing a current through the electrodes to convert the carbon pills to graphene.

[0047] The device may provide that the electrode comprises at least two portions, at least one portion being metal and at least a second portion being graphite.

[0048] The apparatus may provide that the metal portion is a high temperature metal from the group consisting of brass, copper, tungsten, titanium, stainless steel, stainless steel alloys, molybdenum, tantalum, nickel, alloys and combinations thereof.

[0049] The device may provide that the second portion is a metal carbide high temperature material.

[0050] The device may provide for the electrodes to operate at temperatures above 1000°C.

[0051] The device may provide that the electrodes have a shape belonging to the geometric group of cylinder, disk, rectangle, hexagon, polygon, cone, flattened cone and combinations thereof.

[0052] The device may provide that the sides of the electrodes supporting the carbon pills are predominantly flat.

[0053] The device may provide that the side of the electrode supporting the carbon pill includes at least one of a concave surface and a convex surface.

[0054] The device may provide that the electrode further comprises a clamp configured to pass a high density current from the planar surface electrode to the cylindrical surface electrode.

[0055] The device may be provided enclosed within a housing.

[0056] The apparatus may provide that the enclosure is under vacuum.

[0057] The apparatus may provide that the enclosure is filled with a gas from the group of nitrogen, argon, helium, oxygen and combinations thereof.

[0058] The device may provide that the housing is made from a group of materials including plexiglass, polycarbonate, polyvinyl chloride, aluminum and stainless steel.

[0059] According to some embodiments, a method for synthesizing graphene is provided, comprising compressing a carbon pill between two electrodes. The carbon pill comprises at least one carbon material, at least one powder binder material, and at least one conductivity-enhancing material. The method also comprises passing an electric current through the pill. The method also comprises primarily converting the at least one carbon material to graphene.

[0060] According to some embodiments, turbostratic graphene material is provided, where the turbostratic graphene is synthesized by Joule heating of carbon pills.

[0061] Turbostratic graphene may provide that the carbon pills include at least one carbon material and at least one binder material.

[0062] Turbostratic graphene may provide that the carbon pills include at least a carbon material and at least one conductivity-enhancing material.

[0063] Turbostratic graphene may provide that the carbon pills include at least one carbon material, at least one binder material, and at least one conductivity-enhancing material.

[0064] 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]

[0065] The drawings included herein are intended to illustrate various examples of the articles, methods, and apparatuses herein.

[0066] [Figure 1] FIG. 1 is a perspective view of a carbon pill produced by compressing a first carbon material and a second material in a press tool, according to one embodiment.

[0067] [Figure 2A] FIG. 2A is a front view of one embodiment of a press for producing high aspect ratio carbon pills.

[0068] [Figure 2B] FIG. 2B is a cross-sectional view of a press according to one embodiment.

[0069] [Figure 3]FIG. 3 illustrates a 15 mm outer diameter carbon pill 305 made from 30% binder and 70% carbon-based material using the press of FIGS. 2A and 2B, according to one embodiment.

[0070] [Figure 4] FIG. 4 is a diagram illustrating an apparatus for producing carbon pills, according to one embodiment.

[0071] [Figure 5] FIG. 5 is a top view of a carbon pill produced by an automated pill press, according to one embodiment.

[0072] [Figure 6] FIG. 6 illustrates an apparatus for producing carbon pills through an extrusion process, according to one embodiment.

[0073] [Figure 7] FIG. 7 is a side view illustrating an apparatus for converting carbon pills into graphene, according to one embodiment.

[0074] [Figure 8] FIG. 8 is a side view of an apparatus for converting carbon pills to graphene including a force sensor and a resistance sensor, according to one embodiment.

[0075] [Figure 9] FIG. 9 shows a flowchart illustrating a method for synthesizing graphene, according to one embodiment.

[0076] [Figure 10] FIG. 10 is a flowchart illustrating a method for producing graphene, according to one embodiment.

[0077] [Figure 11] FIG. 11 illustrates an apparatus for carrying out the method of converting carbon pills into graphene, according to one embodiment.

[0078] [Figure 12] FIG. 12 illustrates an apparatus for performing the method of converting carbon pills to graphene without the use of graphite disks, according to one embodiment.

[0079] [Figure 13] FIG. 13 illustrates an apparatus for carrying out the method of converting flat carbon pills into graphene without graphite disks, according to one embodiment.

[0080] [Figure 14] FIG. 14 shows Raman spectroscopy measurements of graphene produced from samples of carbon pills in Table 3, according to one embodiment.

[0081] [Figure 15] FIG. 15 illustrates an apparatus for converting carbon pills to graphene after Joule heating, according to one embodiment.

[0082] [Figure 16] FIG. 16 illustrates an apparatus for carrying out the method of converting cylindrical carbon pills into graphene, according to one embodiment.

[0083] [Figure 17] FIG. 17 illustrates an apparatus for carrying out a method for converting cylindrical carbon pills to graphene without a cover tube, according to one embodiment.

[0084] [Figure 18] FIG. 18 illustrates exploded electrodes of an apparatus for converting carbon pills to graphene, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0085] Detailed Description Various devices or processes are described below to provide examples of each claimed embodiment. The embodiments described below do not limit any claimed embodiment, and any claimed embodiment may be directed to a process or device different from those described below. Also, a claimed embodiment is not limited to a device or process having all of the features of any one device or process described below, or to features common to multiple or all of the devices described below.

