Device and method for exfoliating graphite

Abstract

The invention discloses a device and method for exfoliating graphite particles. A mixture of graphite particles and a fluid medium is conveyed into a container. The container includes a stirrer and a cooler. The cooler cools the mixture so that the fluid medium at least partially solidifies into ice particles. The stirrer stirs the mixture to cause contact between the graphite particles and the ice particles. The contact between the graphite particles and the ice particles causes the graphite particles to be exfoliated.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 184,176, filed on May 4, 2021, under 35 U.S.C. §119(e), the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present invention generally relates to an apparatus and method for exfoliating graphite, and in particular, to an apparatus and method for exfoliating graphite particles using a fluid medium to produce graphene. Background Art

[0004] Graphene has been a highly sought-after commodity since its isolation in 2004. Composed of a single layer of carbon atoms, this material has been theorized and demonstrated to have remarkable properties, including high tensile strength, high flexibility, high thermal conductivity, and extremely high electrical conductivity. With more research and development each year, applications for this material abound.

[0005] However, the demand for graphene far outstrips the production capabilities of existing technologies. The first technique for producing graphene, informally known as the "scotch tape method," involves placing a strip of tape on the surface of a block of graphite, which is then peeled off to mechanically exfoliate graphite flakes, and then placing a second strip of tape, which is on top of the first, which is then peeled off to exfoliate even thinner graphite flakes; this process is repeated until the exfoliated single-layer graphene flakes end up on a strip of tape. Although single-layer graphene can be produced, the technique is labor-intensive and time-consuming, and requires the consumption of large amounts of tape and solvents to remove the tape and separate the graphene flakes. Not only is the process tedious, time-consuming, and costly, it is also environmentally unfriendly due to the waste it produces.

[0006] Since the introduction of the "Scotch tape method", other techniques have been developed over the years, which fall into the broad categories of "bottom-up" and "top-down" methodologies. Bottom-up techniques, such as chemical vapor deposition, assemble graphene at the nanoscale directly from free carbon atoms. Bottom-up techniques are able to produce graphene sheets of configurable sizes, but are limited by the fact that they can only produce a single sheet of graphene at a time. Top-down techniques, such as the "Scotch tape method", rely on the fact that naturally occurring graphite already consists of stacked layers of graphene that are held together by weak van der Waals forces, and attempt to peel these layers apart in order to isolate the graphene. Van der Waals forces include attractive and repulsive forces between atoms, molecules, and surfaces, as well as other intermolecular forces.

[0007] However, conventional exfoliation techniques are also limited by their efficiency and the quality of their final products. As mentioned earlier, the "scotch tape method" requires too much labor and material consumption, which is not conducive to large-scale industrial production of graphene. Other techniques, such as chemical exfoliation and liquid phase shear mixing, may be suitable for industrial production, but the final products produced are either damaged by oxidation or are slow to produce, which drives up production costs.

[0008] High-energy technologies that can produce graphene at high rates and high quality include laser-induced graphene ("LIG") and flash Joule heating ("FJH"). These technologies allow the use of carbon-containing non-graphite-based materials, such as rubber or organic waste, and can produce graphene at higher rates than previously discussed technologies. However, these technologies are limited by the intrinsic safety risks and costs of high-energy systems.

[0009] Therefore, there is a high demand for new technologies for graphene production that are safe and scalable to industrial levels. In addition, because the current price of graphene is a limiting factor in the introduction of new products that exploit the many useful properties of this material, new technologies for inexpensive graphene production are needed. Summary of the invention

[0010] A simplified summary of various aspects of the present invention is given below in order to provide a basic understanding of these aspects. This summary is not an exhaustive overview of the content of the present invention. It is neither intended to identify the key or critical elements of the present invention, nor to describe any scope of a specific embodiment of the present invention or any scope of the claims. Its only purpose is to present some concepts of the present invention in a simplified form as a prelude to a more detailed description presented later.

[0011] In one aspect of the present invention, an apparatus and method for exfoliating graphite to produce graphene is provided. A mixture is conveyed into a container. The mixture includes graphite particles and a fluid medium. The container includes an agitator. The mixture may be stirred by the agitator so that the graphite particles come into contact with ice particles, thereby exfoliating the graphite particles.

[0012] In one embodiment, the mixture can be transported to a container. The mixture includes graphite particles and a fluid medium. The container includes an agitator and a cooler. The mixture is cooled by the cooler so that the fluid medium at least partially solidifies into ice particles. The mixture is stirred by the agitator to cause contact between the graphite particles and the ice particles, thereby exfoliating the graphite particles.

[0013] In one embodiment, an apparatus for exfoliating graphite particles includes a container to hold a mixture. The container includes a cooler and an agitator. The mixture includes graphite particles and a fluid medium. The cooler is configured to cool the mixture to at least partially solidify the fluid medium into ice particles. The agitator is configured to stir the mixture to cause contact between the graphite particles and the ice particles, thereby exfoliating the graphite particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is illustrated by way of example and not by way of limitation in the accompanying drawings, in which:

[0015] Figure 1 illustratively depicting a series of contacts on a molecular scale between graphite particles and a fluid medium according to an embodiment of the present invention;

[0016] Figure 2 illustratively depicting an apparatus for exfoliating graphite in accordance with an embodiment of the present invention;

[0017] Figure 3 An apparatus for exfoliating graphite according to an embodiment of the present invention is schematically depicted;

[0018] Figure 4 illustratively depicting an apparatus for exfoliating graphite in accordance with an embodiment of the present invention; and

[0019] Figure 5 is a flow chart illustrating a method for exfoliating graphite according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] Before describing this subject in detail, it should be understood that the present invention is not limited to the specific embodiments described, as these may vary. It should also be understood that the terms used herein are only used to describe specific embodiments and are not intended to be limiting, as the scope of the present invention will be limited only by the appended claims. Although the present invention is susceptible to different forms of different embodiments, the preferred embodiments of the present invention are shown in the accompanying drawings and will be described in detail herein, and it should be understood that the present invention should be considered as an example of the principles of the present invention. It is disclosed and is not intended to limit the broad aspects of the disclosure to the embodiments shown. Unless otherwise stated, all features, elements, components, functions, and steps described with respect to any embodiment provided herein are intended to be freely combined and replaced with those from any other embodiment. Therefore, it should be understood that the content shown is set forth only for the purpose of example and should not be considered as limiting the scope of the present invention.

