Cascade flash Joule heating method and system

Abstract

The invention provides a method of cascade flash (FWF) Joule heating and a system thereof. The FWF Joule heating process subjects an external feedstock in an external vessel to a flash Joule heating process, wherein the flash Joule heating process of the external feedstock causes conversion of an internal feedstock within an internal vessel (the internal vessel is within the external vessel) to a converted material.

Description

[0001] Cross-referencing of related patent applications

[0002] This application claims priority to U.S. Patent Application Serial No. 63 / 520,553, filed August 18, 2023, entitled “Methods of Flash-Within-Flash Joule Heating And Compositions Thereof,” which is jointly owned by the owners of this invention and whose entire contents are incorporated herein by reference. Technical Field

[0003] This invention relates to a method and system for flash Joule heating (FJH), specifically including a method and system for cascade flash Joule heating.

[0004] Government interests

[0005] This invention was completed with government support under grant number FA9550-22-1-0526 granted by the U.S. Air Force Office of Scientific Research and grant numbers ERDC W912HZ-21-2-0050 and W912HZ-24-2-0027 granted by the U.S. Army Corps of Engineers' Engineering Research and Development Center. The U.S. government holds certain rights to this invention. Background Technology

[0006] Next-generation synthetic methods must meet three main criteria to provide minimal environmental impact: reduced solvent and water use, improved energy efficiency, and scalability [Raabe 2023; Aykol 2021]. These requirements are often difficult to achieve using thermodynamic equilibrium states, as many synthetic processes require high temperatures (>600°C) or extended reaction times (ranging from hours to days). Recently, non-equilibrium synthesis using rapid thermal shock via ultrafast resistance Joule heating has emerged as a more promising approach for producing specific products, including ceramics [Wang C 2022; Deng II 2022], metastable materials [Zheng 2023; Chen II 2021], and value-added chemicals and materials [Luong 2020; Deng I 2022; Wyss 2022; Wyss 2023; Yao 2018; Chen 2016]. These established methods complete within milliseconds to minutes, demonstrating significant reductions in energy consumption. However, these methods typically require meeting specific conductivity requirements, which limits the reagents that can be used. To circumvent this limitation, conductive additives or substrates need to be introduced, which introduces impurities and makes it difficult to obtain a standalone product. Furthermore, the incorporation of volatile reagents such as chalcogens (e.g., S and Se) is difficult due to the intense heat generated by resistance heating, further limiting the incorporation of these elements.

[0007] A limitation of FJH is the difficulty in producing amorphous carbon as the primary product from a variety of carbon-based feedstocks, including municipal solid waste (<90%). Unlike disordered-layer graphene, amorphous carbon does not exhibit crystallinity and has wide applications in air and water filters, cosmetics, inks, and composite materials. The category of amorphous carbon encompasses materials such as (activated) charcoal, activated carbon, biochar, and combinations and mixtures thereof. Because FJH converts these carbon feedstocks into disordered-layer graphene during the reaction, it is difficult to obtain amorphous carbon materials and derivatives (e.g., heteroatom-doped amorphous carbon).

[0008] Therefore, conventional flash Joule heating (FJH) is generally unsuitable for the production of inorganic compounds. Instead, inorganic compounds are typically produced via methods such as chemical vapor deposition, flux growth, arc melting, and hydrothermal synthesis. These methods typically involve trade-offs between crystal quality, synthesis rate, and scalability. For example, chemical vapor deposition can produce high-quality crystalline materials, but it is difficult to produce gram-scale or larger crystals within one hour. Similarly, flux growth can produce high-quality gram-scale inorganic crystals, but for many compounds, synthesis times range from several hours to several weeks. Conventional flash Joule heating has been shown to enable reactions with high crystal quality at the gram level within seconds, but until now, it has been significantly limited in the variety of inorganic compounds it can be used to produce due to carbide formation, carbon contamination, and unsuitable resistivity. Summary of the Invention

[0009] This invention relates to a method and system for flash Joule heating, specifically including a method and system for cascade flash (FWF) Joule heating.

[0010] Generally, in one embodiment, the invention is characterized by a method comprising providing an internal feedstock within an inner container. The method further comprises providing an external feedstock within an outer container. The inner container is located within the outer container of a flash Joule heating apparatus. The method further comprises applying one or more voltage pulses, alternating current (AC), direct current (DC), or combinations thereof across the external feedstock to subject the external feedstock to a flash Joule heating process, wherein the flash Joule heating process of the external feedstock results in the internal feedstock being transformed into the transformed material.

[0011] Embodiments of the present invention may include one or more of the following features:

[0012] This method can be carried out in a continuous process, wherein voltage is supplied to the external raw material heated by flash joules.

[0013] The flash Joule heating process of external raw materials can provide conductive and / or radiative heating to internal raw materials, which causes the internal raw materials to be transformed into the transformed material.

[0014] The flash joule heating process of external raw materials can provide conductive heating to internal raw materials, which causes the internal raw materials to be transformed into the transformed material.