[0086] Provided herein, according to one embodiment, are carbon pills that can be easily stored, transported, and handled without the need for containment, and are suitable for Joule heating to convert the carbon in the carbon pills to graphene.

[0087] Provided herein, according to one embodiment, is an apparatus for converting carbon pills into graphene, including thermoelastic electrodes and compression springs that hold the pills in place and can apply a voltage to the pills without additional support or confinement.

[0088] Provided herein, according to one embodiment, is a method for synthesizing graphene from carbon pills by Joule heating the pills at temperatures between 2800 and 3000°C. The method for synthesizing graphene from carbon pills produces primarily few-layer turbostratic graphene. Turbostratic graphene is multiple graphene layers that are misoriented relative to each other. Therefore, these layers are not AB-stacked. The graphene layer structure of turbostratic graphene allows graphene powder to be easily dispersed in liquids. Easier graphene dispersion allows for the creation of better graphene compositions.

[0089] Turbostratic graphene is graphene with little order between the graphene layers. Other terms that may be used include misoriented, twisted, rotated, rotated-faulted, and weakly bonded. The rotated stacking of turbostratic graphene relaxes interlayer bonds and increases interplanar spacing, resulting in superior physical properties compared to competing graphene structures at comparable weights. Subtle differences in the stacking direction of adjacent layers can result in significant differences in product performance. An important performance advantage of turbostratic graphene is the tendency for multilayer graphene structures to separate into a small number of individual graphene layers, which tend not to recoupling. The turbostratic nature of graphene can be observed and confirmed by Raman analysis.

[0090] The flash joule heating synthesis method and compositions thereof are described in Patent Cooperation Treaty Application having International Publication Number WO2020 / 051000A1 to Tour et al., having an international publication date of March 12, 2020, which is incorporated herein by reference in its entirety.

[0091] Example 1 – Carbon pill for graphene conversion Provided are carbon pills for graphene conversion, comprising a first carbon material for synthesis into graphene by Joule heating, the first carbon material being compressed from a powder form into a tablet, and a second material for binding the first carbon material from the powder form into the tablet or for improving the electrical conductivity of the first carbon material.

[0092] Referring to Table 1, the parameters of one embodiment of carbon pills for graphene conversion are shown. [Table 1]

[0093] The first carbon material may comprise a substance that can be converted to graphene by Joule heating. The first carbon material for producing carbon pills for conversion to graphene by Joule heating includes any one or more of green petroleum coke, calcined petroleum coke, carbon black, carbon black from recycled tires, metallurgical coke, coal, anthracite, ash from recycled plastics, used coffee grains, and any combination thereof.

[0094] The first carbon material can be compressed into a pill shape with the aid of a die and press without any other additives. Exemplary materials include green pet coke and used coffee grounds. Thus, some materials can be both the first carbon material and the second binder material.

[0095] Some forms of carbon materials do not stick well together and do not have the mechanical strength to handle the pills. A second material to bind the first carbon material may be added to the carbon powder before compressing it into a pill to help form and maintain its shape. Binders include lignans or lignan-containing materials such as coffee.

[0096] The first carbon material may be compressed into a pill, but may not have sufficient electrical conductivity to undergo Joule heating at voltages ranging from 90 V to 600 V, requiring impractically high voltages. A second material to improve the electrical conductivity of the first carbon material may also be added to the carbon powder before being compressed into a pill. The conductive additive material may include any one or more of carbon black, tire carbon black, calcined petroleum coke, metallurgical coke, single-walled and multi-walled carbon nanotubes, graphene, and any combination thereof.

[0097] If the first carbon material does not adhere well and does not have sufficient electrical conductivity to be easily Joule heated, a second material, a binder material, can be added to aid in pill formation, and another material, a conductive additive material, can be added to increase the electrical conductivity of the pills. The first carbon material can include one or more of plastic ash, pyrolyzed plastic, and raw ground plastic powder.

[0098] Dopant impurities may be intentionally added to the pills to form improved graphene materials. Dopants include any one or more of Fe, Ni, B, or F (via compounds). Examples of improved properties include magnetism, thermal and electrical conductivity, and functionalization.

[0099] Referring to Table 2, provided here is a list of carbon materials, binders, and conductive additives and their mass utilization in carbon pills for graphene conversion. [Table 2]

[0100] A method for producing a carbon pill is provided, which includes placing a first carbon material and a second material in powder form into a die space. The method also includes compressing the first carbon material and the second material from powder form into a tablet form with a press tool.

[0101] 1, there is shown a carbon pill 100 according to one embodiment, produced by compressing a first carbon material and a second material in a press tool. Carbon powder is compressed with the aid of a die, punch, and hydraulic press into a tablet suitable for Joule heating.

[0102] The ratio of carbon powder to binder can be measured using a high-precision scale. The carbon and binder are first ground, either individually or together, in a mortar and pestle for several minutes. On a larger scale, a ball mill is used to grind the powders into particles ranging from mm to 5 microns. The powders are mixed uniformly and loaded into a die. A pin is then inserted into the die, and the set is placed under the head of a hydraulic press. The hydraulic press applies a pressure of 2 to 10 tons and holds that pressure for 1 second to 5 minutes to form a pill. The carbon pill is then ejected from the die.