[0021] As used herein, "fluid" refers to a continuous, amorphous substance whose molecules move freely past each other and tend to take the shape of the container. Fluids include liquids and gases. Fluids may flow under certain conditions, such as when exposed to pressure or gravity.

[0022] As used herein, "grain" refers to a particle of a solid material whose components (e.g., atoms, molecules, or ions) are arranged in a highly ordered microstructure to form a lattice extending in all directions. Grains may include crystallographic defects such as vacancies, dislocations, impurities, and interstitial additions.

[0023] As used herein, "exfoliation" refers to the action of splitting particles of a layered material. The layered material may include any number of layers prior to exfoliation. During exfoliation, a grain is separated into a first new grain and a second new grain, the number of layers prior to exfoliation being the first new grain and the second new grain. The exfoliation action may continue on the first new grain and / or the second new grain to produce additional new grains.

[0024] As used herein, "graphene" refers to a monolayer ("monolayer") of carbon atoms, arranged in a hexagonal bond pattern. As used herein, "multilayer graphene" refers to a structure consisting of 2 to 10 layers of graphene, which are stacked on each other and held together by van der Waals forces. As used herein, "nanographite" refers to a structure consisting of 10 to 1000 layers of graphene, which are stacked on each other and held together by van der Waals forces. As used herein, "graphite" refers to a structure consisting of more than 1000 layers of graphene, which are stacked on each other and held together by van der Waals forces. However, any one of these terms can be used interchangeably, and without departing from the spirit and scope of the present invention, a method for producing a specific graphene layer can also produce other graphene layers.

[0025] As mentioned above, graphene is a very popular material with attractive properties. For example, graphene flakes can be used as an additive to other materials to increase their bending or compressive strength. In addition, its electrical conductivity is being studied for use in supercapacitors and as a replacement for copper in certain applications. Preliminary studies have shown that graphene can also be used as a filter in desalination systems with fascinatingly low energy consumption.

[0026] However, existing methods for producing graphene are limited by factors such as low productivity and high and expensive requirements for labor and / or materials. Existing methods that have successfully overcome production and scalability challenges also face other challenges. Because graphene's most attractive feature is its repeating hexagonal pattern of carbon atoms, the presence of defects can affect its usefulness. For example, when the structure of carbon atoms is damaged by oxidation, the benefits of graphene are reduced. Although graphene oxide can be reduced to form reduced graphene oxide, the defects contained in the final product can also reduce its efficacy. In addition, some suppliers advertise methods for producing single-layer graphene, but actually produce multi-layer graphene or even nanographite, which have only a small fraction of the beneficial effects of graphene. For example, the strength and conductivity of graphene are reduced by the presence of additional layers.

[0027] The present invention addresses the challenges faced by existing solutions by introducing a method and apparatus for exfoliating graphite to produce graphene that is highly scalable, requires low-cost labor and materials, can produce high-quality finished products, and presents minimal safety risks.

[0028] As described herein, the adhesive properties of a crystal structure can be used to clamp and mechanically exfoliate graphite layers to produce one or more layers of graphene. For example, ice can be used as the crystal structure. Water ice is a well-studied substance with mature regulatory and risk data. The temperatures and pressures at which ice forms can be achieved with minimal energy consumption and minimal risk to personnel and the environment. The labor, materials, and equipment required for this solution are inexpensive and can be easily scaled up to mass industrial production and sold at a cost-effective price.

[0029] In the following description and drawings, similar elements are identified with similar reference numerals. Unless otherwise indicated, the use of "such as", "etc", "or" and "similar" means unrestricted, non-exclusive alternatives. The use of "having", "including", "including" or "comprising" means "including but not limited to" or "including but not limited to".

[0030] Multiple entities listed with "and / or" should be interpreted in the same manner, i.e., "one or more" of the entities so connected. In addition to the entities specifically identified by the "and / or" clause, other entities may optionally be present, whether or not related to those specifically identified entities. Thus, as a non-limiting example, when used in conjunction with open language such as "including", a reference to "A and / or B" may refer in one implementation to only A (optionally including entities other than B); in another implementation to only B (optionally including entities other than A); and in another implementation to both A and B (optionally including other entities). These entities may refer to elements, actions, structures, steps, operations, values, etc.

[0031] Various aspects of the above-referenced systems are described in detail herein by way of example and not by way of limitation.

[0032] Figure 1 A series of contacts 100 of graphite particles 102 and fluid medium 104 on a molecular scale are illustratively depicted. Figure 1 The series of four steps (steps AD) for exfoliating graphite particles are described in detail. The series of contacts 100 includes a crystal structure layer 106, a crystal structure 108, and exfoliated graphite particles 110. Figure 1 A two-dimensional side view is depicted, with individual atoms depicted as circles and bonds between atoms depicted as lines. For simplicity and brevity, Figure 1 A graphite particle 102 comprising multilayer graphene is depicted, wherein five perpendicular graphene layers are stacked adjacent to one another and held together by van der Waals forces. As described above, each graphene layer comprises carbon atoms arranged in a hexagonal bond pattern. It should be noted that the process described below is expected to have a similar response regardless of the number of layers in the graphite particle 102. Thus, more or fewer layers than described may be used. Furthermore, for simplicity and brevity, although the Figure 1 One graphite particle 102 is depicted, but additional graphite particles may interact with the fluid medium 104.