[0015] The flash joule heating process of external raw materials can provide radiant heating to internal raw materials, which causes the internal raw materials to be transformed into the transformed material.

[0016] The flash Joule heating process of external raw materials can provide both conductive and radiative heating to internal raw materials, resulting in the transformation of internal raw materials into transformed materials.

[0017] The transformed material can be a three-dimensional material.

[0018] The transformed material can be a two-dimensional material.

[0019] The transformed material can be a one-dimensional material.

[0020] The transformed material can be an amorphous material.

[0021] The transformed material can be selected from the following groups: FeS2, CoS2, CoS x Se y , CoSe, NiS2, NiSe2, Cu9S5, NbSe2, MoSe2, TiSe2, In2Se3, SnS2, SnS x Se y ,SnSe2,WSe2,WS2,Bi2S3,Bi x S y Se z ,Bi2Se3,TiN,LaBO3,Cu2Se,Cu 0.87 Se and its combinations and mixtures.

[0022] The converted materials may include chalcogenides, metals and / or alloys.

[0023] Reactors can be used to extract metals from ores and minerals.

[0024] The reactor can be used to extract metals from electronic waste sources.

[0025] The transformed materials may include amorphous carbon and its derivatives.

[0026] External raw materials can be selected from the following groups: graphene, flash graphene, disordered graphene, anthracite, coconut shell-derived carbon, high-temperature treated biochar, activated carbon, calcined petroleum coke, metallurgical coke, coke, sub-graphite, carbon nanotubes, asphaltene, acetylene black, carbon black, ash, carbon fiber, graphite and combinations and mixtures thereof.

[0027] By applying a voltage pulse across an external material to subject it to a flash Joule heating process, the external material can be converted into flash graphene.

[0028] Flash-evaporated graphene can be reused multiple times as an external raw material in the above methods.

[0029] The method may further include removing the converted material from the inner container. The method may further include providing a second internal feedstock within the inner container. The method may further include applying one or more voltage pulses, alternating current (AC), direct current (DC), or a combination thereof across the flash graphene in the outer container to subject the flash graphene to a flash Joule heating process, wherein the flash Joule heating process on the flash graphene causes the second internal feedstock to be converted into the second converted material.

[0030] The second internal raw material can be of the same type as the internal raw material that is transformed into the transformed material. The second transformed material can be of the same type as the transformed material.

[0031] The second internal raw material can be a different type of raw material from the internal raw material that has been transformed into the transformed material. The second transformed material can be a different type from the transformed material.

[0032] The step of applying one or more voltage pulses can utilize DC voltage.

[0033] The step of applying one or more voltage pulses can utilize pulsed DC.

[0034] The step of applying one or more voltage pulses can utilize AC voltage.

[0035] The step of applying one or more voltage pulses can utilize a combination of DC and AC voltages.

[0036] The step of applying one or more voltage pulses, AC, DC, or a combination thereof may include controlling the flash Joule heating process by controlled electronic modulation. Controlled electronic modulation can occur through control selected from variable frequency drive (VFD), pulse width modulation (PWM), proportional-integral-derivative (PID) control, three-term control, and combinations thereof.

[0037] Controlled electronic modulation can utilize (i) DC current; (ii) uniform, non-traveling AC current; or (iii) a combination thereof.

[0038] The method may further include applying an internal container current through the internal material when one or more voltage pulses, AC, DC or a combination thereof are applied across the external material.

[0039] When one or more voltage pulses, AC, DC, or a combination thereof are applied across the external material, the current applied through the internal material can be independently controlled.

[0040] Individual tubes can be made from graphite foil rolled into cylinders, which are used as heating elements outside the inner quartz tube.

[0041] Graphite tubes can be used as both heating tubes and material holding tubes.

[0042] A gap or physical separation may exist between the graphite tube and the inner tube to suppress conductive heating of the inner tube and promote radiation as the primary heating mechanism.

[0043] The entire system can be sealed with a quartz tube.

[0044] An inert gas can flow through the gap to allow for heating via convection, conduction, and / or a combination thereof.

[0045] Reactive gases can flow into the chamber along with the raw materials to assist in chemical synthesis or decomposition.

[0046] The reactive gas can be chlorine.

[0047] Reactive gases can flow into the chamber along with the raw materials to assist in the chemical synthesis or decomposition of the ore.

[0048] Individual tubes can be reused multiple times.

[0049] Individual tubes can be made of graphite. (Because graphite is stable when electrically heated, it can be reused multiple times.)

[0050] The system can be arranged in a concentric tube pattern, alternating between heating tubes and raw material holding tubes.

[0051] The tube can have a cylindrical shape.

[0052] The tube can have a non-cylindrical shape.

[0053] Non-cylindrical shapes can be semi-cylindrical.