[0103] In one embodiment, the transformation of graphene tablets requires that they be stored, handled, and transported without breaking. Preferred pill dimensions may be 10-20 mm in diameter and 4-50 mm in length. Preferred pill densities may be about 0.7-1.4 g / cc. The pills may have electrical conductivity of about 16-140 mS / m (2-20 Ω across the length of the pill). The pills may withstand a clamping force of about 2-10 kg (20-100 N) before being processed. The pills may be heated to 600°C for several seconds multiple times without disintegrating.

[0104] Exemplary carbon powders that can be the first carbon material for the pill include, but are not limited to, carbon black, tire carbon black, and pet coke (green and calcined). Exemplary second materials for binding the first carbon material for the pill include, but are not limited to, coffee, pine bark, green pet coke, PE microwax, wax, and the commercially available carbon binder Chemplex 690.

[0105] Carbon powder with a particle size of 100-200 microns may be used in the pill. The pill composition may include 80% of a first carbon material and 20% of a second material to bind the first carbon material.

[0106] Referring to Figure 2A, shown therein is a front view of one embodiment of a press 200 for producing high aspect ratio carbon pills. Figure 2B is a cross-sectional view of the press 200 according to one embodiment. The 20 mm die 205 used to press the 20 mm outer diameter carbon pill 210 has a high aspect ratio of outer diameter to length, ranging from 1:0.5 to 1:5.

[0107] The press 200 includes a die cavity 215 in which the first carbon material and the second material are placed. The cavity 215 is surrounded by a wall 220 that prevents the powder from escaping during pressing. The pill is compressed between a pin 205 and a base 225.

[0108] The compression force required to create a carbon pill 210 is 1 cm2 2 The optimum compression force is 1 to 12 tonnes per cm. 2 That's about 5 tons of force per unit.

[0109] Referring to Figure 3, there is shown a carbon pill 305 having an outer diameter of 15 mm made from 30% binder and 70% carbon-based material using the press of Figures 2A and 2B, according to one embodiment. The carbon pill 305 has a resistance of approximately 100 Ω to 1 kΩ, depending on the composition of the pill material and the compression force.

[0110] Carbon powder can be compressed into pills suitable for graphene conversion by Joule heating with the aid of a die, punch, and vice. In one example, a die and punch set typically used in pharmaceutical tablet machines was used to produce carbon pills. A set with an inner diameter of 10 mm was used. The pins in the set have elliptical (spherical cup) ends to ensure the compressed pills are elliptical.

[0111] Finely ground coffee, such as Turkish coffee, was used as the starting material to prepare the coffee. The coffee grounds may then be baked at 400°F for several hours to remove moisture. 10% by weight of carbon black was added to the dried coffee and mixed in a mortar to achieve a fine blend.

[0112] Referring to FIG. 4, an apparatus 400 for making carbon pills is shown, according to one embodiment. Powdered carbon material is poured into a die 405 and sealed with two pins 410. The assembly is compressed using a machine shop vise 415. The compression force is estimated to be approximately 250 kg (2500 N). A carbon pill 420 is produced from the compression of the carbon material and the second material. For 200 mg of material, the resulting carbon pill is approximately 3.5 mm in height and approximately 10 mm in outer diameter. Manually produced carbon pills 420 are produced at a much slower speed when using an automated press. For commercial production, a tablet compression machine may be used. Also, a die set with a diameter of 6 mm to 25 mm may be used.

[0113] In some embodiments, an automated machine is used to compress the carbon pills. The automated machine is a motor-driven single-punch machine that can operate in manual mode and automatically at a rate of 2000 tablets per hour. The operation is entirely mechanical, with upper and lower cams synchronously driving upper and lower pistons. An electric motor provides power to rotate the crank. The piston pressure can be adjusted from zero to 5 tons. The tablet die can be 6 mm deep and up to 20 mm in diameter.

[0114] During the dispensing of powder ingredients in a typical pill manufacturing process, powder flow is by gravity and agitation, making it very efficient. The dispensing arm slides firmly over the hole to be filled, moving back and forth. The arm wipes away excess material without losing powder, ensuring the cavity is never overfilled.

[0115] Material flowability and compression cohesion are powder properties that can be tailored when manufacturing pills. An advantage for better powder dispensing is to utilize custom CAM to provide more powder shaking and ensure the die is completely filled with powder before compression. It is also possible to use a stepper motor with an encoder to drive the motor and add custom process control using existing CAM. Using a stepper motor allows for adding automation to a highly mechanical system.

[0116] In some embodiments, fresh, dry binder such as ground coffee may be compressed into tablets without additives at 5 tons of pressure and stored and transported in Ziploc® bags with good handling. The coffee tablets are still porous and may crumble under heavy hand pressure.

[0117] Also, coffee-based carbon pills with some ambient moisture may be compressed into tablets at 5 tons of pressure without any additives. Coffee-based carbon pills with some ambient moisture compress slightly better than dry coffee powder, but the pills may stick to the die and the powder flow is not as good as the dry powder.

[0118] In one embodiment, the first carbon material is a powder that is dried in an air or vacuum oven with a static or mixing arm to remove or reduce the moisture in the powder, allowing for better powder flow and therefore faster pill production.