[0033] In step A, graphite particles 102 are suspended as solid particles in a fluid medium 104. Figure 1 As shown, the fluid medium 104 may include multiple components (e.g., atoms, ions, or molecules). In one embodiment, the fluid medium 104 may be a solution including water. In another embodiment, the fluid medium 104 may be an aqueous solution containing water buffered by a buffer, such as acetic acid, citric acid, formic acid, borate, or potassium dihydrogen phosphate. In a third embodiment, the fluid medium 104 may include abrasive materials, such as silicon dioxide, calcite, or diamond powder. The fluid medium 104 may include a surfactant (e.g., soap, alkyl sulfate, alkyl benzene sulfonate, lignin sulfonate, n-methyl-2-pyrrolidone, sodium cholate, etc.) to change the characteristics of the fluid medium 104. The fluid medium 104 may also include a pour point depressant (e.g., ethylene glycol, methanol, propanol, or derivatives thereof, ethanol, sugar, etc.) to reduce the freezing temperature of the fluid medium 104. In other embodiments, the fluid medium 104 may be other fluids, other fluid solutions, or other solutions existing in other states.

[0034] After step A, Figure 1In step B, a heat sink such as a cooling plate (not depicted) is used to cool the fluid medium 104 to or below the freezing point freezing temperature. As used herein, "freezing temperature" refers to the temperature at which a material can begin to change thermodynamic phase from liquid to solid. The process of changing thermodynamic phase from liquid to solid is also referred to as "solidification". In a process called "nucleation", a liquid that solidifies into a crystalline structure may preferentially solidify onto other solids. The solid where the crystalline structure may begin to solidify is called a "nucleation site". In the present invention, as the fluid medium 104 solidifies, two or more of the molecules of the fluid medium 104 bond to each other in a repeating pattern to form a crystalline structure layer 106.

[0035] In one embodiment, the solidification temperature is the solidification temperature of pure water, which is approximately 0 degrees Celsius at one atmosphere. In response to cooling at or below the solidification temperature, the fluid medium 104 begins to solidify into a crystalline structure layer 106. The fluid medium 104 may solidify into the crystalline structure layer 106 at the nucleation sites. The graphite particles 102 may serve as nucleation sites for the crystalline structure layer 106. In one embodiment, as the fluid medium 104 solidifies, the fluid medium 104 may be selected so that the crystalline structure layer 106 adheres to the outer layer of the graphite particles 102.

[0036] After step B, Figure 1 In step C, the heat sink (not depicted) continues to cool the fluid medium 104 below the solidification point to remove latent heat and cause additional solidification of the fluid medium 104. In response to continued cooling, the fluid medium 104 continues to solidify, and the crystal structure layer 106 grows to form a crystal structure 108. In one embodiment, the crystal structure 108 may continue to grow (e.g., become larger and the fluid medium 104 molecules continue to combine with other molecules) until the fluid medium 104 is completely solidified or the heat sink (not depicted) stops cooling the fluid medium 104. The heat sink (not depicted) may stop cooling the fluid medium 104 in response to a user command, in response to an automatic command, or in response to a power outage.

[0037] After step C, in step D, the device (i.e., agitator) (not depicted) for generating agitation continues to agitate the graphite particles 102, the crystal structure 108, and the fluid medium 104. As used herein, "agitation" refers to increasing the kinetic energy of a substance. For example, a rotating blade or a vibration source can be used to agitate a substance by introducing kinetic energy. In one embodiment, the continued growth of the crystal structure 108 can increase the force caused by the resistance to motion (also referred to as "fluid resistance") within the fluid between the crystal structure 108 and the fluid medium 104. As the fluid resistance increases, the force is transmitted from the crystal structure 108 to the graphite particles 102. Ultimately, the tension transmitted to the graphite particles 102 may exceed the van der Waals forces (also referred to as "interlayer bonding strength") that hold the graphite layers together. Therefore, the interlayer bonding force can be overcome, and the crystal structure 108 can therefore be mechanically separated from the graphite particles 102.

[0038] In one embodiment, the fluid medium 104 is selected such that the bonding strength of the crystal structure 108 is greater than the interlayer bonding strength of the graphite particles 102. Therefore, the outer layer of the graphite particles 102 with the crystal structure 108 adhered thereto can be peeled off from the graphite particles with the crystal structure 108 adhered thereto. After the peeling, the peeled graphite particles 110 are separated from the graphite particles 102.

[0039] In one embodiment, the newly exposed outer layer of the exfoliated graphite particle 110 can then act as a nucleation site at which the particle begins to solidify to continue developing the crystalline structure layer 106 and the crystalline structure 108. Figure 1 Steps A to D in can be repeated on the exfoliated graphite particles 110 to further exfoliate the graphite. By repeating steps A to D (i.e., performing steps A to D and repeating these steps again and again), a series of contacts 100 as described above can reduce graphite to nanographite, multilayer graphene, and ultimately to graphene. In one embodiment, graphite is exfoliated into multilayer graphene within two hours of repeating steps A to D. In other embodiments, graphite can be exfoliated into graphene within any other time frame. Additional details about several embodiments are provided below, whereby the above-described technology can be implemented in a scalable and cost-effective manner.

[0040] Figure 2 An apparatus 200 for exfoliating graphite is illustratively depicted. The apparatus 200 for exfoliating graphite includes a container 202, an agitator 216, and a heat sink 218. The container 202 includes or otherwise contains a fluid medium 226 and at least graphite particles 228. The agitator 216 includes a motor 212, an input shaft 210, a gearbox 208, and an output shaft 206. The heat sink 218 includes a coolant inlet 220, a coolant outlet 222, and a cooler 224. The motor 212 includes a support arm 204 and a motor electrical input 214. The cooler 224 includes a cooler electrical input 230.