[0119] Referring to FIG. 5, there is shown a carbon pill 500 produced by an automatic pill press according to one embodiment. The carbon pill 500 was produced by an automatic pill press using 95% undried coffee and 5% carbon black. Compression using carbon black is easier than with 100% coffee powder. The higher the weight percentage of carbon black, the better the carbon pill compression. The coffee and carbon black powder flows better and requires less force to press into a pill than with 100% coffee. The carbon pills 500 are 10 mm in diameter and 5 mm in height. Each pill weighs between 0.25 g and 0.4 g. The resistance of the compressed pills is approximately 1.2 kΩ. The pill resistance can be reduced by increasing the conductivity of the powder, such as by increasing the weight percentage of carbon black in the powder mixture. The optimal pill resistance is between 20 Ω and 1 kΩ.

[0120] The automated pill press process can also be applied to any other type of carbon material suitable for graphene conversion and any combination of such materials. Additionally, the automated pill press process can be applied to any combination of the ingredients listed in Table 1.

[0121] Additives that aid in pill flow (lubrication) and compression, such as additives used in the food industry, can also be used in the production of carbon-based pills for the production of graphene by Joule heating. Lubricious additive materials that can be used in carbon pills include, but are not limited to, microcrystalline cellulose (MCC), dicalcium phosphate, magnesium stearate, and silicon dioxide. A combination of lubricious additives can be used, or a single lubricious additive, such as MCC, can be used. Starch can also be used as both a binder and a lubricious additive. For example, 5% by weight of the lubricious additive can be added to the powder stream.

[0122] The compression of the air trapped in the powder exerts pressure on the die. To avoid stress on the die, a two-punch machine is used, which first pre-compresses the powder and then compresses the pre-compressed powder into tablets. The two-punch machine measures the compression and has pre-compression and main compression steps. In some embodiments, a two-punch machine with maximum capacity can produce 15,000 tablets per hour.

[0123] By controlling air pockets with double compression and therefore reducing stress on the die, in some embodiments the stainless steel die is replaced with a quartz die so that Joule heating of the carbon-based material can occur during compression. The Joule heating step may alternatively be performed after compression.

[0124] An example of a high-speed pill-making machine can produce 200,000 carbon pills per hour. If each pill produced by the machine weighs 0.25g and the Joule heating process is balanced with the machine's pill production, this process can produce approximately 50kg of graphene per hour.

[0125] Referring to Figure 6, there is shown an apparatus for producing carbon pills through an extrusion process, according to one embodiment. Powder 625 is continuously charged into a funnel 605 into a powder extruder 610. The extruder 610 compresses the powder 625 and ejects the material through a nozzle 630 or die with the desired dimensions, and the carbon pills 620 are cut to specific lengths using a rotating blade 615.

[0126] The carbon pill may be any shape formed by compressing carbon powder. In some embodiments, the carbon pill is cylindrical with a circular cross section and flat ends. In other embodiments, the pill is rectangular with a rectangular cross section. In other embodiments, the carbon pill is brick-shaped. In other embodiments, the carbon pill has at least one hole in the middle. In other embodiments, the carbon pill has multiple holes distributed across its cross section. The purpose of the holes is to allow for more uniform heat distribution and gas escape. The pill may be, for example, a hollow disk. The ends of the pill may be, but are not limited to, flat, concave, convex, or may have a conical end for better pill clamping.

[0127] Example 2 - Apparatus for converting carbon pills into graphene Provided herein is an apparatus for converting carbon pills to graphene, comprising at least two conductive surfaces configured to support the carbon pills within a space between them. The conductive surfaces include at least two electrodes electrically coupled to the at least two conductive surfaces. The apparatus also includes a power source connected to the electrodes to apply a current to the electrodes to convert the carbon pills to graphene.

[0128] In some embodiments, the device also includes a shield disposed around the space and configured to block powder escaping from the carbon pill without contacting the carbon pill. The shield may be made of quartz. The device may also include a force sensor for detecting a compressive force applied to the carbon pill and a resistance sensor for measuring the electrical resistance of the carbon pill during filling and processing.

[0129] In some embodiments, the two conductive surfaces are coupled to a compression spring to apply a compressive force to the conductive disks, suspending the carbon pill in space. The conductive surfaces may be graphite disks.

[0130] This apparatus may be used to produce turbostratic graphene by Joule heating carbon pills.

[0131] In some embodiments, an apparatus for converting carbon pills to graphene includes graphite-based thermoelastic electrodes and compression springs that hold the pills in place and apply a voltage to the pills without additional support or confinement. The present disclosure also discloses a process for converting carbon-based pills to graphene with the aid of Joule heating of the pills.

[0132] Referring to FIG. 7 , an apparatus 700 for converting a carbon pill 715 to graphene is illustrated, according to one embodiment. The carbon pill 715 is suspending itself by two spring-compressed graphite electrodes 725, which have excellent electrical conductivity and can withstand high temperatures. The graphite material does not contaminate the graphene produced during Joule heating, even at temperatures as high as 3000° C. The graphite electrodes 725 receive power from a brass electrode 730, which slides freely through a pair of rod bearings 710, 740. One of the rod bearings 710 is grounded, while the other rod bearing 740 slides. A pair of compression springs 735 pushes against the bearings 710, 740, pushing against the brass 730 and graphite electrodes 725 and compressing the carbon pill 715. While the apparatus 700 is illustrated using compression springs 735 to suspend the carbon pill 715, any mechanism sufficient to suspend the carbon pill during Joule heating may be used. This device is also sometimes called an electric vise.

[0133] The Joule heating process that converts carbon to graphene lasts from 1 millisecond to 5 seconds, during which the peak temperature reaches 3000°C in 1 to 100 milliseconds. However, due to radiative cooling, most of the heat from the pill is dissipated to the surrounding environment and other components of the device 700, except for the graphite electrode 725, which is in direct contact with the pill 715. Other components of the device can reach peak temperatures of 200°C to 1500°C. Therefore, other parts of the device must be rated for higher temperatures.

[0134] A power supply 705 provides power to the device 700 for joule heating of the carbon pill 715. The device 700 also includes a shield 720, which is a half quartz tube.

[0135] In some embodiments, the body of the device 700 is made from 3D-printed plastic parts and utilizes a linear stage to move one electrode relative to the other at a predetermined force. The clamping force of the pill 715 may be adjusted with a set screw and monitored using a disk force sensor. The device 700 also includes a shield 720, a quartz tube that does not come into contact with the carbon pill 715; its purpose is to collect any dust generated during the Joule heating process that converts the carbon pill 715 to graphene.

[0136] Because the protective quartz tube does not come into contact with the carbon pill 715, the quartz tube does not deteriorate and can be used multiple times. In some embodiments, the quartz tube is replaced with a half quartz tube. The half quartz tube is cut longitudinally to deflect powder scattered from the carbon pill 715 downward into a collection bin (not shown). The bottom of the carbon pill 715 is open to the collection bin.

[0137] 8, illustrated therein is an apparatus 700 according to one embodiment for converting carbon pills 715 to graphene, including a force sensor 810 and a resistance sensor 805. The force sensor 810 may be, but is not limited to, a disc force sensor sandwiched between a sliding bearing 740 and a compression spring 735. When the sliding bearing 740 compresses the spring 735, the intervening force sensor 810 detects the force applied to the carbon pills 715.

[0138] The pill 715 is compressed with a force ranging from 20 N to 100 N. Additionally, the device incorporates a resistance sensor 805 that measures the resistance of the carbon pill 715 as a function of pill compression force. In some embodiments, the resistance sensor 805 is isolated from the high-power circuitry via a manual or automatic switch to protect the circuitry from high power. Pill resistance can be measured before processing, during processing steps, and after Joule heating conversion. Pill resistance ranges from 1 to 500 Ω. The presence of the force sensor 810 and resistance sensor 805 allows for automation of the device 700. In one automation example, a motor slides the bearing 740 until the desired force or resistance is achieved.

[0139] In some embodiments, multiple carbon pills may be stacked together to create a larger mass, thus accelerating graphene production. For example, five 1-gram carbon pills may be stacked to create a total 5-gram carbon pill sample. The carbon pills may be in contact with each other, or graphite disk electrodes may be inserted between them to create a more dispersed heating profile.

[0140] Joule heating of the carbon pills can be carried out in air, in a vacuum chamber, or in a gas chamber filled with oxygen, nitrogen, argon, fluorene, or other gases that improve the properties of the resulting graphene.

[0141] Example 3 - Method for synthesizing graphene 9, shown therein is a flowchart illustrating a method 900 for synthesizing graphene, according to one embodiment. The method 900 includes, at 905, compressing a carbon pill between two electrodes. The carbon pill includes a first carbon material for synthesizing graphene by Joule heating and a second material for binding the first carbon material from a powder state to a tablet state or for improving the electrical conductivity of the first carbon material.

[0142] The method 900 also includes, at 910, passing an electric current through the carbon pill.

[0143] The method 900 also includes, at 925, converting the primarily first carbon material into graphene.

[0144] Method 900 may optionally include passing a low voltage current through the carbon pill to remove moisture and volatile materials from the carbon pill at 915. The passing of the low voltage current may optionally be repeated at 915 until all moisture and volatile materials are removed from the carbon pill.

[0145] Method 900 may optionally include passing another current at high voltage through the carbon pill to convert the first carbon material to graphene, at 920. The passing of the high voltage current may optionally be repeated, at 920, until all of the carbon material has been converted to graphene.

[0146] The method 900 may optionally include, at 930, removing unconverted carbon from the graphene.

[0147] In some embodiments, a 1 g carbon pill with an outer diameter of 15 mm and a length of 5 mm is clamped in the apparatus of Example 2 with a clamping force of 20 N to 60 N and a pill resistance of 2 to 100 Ω. The voltage applied to the pill can be direct current, alternating current, or any combination thereof. In the preconditioning step, a low voltage of 80 to 100 V is applied to the pill for 500 milliseconds. The preconditioning step is repeated as necessary based on the properties of the initial material. Due to the resistance of the carbon pill, the voltage induces a current, and the sample is rapidly heated to a temperature of 400 to 800 °C. At temperatures of 400 to 800 °C, most of the volatiles and moisture contained in the carbon pill are removed. If the carbon pill is too dense, the pressure of the outgassing may destroy the carbon pill. In preferred carbon pills, voids exist within the carbon pill, allowing outgassing to escape without destroying the pill.

[0148] In the final step, a voltage of 160 V to 400 V is applied to the pretreated carbon pill for a time period of 50 milliseconds to 1 second. During Joule heating of the pill, the resistance dramatically decreases, and therefore the current through the pill dramatically increases to between 1500 and 3000 A. The pill's temperature reaches 2800 °C to 3000 °C, during which time the carbon is converted to graphene. This final step may be repeated several times depending on the composition and size of the carbon pill. Most of the energy in the carbon pill is removed by radiative cooling, also known as an optical flash, and the carbon pill is rapidly cooled to room temperature, while the carbon material is converted to graphene. In some cases, the graphene remains as a deformed pill; in other cases, the pill disintegrates into powder. In some embodiments, the graphene has a light gray color, indicative of the presence of graphene.