[0041] Container 202 may be constructed or otherwise manufactured to hold any volume of fluid medium determined by the designer of device 200. In one embodiment, container 202 is constructed of one or more of the following materials or a combination thereof: metal, plastic or polymer, or glass. Container 202 may be constructed of materials such as fiberglass, cotton, or Insulation materials such as Aerogel is a cryogenic insulation material to reduce unwanted heat transfer.

[0042] Graphite particles 228 and fluid medium 226 can be transported to container 202 to form a mixture. The mixture can contain graphite particles 228 and fluid medium 226 in any proportion. The volume of fluid medium 226 can be any volume that container 202 can accommodate, and the size of container 202 can vary. Fluid medium 226 can be any fluid, non-fluid or a combination thereof. In response to cooling below the freezing point, fluid medium 226 can at least partially solidify into a crystalline structure. In an embodiment, fluid medium 226 is deionized water, which at least meets the minimum purity standard of American Society for Testing and Materials (ASTM) type IV as described in ASTM D1193-91. In another embodiment, fluid medium 226 is a solution comprising water and at least one solute such as chloride, fluoride or one or more minerals. As used herein, "solute" refers to a minor component in a solution dissolved in a solvent. In a third embodiment, fluid medium 226 is another liquid. In other embodiments, fluid medium 226 can be a combination of non-fluid or fluid and non-fluid medium.

[0043] Graphite particles 228 may be added to container 202 before, simultaneously with, or after adding fluid medium 226. In one embodiment, graphite particles 228 may be cooled 202 before being introduced into container. In another embodiment, the temperature of graphite particles 228 may be equal to ambient temperature, such as 25 degrees Celsius or another temperature. Graphite particles 228 may be in the form of a powder (e.g., a powdered solid form) with an average flake size. In one embodiment, graphite particles 228 have an average flake size between 5 microns and 100 microns. In another embodiment, graphite particles 228 have an average flake size greater than 100 microns. In a third embodiment, graphite particles 228 are heterogeneous multiple graphite particles of any size that container 202 can accommodate.

[0044] The agitator 216 may be at least temporarily fixed, permanently fixed, or removably fixed to the container 202. In one embodiment, the agitator 216 includes one or more rotors that contact the fluid medium 226 to increase agitation and are at least occasionally in contact with the graphite particles 228. The rotor may include one or more blades extending outwardly from the shaft so that as the shaft rotates, the blades move through the fluid medium 226. The movement of the one or more blades may increase the kinetic energy of the fluid medium 226 to cause agitation. By rotating, the agitator 216 may initiate agitation in the fluid medium 226 and occasionally contact the graphite particles 228, causing the graphite particles 228 to move relative to the fluid medium 226.

[0045] "Circular rotation" as used herein refers to the periodic motion of one or more objects along a circle or the rotation along a circular path. The circular rotation may be uniform (e.g., with a constant rotational angular rate and a constant speed) or non-uniform with a variable rotational rate or a variable speed. In one embodiment, the circular rotation is generated by the motion of the motor 212. The motor 212 may be driven by a chemical fuel such as gasoline, liquefied petroleum gas (LPG) (i.e., propane) or diesel fuel or otherwise powered. Optionally, the motor 212 may be an electric motor driven by a motor electrical input 214, which may be coupled to a wired power supply and / or a battery. In one embodiment, the motor 212 is an alternating current ("A / C") motor. The motor 212 may be structurally supported by the support arm 204. The support arm 204 may be made of any type of material that may support the motor 212. The support arm 204 may be made of metal, plastic, rubber, cardboard, or a combination thereof.

[0046] One end of the input shaft 210 may be at least temporarily connected, permanently connected, or removably connected to the motor 212. The input shaft 210 may be welded, connected by a temporary or permanent joint, or otherwise connected to the motor 212. The input shaft 210 may be made of any kind of material capable of laterally supporting the motor 212. The input shaft 210 may be made of metal, plastic, rubber cardboard, or a combination thereof. In one embodiment, the opposite end of the input shaft 210 is at least temporarily connected, permanently connected, or removably connected to the gearbox 208. The input shaft 210 may be welded, connected by a temporary or permanent joint, or otherwise connected to the gearbox 208. The gearbox 208 may include two or more gears (not depicted). Each gear (not depicted) in the gearbox 208 may have a specific number of teeth. The rotation of a gear may be interlocked with one or more other gears, so that the rotation of one gear transmits force through the teeth to generate the rotation of one or more other gears. The ratio of the number of teeth between one gear and another gear is called a "gear ratio". The total gear ratio of all interlocking gears in the gearbox 208 is referred to as the "gear ratio" of the gearbox 208. The gearbox 208 operates to mechanically convert the rotation of the input shaft 210 into a second rotation such that the rate of the second rotation is different from the rate of rotation of the input shaft 210 according to the gear ratio. In one embodiment, the gearbox 208 can mechanically convert the rotation of the input shaft 210 into the second rotation such that the direction of the second rotation is different from the direction of rotation of the input shaft 210 according to the angle. The gearbox 208 can be at least temporarily connected, permanently connected, or removably connected to the output shaft 206. The output shaft 206 can be welded, connected by a temporary or permanent joint, or otherwise connected to the gearbox 208.

[0047] In an alternative embodiment (not depicted), the motor 212 may be at least temporarily coupled, permanently coupled, or removably coupled directly to the output shaft 206 without an input shaft. In such an embodiment, the rate of rotation of the motor 212 is the same or substantially the same (e.g., within + / - 5%) as the rate of rotation of the output shaft 206, and the direction of rotation of the motor 212 is the same or substantially the same (e.g., within + / - 5%) as the direction of rotation of the output shaft 206.