[0149] In some embodiments, the pre-treatment and final treatment steps are integrated into a single Joule heating step, where the Joule heating temperature profile is controlled by controlling the voltage to the electrodes. The carbon pill is heated to a low temperature and then to a high temperature, all in one continuous heating step. The temperature profile can be controlled using a Proportional-Integral-Differential (PID) control loop, where the input is the pill temperature measured by a pyrometer and the output is the voltage to the electrodes, which provides a corresponding current for a given pill resistance. This current induces Joule heating of the pill. The PID control loop can be optimized using predictive models and machine learning.

[0150] In a downstream processing step, the graphene pills or powder are sieved to remove large particles that may represent carbon that has not been converted to graphene. In some embodiments, the graphene powder is soft and can be easily pushed through a sieve and may be easily crushed into smaller particles. In some configurations, the hard-to-crush particles are not graphene and can be easily filtered out. The final graphene particles may range from 1 to 150 microns, depending on the starting size of the carbon material particles.

[0151] Referring to FIG. 10, shown therein is a flow chart illustrating a method 1000 for producing graphene according to one embodiment. The method 1000 includes, at 1005, forming a carbon pill. The pill preferably has an outer diameter of 15 mm and a thickness of 4-5 mm. The carbon pill is preferably formed using a compressive force of 5 tons. The carbon pill is preferably clamped with a force of 20 N to 60 N in an apparatus for converting the carbon pill to graphene. The carbon pill preferably has a resistance of 2 to 100 Ω.

[0152] The method 1000 includes pretreating the carbon pill at 1010 by passing a current through the carbon pill for 500 milliseconds at a voltage between 80 V and 100 V. The pretreatment 1010 is repeated until all moisture and volatiles are removed from the carbon pill.

[0153] The method 1000 also includes, at 1015, Joule heating the carbon pills by passing a current through the carbon pills for 0.5 to 1 second at a voltage between 160 V and 400 V. This process is repeated until all of the carbon pills are converted to graphene.

[0154] The method 1000 also includes, at 1020, post-processing the produced graphene by sieving the graphene through a #100 mesh and grinding the graphene in a ball mill.

[0155] The production of graphene, particularly turbostratic graphene, from carbon pills by use of the apparatus of Example 2 can be scaled to produce large quantities of graphene at rates from 1 kg per day to 1 ton per day.

[0156] Referring to FIG. 11, an apparatus 1100 for performing a method for converting carbon pills 1120 to graphene is shown, according to one embodiment. The carbon pills 1120 are compressed between two graphite disks 1110 connected to brass electrodes 1105 within a quartz tube 1115 with an inner diameter of 10.5 mm. A gap exists between the carbon pills 1120 and the walls of the quartz tube 1115. Because the carbon pills 1120 are elliptical, the graphite disks 1110 contact the pills' tangents. The carbon pills 1120 are pretreated with a low-voltage current until their resistance drops from 20-40 Ω to approximately 1.5 Ω. The pills maintain their shape during pretreatment. After Joule heating with a high-voltage current, the carbon pills 1120 decomposed into graphene powder, and a small amount of powder escaped from the tube. A fine powder remained along the inner wall of the quartz tube 1115, which was then cleaned with Kimwipes and alcohol. The final bulk powder material was graphene.

[0157] Referring to Figure 12, there is shown an apparatus 1200 according to one embodiment for performing a method for converting carbon pills 1205 to graphene without using a graphite disk. The graphene conversion process is the same as that of the apparatus 1100 of Figure 11, except that the brass electrode 1215 is in direct contact with the carbon pill 1205. Also, there is a gap between the carbon pill 1205 and the wall of the quartz tube 1210. The Joule heating current is up to 1459 A. Because of the direct contact with the carbon pill 1205, the brass electrode 1215 may melt during Joule heating.

[0158] Referring to FIG. 13 , there is shown an apparatus 1300 according to one embodiment for carrying out a method for converting a flat carbon pill 1305 to graphene without a graphite disk. The apparatus 1300 is shown for Joule heating the carbon pill 1305. 250 mg of a first carbon material (90% coffee and 10% carbon black) is pressed into a tablet and pre-treated until the pill resistance is 2 Ω or less. The pill 1310 maintains its shape after Joule heating but loses some mass, resulting in a 200 mg pill. The pre-treated 200 mg is crushed in a mortar and pressed into a pill again. This pill is placed in a quartz tube 1310 with an inner diameter of 10.5 mm, and the pill is only in contact with a brass screw 1315. After some additional pre-treatment, the carbon pill 1315 is intact. After the pill 1305 is Joule heated, it transforms into graphene powder and has gray matter throughout its volume. Despite there being plenty of voids for the carbon to escape, not much graphene is lost during flashing. A typical final graphene mass is 96 mg for the coffee-based carbon pill 1305 (starting from a 200 mg pill).

[0159] In one example process, the sample is first pressed into a pill and then inserted into an apparatus for converting the carbon pill to graphene. During the Joule heating process, the carbon pill is pre-treated at temperatures between 200°C and 1000°C to remove moisture, oils, and other volatiles, and then Joule heated at temperatures between 2600°C and 3000°C to convert the carbon to graphene.