[0048] In one embodiment, the rate of rotation of the output shaft 206 can affect the degree of agitation produced by the agitator 216. In one embodiment, one or more rotors are connected to the output shaft 206 to provide additional agitation. The rotor may include one or more blades extending outwardly from the shaft so that as the shaft rotates, the blades move through the fluid medium 226. The movement of the one or more blades can increase the kinetic energy of the fluid medium 226 to produce agitation. The degree of agitation produced by the agitator 216 can be such that when a crystal structure forms in the fluid medium 226 in response to cooling, the agitation produces a shear force applied to the crystal structure sufficient to overcome the internal bonding strength of the graphite particles 228, as described above. Figure 1 shown.

[0049] In one embodiment, the fluid medium 226 is configured such that in response to being cooled to a temperature below the freezing point of the fluid medium 226, the fluid medium 226 at least partially solidifies into a crystalline structure and adheres to the outer layer of graphite particles 228. The heat sink 218 is capable of cooling the fluid medium 226 and the graphite particles 228 to below the solidification temperature of the fluid medium 226.

[0050] A portion of the heat sink 218 can be secured to the bottom of the container 202. The container 202 can transfer heat to the heat sink 218. The heat can be by conduction, convection, radiation, or a combination thereof. The portion of the heat sink 218 secured to the bottom of the container 202 can include channels (not shown) that allow a liquid coolant to flow through. In one embodiment, the liquid coolant is one of sodium chloride, ethylene glycol, isopropanol, methanol, butanol, ethanol, liquid nitrogen, or another liquid or combination of liquids.

[0051] The heat sink 218 may include a coolant inlet 220 and a coolant outlet 222 that are at least temporarily connected, permanently connected, or removably connected at one end to a portion of the heat sink 218 that is fixed to the bottom of the container 202. In one embodiment, the coolant inlet 220 and the coolant outlet 222 include pipes that allow liquid coolant to flow. The pipes may be made of metal, plastic, rubber, cardboard, or a combination thereof. The coolant inlet 220 and the coolant outlet 222 may be insulated using an insulating material such as fiberglass, cotton, or Cryogel, It is an aerogel cryogenic insulation material to reduce heat transfer in and out of the coolant inlet 220 or the coolant outlet 222.

[0052] The coolant inlet 220 and the coolant outlet 222 can be at least temporarily connected, permanently connected, or removably connected to a cooler 224 at the other end. The cooler 224 is made of metal, plastic, rubber, cardboard, or a combination thereof. In one embodiment, the cooler 224 is capable of cooling the liquid coolant away from the device 200 in the coolant outlet 222 and returning the liquid coolant at a lower temperature in the coolant inlet 220. The cooler 224 can be a tank containing a cryogenic fluid, such as liquid nitrogen. In an alternative embodiment, the cooler 224 is an electrical device for cooling a fluid, having a cooler electrical input 230. The cooler 224 can cool the liquid coolant at a constant (same) rate. In an embodiment, the cooler 224 can alternatively cool the liquid coolant at a variable rate.

[0053] By cooling the liquid coolant, the heat sink 218 can cool the fluid medium 226 and the graphite particles 228 to below the solidification temperature of the fluid medium 226. Thus, through a combination of cooling and stirring, the apparatus 200 causes the formation and exfoliation of the crystalline structure in the fluid medium 226, as well as the exfoliation of the graphite particles 228. However, as discussed herein, other apparatuses may be employed to achieve similar or identical effects in a scalable and cost-effective manner.

[0054] Figure 3 An apparatus 300 for exfoliating graphite is illustratively depicted. The components in the apparatus 300 may be similar or identical to the components in the apparatus 200, and thus, the description of the components in the apparatus 200 also applies to the components in the apparatus 300. The apparatus 300 for exfoliating graphite includes a container 302, an agitator 304, and a heat sink 308. The container 302 includes a fluid medium 312 and graphite particles 310. The agitator 304 includes an agitator electrical input 306.

[0055] The container 302 can be created or otherwise manufactured to hold any volume of fluid medium 312 determined by the designer of the device 300. In one embodiment, the container 302 is constructed of one or more of metal, plastic or polymer, or glass. The container 302 can be insulated to reduce unwanted heat transfer.

[0056] Graphite particles 310 and fluid medium 312 can be transported to container 302 to form a mixture. The volume of fluid medium 312 can be any volume that container 302 can accommodate, and the size of container 302 can vary. Fluid medium 312 can be any fluid, wherein fluid medium 312 is at least partially solidified into a crystalline structure (not shown) in response to cooling below the freezing point. In one embodiment, fluid medium 312 is deionized water that meets minimum purity standards. In another embodiment, fluid medium 312 is a solution comprising water and at least one solute. "Solute" as used in this application refers to a minor component dissolved in a solvent in a solution. In a third embodiment, fluid medium 312 is another liquid.

[0057] The graphite particles 310 may be added to the container 302 before or after the addition of the fluid medium 312. The graphite particles 310 may be cooled before being introduced into the container 302. The graphite particles 310 may be in the form of a powder having an average flake size. In one embodiment, the graphite particles 310 have an average flake size between 5 microns and 100 microns. In another embodiment, the graphite particles 310 have an average flake size greater than 100 microns. In a third embodiment, the graphite particles 310 are a heterogeneous plurality of graphite particles of any size that the container 302 can accommodate.

[0058] The agitator 304 is at least temporarily, removably, or permanently affixed to the container 302. In one embodiment, the agitator 304 includes one or more vibrators (305) in contact with an outer surface of the container 302. By vibrating, the agitator 304 can initiate agitation in the fluid medium 312, causing the graphite particles 310 to move relative to the fluid medium 312.

[0059] The vibration frequency and amplitude of the stirrer 304 affect the degree of agitation produced by the stirrer 304. In one embodiment, the stirrer 304 is capable of producing a vibration frequency greater than 40 kHz. The degree of agitation produced by the stirrer 304 can be configured such that when a crystalline structure is formed in the fluid medium 312 in response to cooling, the agitation is sufficient to overcome the internal bonding strength of the graphite particles 310, as described above. Figure 1 shown.

[0060] In one embodiment, the fluid medium 312 is configured so that in response to being cooled below the solidification temperature, the fluid medium 312 at least partially solidifies into a crystalline structure and adheres to the outer layer of the graphite particles 310. The "solidification temperature" used in this application refers to the temperature at which a material can begin to change the thermodynamic phase from a liquid to a solid. The process of changing the thermodynamic phase from a liquid to a solid is also called "solidification". In a process called "nucleation", a liquid that solidifies into a crystalline structure may preferentially solidify onto other solids. The solid where the crystalline structure may begin to solidify is called a "nucleation site". In the present invention, as the fluid medium 312 solidifies, two or more of the molecules of the fluid medium 312 bond to each other in a repeating pattern to form a crystalline structure layer (not depicted). The heat sink 308 is capable of cooling the fluid medium 312 and the graphite particles 310 below the solidification point. In one embodiment, the solidification temperature is the freezing point of pure water, which is about 0 degrees Celsius at one atmosphere.

[0061] The heat sink 308 can be a substance whose instantaneous temperature is low enough to cool the fluid medium 312 below the freezing point. In one embodiment, the heat sink 308 is added to the fluid medium 312 after the fluid medium 312 and the graphite particles 310 are introduced into the container 302. The heat sink 308 can be a solid substance or a liquid substance. In one embodiment, the heat sink 308 is a certain volume of solid carbon dioxide, also known as dry ice. In another embodiment, the heat sink 308 is a certain volume of cryogenic liquid, such as liquid nitrogen, liquid oxygen, or liquid helium.

[0062] By simple heat transfer, the heat sink 308 can cool the fluid medium 312 and the graphite particles 310 to below the freezing point. Thus, through a combination of cooling and agitation, the device 300 causes the formation and disruption of the crystalline structure in the fluid medium 312, as well as the exfoliation of the graphite particles 310. However, as will be discussed below, other devices may also be used to achieve the same effect in a scalable and cost-effective manner.

[0063] Figure 4 An apparatus 400 for exfoliating graphite is illustratively depicted. The components in apparatus 400 may be similar or identical to the components in apparatus 200 and apparatus 300, and thus, the description of the components in apparatus 200 and apparatus 300 also applies to the components in apparatus 400. Apparatus 400 for exfoliating graphite includes a container 422, an agitator 402, a heat sink 406, and a graphite block 408. Container 422 includes a fluid medium 418 and graphite particles 420. Agitator 402 includes an agitator electrical input 404. Heat sink 406 includes a coolant inlet 410, a coolant outlet 412, and a cooler 414. Cooler 414 includes a cooler electrical input 416.

[0064] The container 422 forms the core of the device 400. The container 422 can be constructed or otherwise manufactured to hold any volume of the fluid medium 418 determined by the designer of the device 400. In one embodiment, the container 422 is formed of one or more metals, plastics or polymers, or glass. The container 422 can be made of materials such as fiberglass, cotton, or Insulation materials for insulation, The aerogel low temperature insulation material is used to reduce the heat transferred from the container 422.

[0065] Graphite particles 420 and fluid medium 418 can be transported to container 422 to form a mixture. The volume of fluid medium 418 can be any volume that container 422 can accommodate. Fluid medium 418 can be any fluid, wherein fluid medium 418 responds to cooling below the freezing point and at least partially solidifies into a crystalline structure (not shown). In one embodiment, fluid medium 418 is deionized water that meets minimum purity standards. In another embodiment, fluid medium 418 is a solution comprising water and at least one solute. "Solute" as used in this application refers to a minor component in a solution that is dissolved in a solvent. In a third embodiment, fluid medium 418 is another liquid.

[0066] Graphite particles 420 may be added to container 422 before or after the addition of fluid medium 418. Graphite particles 420 may be cooled prior to introduction into container 422. Graphite particles 420 may be in the form of a powder having an average flake size. In one embodiment, graphite particles 420 have an average flake size between 5 microns and 100 microns. In another embodiment, graphite particles 420 have an average flake size greater than 100 microns. In a third embodiment, graphite particles 420 are heterogeneous diversified graphite particles of any size that container 422 can accommodate.

[0067] The agitator 402 is at least temporarily fixed, removably fixed, or permanently fixed to the heat sink 406. In one embodiment, the agitator 402 includes one or more vibration units in contact with the top of the heat sink 406. By vibrating, the agitator 402 can initiate agitation in the fluid medium 418, causing the graphite particles 420 to move relative to the fluid medium 418.

[0068] The vibration frequency and amplitude of the agitator 402 affect the degree of agitation produced by the agitator 402. In one embodiment, the agitator 402 is capable of producing a vibration frequency greater than 40 kHz. The degree of agitation produced by the agitator 402 can be sufficient to overcome the internal bonding strength of the graphite particles 420 when a crystalline structure forms in the fluid medium 418 in response to cooling.

[0069] In one embodiment, in response to being cooled below the freezing point, the fluid medium 418 at least partially solidifies into a crystalline structure such as ice particles and may adhere to the outer layer 420 of the graphite particles. The thermal energy sink 406 can cool the fluid medium 418 and the graphite particles 420 below the freezing point.

[0070] A portion of the heat sink 406 may be fixed to the bottom of the stirrer 402. The stirrer 402 may conduct heat to the heat sink 406. The portion of the heat sink 406 fixed to the bottom of the stirrer 402 may include a channel (not shown) to allow a liquid coolant to flow. In one embodiment, the liquid coolant is one of ethylene glycol, isopropanol, methanol, butanol, liquid nitrogen, or other liquids.

[0071] The heat sink 406 may include a coolant inlet 410 and a coolant outlet 412, which are at least temporarily connected, removably connected, or permanently connected at one end to a portion of the heat sink 406 fixed to the bottom of the agitator 402. In a specific implementation, the coolant inlet 410 and the coolant outlet 412 are pipes that allow liquid coolant to flow. The coolant inlet 410 and the coolant outlet 412 can be insulated to reduce unwanted heat transfer.