[0160] In some embodiments, the carbon pills maintain their shape and do not crumble during pre-processing.

[0161] In some embodiments, the first carbon material is first separately pretreated to remove moisture, oil, and other volatiles, then the pretreated first carbon material is crushed and then pressed into pills. In the next step, the carbon pills from the pretreated first carbon material are inserted into an apparatus for converting carbon pills to graphene and Joule heated at temperatures between 2600°C and 3000°C to convert the carbon to graphene.

[0162] In one embodiment, after the Joule heating process converts the carbon to graphene, the carbon pills maintain their shape and do not collapse, while in another variation the pills turn into graphene powder.

[0163] Table 3 shows the properties of carbon pills for several embodiments. Two different combinations of carbon pill compositions are shown. Samples 64, 65C, 68C, 70C, 71C, and 72C have compositions of 10% carbon black and 90% coffee. Samples 73C and 74C have compositions of 70% petroleum coke and 30% pine bark. Samples with a "C" in their names were compressed into 4 mm diameter pills and converted to graphene by Joule heating in a 10 mm inner diameter quartz tube. Therefore, the gap between the pill and the quartz is 3 mm. Sample 64 is uncompressed and is used as a reference. Raman spectroscopy results in the ratio of the 2D band to the G band (2D / G). Therefore, the 2D / G ratio of the produced graphene varies from 0.7 to 1.2. These results confirm that graphene can be produced from compressed, suspended carbon pills. [Table 3]

[0164] Referring to FIG. 14 , shown therein are Raman spectroscopy measurements of graphene produced from the carbon pill samples of Table 3, according to one embodiment. The 2D / G ratio of graphene produced by Sample 64 is 1. The 2D / G ratio of graphene produced by Sample 65C is 0.7. The 2D / G ratio of graphene produced by Sample 68C is 1.2. The 2D / G ratio of graphene produced by Sample 70C is 1. The 2D / G ratio of graphene produced by Sample 71C is 1. The 2D / G ratio of graphene produced by Sample 72C is 0.4. The 2D / G ratio of graphene produced by Sample 73C is 0.9. The 2D / G ratio of graphene produced by Sample 74C is 0.7.

[0165] Referring to Figure 15, there is shown an apparatus according to one embodiment for converting a carbon pill 1505 to graphene after Joule heating. The carbon pill 1505 is made from a mixture of 70% petroleum coke and 30% pine bark and compressed into a 4 mm diameter pill with a density of 1.4 g / cc. The carbon pill 1505 is shown after Joule heating within a larger 10 mm quartz tube 1510. Some debris during the Joule heating process collects along the tube wall, but the carbon pill 1505 does not come into contact with the tube wall.

[0166] Referring to Figure 16, there is shown an apparatus 1600 according to one embodiment for carrying out a method for converting a cylindrical carbon pill 1620 into graphene. The compressed pill 1620 has a cylindrical shape to allow for better electrical contact to the graphite disk 1610 connected to the electrode 1605. The cylindrical shape, which has a smaller diameter than the inner tube, also provides a gap between the carbon pill 1620 and the tube 1615. Note that the tube 1615 does not have to be transparent.

[0167] In one embodiment, after Joule heating of the carbon pill, where the carbon is converted to graphene at temperatures between 2600°C and 3000°C, the carbon pill is cooled very quickly, preferably by radiative cooling. When the compressed carbon is in contact with a tube, the tube must be optically transparent to allow light to escape quickly and enable radiative cooling.

[0168] In one embodiment, the cover tube need not be transparent, provided that the sample-to-tube distance is long enough and there is sufficient thermal mass to allow rapid radiative heat transfer from the sample to the tube.

[0169] In one embodiment, the gap between the sample and the cover wall is 1 mm to 5 mm, and in another example, the gap is 5 mm to 100 mm. Cover tube materials include, but are not limited to, ceramic, alumina, stainless steel, or aluminum. For conductive cover tubes, electrical insulation from the electrode and sample is necessary. It may be beneficial to actively cool the cover tube to remove accumulated heat from the cover tube. Active cooling methods include forced air and water cooling of the outer wall of the cover tube.

[0170] Referring to FIG. 17 , there is shown an apparatus 1700 for performing a method of converting a cylindrical carbon pill 1715 to graphene without a cover tube, according to one embodiment. There is no cover tube near the carbon pill 1715. A graphite disk 1710 connected to an electrode 1705 directly contacts the carbon pill 1715. Radiant heat dissipates to the surroundings, allowing for rapid cooling of the graphene. A collection tray 1720 is positioned below the processing area to collect the powdered graphene. A vacuum chamber 1725 surrounds the Joule heating device and may be part of the apparatus. The vacuum chamber, also referred to as the enclosure, may be pumped to a vacuum or alternatively filled with a gas from the group consisting of nitrogen, argon, helium, oxygen, and combinations thereof. The vacuum chamber may be made from a group of materials including plexiglass, polycarbonate, polyvinyl chloride, aluminum, and stainless steel.