[0072] The coolant inlet 410 and the coolant outlet 412 may be at least temporarily connected, removably connected, or permanently connected to a cooler 414 at the other end. In one embodiment, the cooler 414 is capable of cooling the liquid coolant in the coolant outlet 412 away from the device 400 and returning the liquid coolant at a lower temperature in the coolant inlet 410. In one embodiment, the cooler 414 is capable of returning the liquid coolant at a temperature below -20 degrees Celsius in the coolant inlet 410. The cooler 414 may be a tank containing a cryogenic material such as liquid nitrogen, liquid hydrogen, liquid oxygen, or liquid helium. Alternatively, the cooler 414 may be a hopper containing solid carbon dioxide (also known as dry ice). In other embodiments, the cooler 414 may be any other mechanism that can cool the liquid coolant. In one embodiment, the cooler 414 is an electrical device for cooling a fluid, having a cooler electrical input 416. The cooler 414 may cool the liquid coolant at a constant rate. In an embodiment, the cooler 414 may alternatively cool the liquid coolant at a variable rate.

[0073] In one embodiment, the coolant outlet 412 can be directed to a vent (not shown). In this embodiment, the cooler 414 supplies cooling gas to the coolant inlet 410. The cooling gas can pass through the fluid medium 418 as a plurality of bubbles to cool the fluid medium 418 by conduction. In one embodiment, the plurality of bubbles can act as nucleation sites, as described above, for forming a crystalline structure. The cooling gas may include at least one of air, helium, nitrogen, neon, argon or carbon dioxide. The coolant outlet 412 may also be at least partially directed to a gas recovery system (not shown).

[0074] The graphite block 408 may be at least temporarily affixed, removably affixed, or permanently affixed to the bottom of the heat sink 406. In one embodiment, the graphite block 408 is maintained at least partially in liquid contact with the surface of the fluid medium 418. Since graphite is a thermal conductor, the graphite block 408 may be used to transfer heat from the fluid medium 418 to the heat sink 406. When the fluid medium 418 cools below the freezing point, crystalline structures such as ice particles may form on the surface of the graphite block 408. The agitation generated by the agitator 402 may be sufficient to overcome the interlayer bonding strength in the graphite block 408, causing the crystalline structure to be mechanically separated from the graphite block 408. Therefore, the graphite block 408 may be at least a partial source of graphite particles 420.

[0075] By cooling the liquid coolant, the heat sink 406 can cool the graphite block 408, the fluid medium 418, and the graphite particles 420 to below the freezing point. Thus, through a combination of cooling and agitation, the device 400 causes the formation and disruption of the crystalline structure in the fluid medium 418, as well as the exfoliation of the graphite particles 420. Thus, as described above, several methods can be employed to achieve the same effect in a scalable and cost-effective manner.

[0076] The steps for exfoliating graphite are referred to below Figure 5 Give a description.

[0077] Figure 5 is a flow chart illustrating a method 500 for exfoliating graphite. In one embodiment, the method 500 may be performed using any of the apparatuses described herein for exfoliating graphite. Figure 2 , Figure 3 and Figure 4 The apparatus 200, the apparatus 300 and / or the apparatus 400 depicted in the figure may perform the steps of the method 500. In addition, the method 500 may also be performed by another apparatus for exfoliating graphite.

[0078] For simplicity of explanation, the method of the present invention is depicted and described as a series of actions. However, the behavior according to the present invention can occur in various orders and / or simultaneously, and occur with other behaviors not presented and described herein. In addition, not all illustrated actions need to implement the method according to the disclosed subject matter. In addition, those skilled in the art will understand and appreciate that the method can be represented as a series of interrelated states alternatively by state diagrams or events.

[0079] Reference Figure 5 , method 500 begins at block 502, where graphite particles and a fluid medium are delivered to a container. For example, graphite particles (228, 310, and / or 420) and a fluid medium (226, 312, and / or 418) are delivered to a container (202, 302, and / or 422). The container (202, 302, and / or 422) can receive and store any number of graphite particles (228, 310, and / or 420) and a fluid medium (226, 312, and / or 418) in proportion. The graphite particles (228, 310, and / or 420) and the fluid medium (226, 312, and / or 418) can be introduced into the container (202, 302, and / or 422) by a delivery system or by manual or other processes.

[0080] In block 504, the graphite particles and the fluid medium are stirred by the stirrer so that the graphite particles move relative to the fluid medium. For example, the stirrer (216, 304, and / or 402) stirs the graphite particles (228, 310, and / or 420) and the fluid medium (226, 312, and / or 418) so that the graphite particles (228, 310, and / or 420) move relative to the fluid medium (226, 312, and / or 418). The stirrer (216, 304, and / or 402) can move the graphite particles (228, 310, and / or 420) relative to the fluid medium (226, 312, and / or 418) at a stirring rate. In one embodiment, the stirring rate is constant (e.g., within + / - 5%) throughout the operating cycle. In another embodiment, two or more stirring rates or directions can be used during the operating cycle.

[0081] In block 506, a cooler cools the graphite particles and the fluid medium such that the fluid medium at least partially solidifies into ice particles. For example, the heat sink (218, 308, and / or 406) cools the graphite particles (228, 310, and / or 420) and the fluid medium (226, 312, and / or 418) to a temperature below the freezing point. In one embodiment, the fluid medium (226, 312, and / or 418) is configured such that the fluid medium (226, 312, and / or 418) at least partially solidifies into a crystalline structure (108), such as ice particles, in response to cooling to a temperature below the freezing temperature of the fluid medium (226, 312, and / or 418). In further embodiments, as the fluid medium (226, 312, and / or 418) solidifies into a crystalline structure (108), such as ice particles, the fluid medium can adhere to an outer layer of the graphite particles. In one embodiment, the crystal structure (108) is delivered to the container (202, 302, and / or 422) from an external source.