[0171] In one embodiment, the first carbon material is crushed and sieved to create pills made from similarly sized carbon particles. All particles may be in the 100-200 micron range. Alternatively, the carbon particles may be in the 200-300 micron range. Alternatively, the particles may be in the 300-600 micron range. Crushing and sieving the first carbon material results in a more uniform density of the carbon pills and creates voids within the pills that allow for outgassing at high temperatures without destroying the pills. Finer particle size powders tend to be more durable and produce thinner pills. Larger particle size powders tend to produce thicker pills, resulting in discontinuous phases in the carbon material. Larger particle size raw materials can be directly Joule heated without the need to pretreat the carbon material to remove volatiles.

[0172] In one embodiment, the carbon pill is made from two or more carbon powders, each with a similar particle size range, each adding different properties: one carbon species can add connectivity, while another carbon species can add conductivity to the pill.

[0173] In one embodiment, the pill is made from two or more carbon powders, one type being large (micron-sized) and uniformly sized, while the other is nanometer-sized. Each powder can add different properties. The larger carbon species may add connectivity, while the other may add conductivity to the pill. One example of this pill design is a mixture of green pet coke, which has a 200-300 micron particle size, for its high binding ability, and conductive carbon black, which has a nanometer particle size.

[0174] In one embodiment, the carbon pill is made of two or more types of carbon powder, one type having substantially round grains and another type having elongated fibers such as carbon nanotubes or carbon fibers.

[0175] Referring to FIG. 18 , an exploded view of an electrode 1800 of an apparatus for converting carbon pills to graphene is shown, according to one embodiment. The electrode has two components: a metal component 1805, such as brass, and a graphite disk termination 1810. The metal portion of the electrode can be made from a high-temperature metal from the group consisting of brass, copper, tungsten, titanium, stainless steel, stainless steel alloys, molybdenum, tantalum, nickel, alloys, and combinations thereof. The graphite disk 1810 can be threaded into the brass component 1805, or the brass component 1805 can have a surface that allows the graphite disk 1810 to make better electrical contact with the brass component 1805. The electrically conductive surface that contacts the carbon pills can be either the brass component 1805 or the graphite disk 1810 of the electrode 1800. The electrode includes a clamp 1815 configured to pass a high-density current from the flat surface electrode to the cylindrical surface electrode. In some embodiments, the brass parts are alternatively made of copper.

[0176] Although the above description provides examples of one or more devices, methods, or systems, it will be understood that other devices, methods, or systems are within the scope of the claims as interpreted by one of ordinary skill in the art.

Claims

1. 1. An apparatus for converting carbon pills into graphene, comprising: a space between at least two conductive surfaces, the conductive surfaces configured to support and conductively couple to at least one carbon pill in the space; at least two electrodes electrically coupled to the at least two conductive surfaces; a power source connected to the electrodes for passing a current through at least one carbon pill via the conductive surface coupled to the at least two electrodes to convert the at least one carbon pill into graphene. Device.

2. further comprising a force sensor for detecting a compressive force applied to the at least one carbon pill.

10. The apparatus of claim 1.

3. further comprising a resistance sensor for measuring the electrical resistance of the at least one carbon pill.

10. The apparatus of claim 1.

4. the at least two conductive surfaces are coupled to a compression spring for applying a compressive force to the conductive surfaces to suspend the at least one carbon pill in the space; 10. The apparatus of claim 1.

5. the conductive surface is a graphite disk; 10. The apparatus of claim 1.

6. 1. A method for synthesizing graphene, comprising: compressing at least one carbon pill between two electrodes, the electrodes configured to support and conductively couple to the at least one carbon pill, the at least one carbon pill comprising a first carbon material for synthesizing graphene by Joule heating and a second material for at least one of binding the first carbon material from a powder state to a tablet state and improving the electrical conductivity of the first carbon material; applying an electric current to the at least one carbon pill via the electrode; and converting the first carbon material into graphene. method.

7. Passing an electric current through the at least one carbon pill comprises: applying a low voltage current to the at least one carbon pill to remove moisture and volatile materials from the at least one carbon pill; and passing another current at high voltage through the carbon pill to convert the first carbon material into graphene. The method of claim 6.

8. the current flows continuously between the low voltage and the high voltage; the low voltage is between 80V and 100V; The high voltage is between 160V and 400V. The method of claim 7.

9. The low voltage heats the carbon pill to a temperature between 400°C and 800°C. The method of claim 8.

10. The high voltage heats the pill to between 2800°C and 3000°C. The method of claim 8.

11. Carbon pills for graphene conversion, a first carbon material for synthesis into graphene by Joule heating, the first carbon material being compressed from a powder form into a tablet configured to be supported by and conductively coupled to at least two electrodes for passing an electric current through the carbon pill; a second material for at least one of binding the first carbon material from a powder state to a tablet state and improving the electrical conductivity of the first carbon material; Carbon pill.

12. The second material is for binding the first carbon material from a powder state to a tablet state. The carbon pill of claim 11.

13. the second material is for improving the electrical conductivity of the first carbon material; The carbon pill of claim 11.

14. having a density of about 0.7 to 1.4 g / cc; The carbon pill of claim 11.

15. having a conductivity of about 16 to 140 mS / m; The carbon pill of claim 11.

16. further comprising a lubricious additive material to aid in the flow and compression of the first carbon material; The lubricity additive comprises at least one of the group consisting of microcrystalline cellulose, dicalcium phosphate, magnesium stearate, and silicon dioxide. The carbon pill of claim 11.

17. At least one end surface of the carbon pill is mainly flat or at least one end surface of the carbon pill belongs to the group of concave and convex surfaces. The carbon pill of claim 11.

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