[0082] In block 508, the agitator agitates the graphite particles, the ice particles, and the fluid medium to induce contact between the graphite particles and the ice particles to exfoliate the graphite particles. For example, the agitator (216, 304, and / or 402) agitates the graphite particles (228, 310, and / or 420), the crystal structure (108), and the fluid medium (226, 312, and / or 418) together to induce contact between the graphite particles (228, 310, and / or 420) and the crystal structure (108) to exfoliate the graphite particles. In one embodiment, in block 508, the heat sink (218, 308, and / or 406) continues to cool the graphite particles (228, 310, and / or 420) and the fluid medium (226, 312, and / or 418) so that the size of the crystal structure (108) continues to grow, for example, from 5 microns in diameter to 10 microns. In response to the increased fluid resistance during agitation, forces are transmitted to the graphite particles (228, 310, and / or 420), thereby overcoming the interlayer bonding van der Waals forces of the graphite particles.

[0083] The crystal structure (108) can be mechanically separated from the graphite particles (228, 310, and / or 420) by one of the following mechanical forces when the interlayer bonding strength of the graphite particles (228, 310, and / or 420) is overcome. The mechanical forces on the crystal structure (108) and the graphite particles (228, 310, and / or 420) can include any fluid friction, dynamic contact with an agitator, dynamic contact with another crystal structure (108), or dynamic contact with another graphite particle (228, 310, and / or 420). In one embodiment, the fluid medium (226, 312, and / or 418) is configured such that the bonding strength of the crystal structure is greater than the interlayer bonding strength of the graphite caused by van der Waals forces. Thus, mechanical separation of the crystal structure from the graphite grains (228, 310, and / or 420) is expected to break apart the graphite grains (228, 310, and / or 420), wherein at least one outer layer of the graphite particles (228, 310, and / or 420) remains adhered to the crystal structure. Thus, at least one outer layer of the graphite particles (228, 310, and / or 420) may be peeled from the crystal structure.

[0084] In one embodiment, the steps described in blocks 504 to 508 are repeated repeatedly during at least a portion of the operating cycle of the apparatus for exfoliating graphite. Thus, the outer layer of the graphite particles (228, 310, and / or 420) exposed by exfoliation can undergo further crystal structure adhesion and exfoliation. In one embodiment, the graphite particles (228, 310, and / or 420) can be reduced to nanographite, multilayer graphene, and ultimately to graphene. In one embodiment, the graphite particles (228, 310, and / or 420) are reduced to multilayer graphene within two hours.

[0085] In yet another embodiment, in order to exfoliate graphite particles, the following steps are taken: a mixture is delivered to a container; the mixture includes graphite particles and ice particles; the container includes a stirrer; the mixture is stirred by the stirrer to cause contact between the graphite particles and the ice particles to exfoliate the graphite particles.

[0086] In yet another embodiment, in order to exfoliate graphite particles, the following steps are taken: a mixture is transported into a container; the mixture includes graphite particles and a fluid medium; the container includes a stirrer and a cooler; the mixture is cooled by the cooler so that the fluid medium at least partially solidifies into ice particles; the mixture is stirred by the stirrer to cause contact between the graphite particles and the ice particles, thereby exfoliating the graphite particles.

[0087] In one embodiment, the agitator comprises a rotor. In one embodiment, the rotor comprises a first blade and a second blade.

[0088] In one embodiment, the agitator comprises a vibrator.

[0089] In one embodiment, the fluid medium comprises a first fluid, wherein the first fluid comprises water. The fluid medium also comprises a second fluid. The second fluid comprises at least one of ethylene glycol, n-methyl-2-pyrrolidone, isopropanol, methanol, butanol or ethanol. In another embodiment, the second fluid comprises at least one of air, nitrogen, argon, oxygen or carbon dioxide.

[0090] In one embodiment, the fluid medium further comprises a surfactant, which comprises at least one of soap, alkyl sulfate, alkyl benzene sulfonate, lignin sulfonate or sodium cholate.

[0091] Although the embodiments are susceptible to various modifications and alternative forms, specific examples thereof have been shown in the drawings and described in detail herein. However, it should be understood that these embodiments are not limited to the specific forms disclosed, but rather, these embodiments will cover all modifications, equivalents, and alternatives that fall within the spirit of the invention. In addition, any features, functions, steps, or elements of the embodiments may be recorded in or added to the claims, as well as the negative limitation of the scope of the invention of the claims by defining the features, functions, steps, or elements that do not belong to the claims.

Claims

1. A method for exfoliating graphite particles, the method comprising: Transfer the mixture into a container, wherein the mixture comprises the graphite particles and a fluid medium, and wherein the container comprises an agitator and a cooler; cooling the mixture by a cooler so that the fluid medium at least partially solidifies into ice particles; and Stirring the mixture with a stirrer to bring the graphite particles into contact with the ice particles, thereby exfoliating the graphite particles; Wherein, the fluid medium includes a first fluid, and the first fluid includes water.

2. The method of claim 1, wherein the agitator comprises a rotor.

3. The method of claim 1, wherein the agitator comprises a vibrator.

4. The method according to claim 1, characterized in that The fluid medium also includes a second fluid.

5. The method of claim 4, wherein the second fluid comprises at least one of ethylene glycol, n-methyl-2-pyrrolidone, isopropanol, methanol, butanol, and ethanol.

6. The method according to claim 4, characterized in that The second fluid includes at least one of air, nitrogen, argon, oxygen and carbon dioxide.

7. The method according to claim 1, characterized in that The fluid medium also includes a surfactant.

8. The method of claim 7, wherein the surfactant is soap.

9. The method according to claim 7, wherein the surfactant is at least one of alkyl sulfate, alkylbenzene sulfonate, lignin sulfonate and sodium cholate.

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