[0054] Generally, in another embodiment, the invention is characterized by an apparatus comprising an inner container operable to receive an inner raw material. The apparatus further comprises an outer container operable to receive an outer raw material. The outer container is a conductive container operable to confine a non-conductive container containing the outer raw material or operable to directly flash Joule heating. The apparatus further comprises electrodes operable to apply voltage pulses, AC, DC, or combinations thereof across the outer raw material confined within the outer container to subject the outer raw material to a flash Joule heating process, wherein the flash Joule heating of the outer raw material results in the conversion of the inner raw material into the converted material.

[0055] Embodiments of the present invention may include one or more of the following features:

[0056] The outer container may be a non-conductive container that is operable to confine external materials.

[0057] The outer container can be a conductive container that is operable to be directly flash-heated by Joule heating.

[0058] The equipment is operable to perform a continuous process in which voltage is supplied to an external raw material heated by flash joules.

[0059] The transformed material can be a three-dimensional material.

[0060] The transformed material can be a two-dimensional material.

[0061] The transformed material can be a one-dimensional material.

[0062] The transformed material can be an amorphous material.

[0063] The transformed material can be selected from the following groups: FeS2, CoS2, CoS x Se y , CoSe, NiS2, NiSe2, Cu9S5, NbSe2, MoSe2, TiSe2, In2Se3, SnS2, SnS x Se y ,SnSe2,WSe2,WS2,Bi2S3,Bi x S y Se z ,Bi2Se3,TiN,LaBO3,Cu2Se,Cu 0.87 Se and its combinations and mixtures.

[0064] The converted materials may include chalcogenides, metals and / or alloys.

[0065] Reactors can be used to extract metals from ores and minerals.

[0066] The reactor can be used to extract metals from electronic waste sources.

[0067] External raw materials can be selected from the following groups: graphene, flash graphene, disordered graphene, anthracite, coconut shell-derived carbon, high-temperature treated biochar, activated carbon, calcined petroleum coke, metallurgical coke, coke, sub-graphite, carbon nanotubes, asphaltene, acetylene black, carbon black, ash, carbon fiber, graphite and combinations and mixtures thereof.

[0068] The external material can be converted into flash graphene by applying a voltage pulse, AC, DC or a combination thereof across the external material to subject the external material to a flash Joule heating process.

[0069] The external material is not graphite.

[0070] The electrodes can be connected to a DC voltage source.

[0071] The electrodes can be connected to a pulsed DC power supply.

[0072] The electrodes can be connected to an AC voltage source.

[0073] The electrodes can be connected to both DC and AC voltage sources.

[0074] The device may further include a controller that controls the flash Joule heating process applied by the electrodes via controlled electronic modulation. The controller may be selected from a group consisting of a variable frequency drive (VFD) controller, a pulse width modulation (PWM) controller, a proportional-integral-derivative (PID) controller, a three-phase controller, or combinations thereof.

[0075] Controlled electronic modulation can operatively utilize (i) DC current; (i) uniform, non-traveling AC current; or (iii) a combination thereof.

[0076] The device may further include an internal container electrode, which may be further operable to apply an internal container current through the internal material when one or more voltage pulses, AC, DC or a combination thereof are applied across the external material.

[0077] When one or more voltage pulses, AC, DC or a combination thereof are applied across the external material, the internal container electrodes can be operated to be independently controlled.

[0078] The device may further include a controller that independently controls the application of current through the internal material when one or more voltage pulses, AC, DC or a combination thereof are applied across the external material.

[0079] Individual tubes can be made from graphite foil rolled into cylinders, which are used as heating elements outside the inner quartz tube.

[0080] Graphite tubes can be used as both heating tubes and material holding tubes.

[0081] A gap or physical separation may exist between the graphite tube and the inner tube to suppress conductive heating of the inner tube and promote radiation as the primary heating mechanism.

[0082] The entire system can be sealed with a quartz tube.

[0083] An inert gas can flow through the gap to allow for heating via convection, conduction, and / or a combination thereof.

[0084] Reactive gases can flow into the chamber along with the raw materials to assist in chemical synthesis or decomposition.

[0085] The reactive gas can be chlorine.

[0086] Reactive gases can flow into the chamber along with the raw materials to assist in the chemical synthesis or decomposition of the ore.

[0087] Individual tubes can be reused multiple times.

[0088] Individual tubes can be made of graphite.

[0089] The system can be arranged in a concentric tube pattern, alternating between heating tubes and raw material holding tubes.

[0090] The tube can have a cylindrical shape.

[0091] The tube can have a non-cylindrical shape.

[0092] Non-cylindrical shapes can be semi-tubular.

[0093] Graphite foil can be clamped onto a copper or brass tube to provide electrical contact, while also providing a channel for inserting into a quartz tube that holds the material to be flash-heated.

[0094] Graphite cylinders can be used. Graphite cylinders can have sections to be heated, which have a reduced outer diameter or a longer length to increase the resistance in that section.

[0095] The support rod can be connected to the clamp to maintain structural rigidity and minimize strain on the graphite heating element.

[0096] Quartz cylinders or rods can be used to define the distance between clamps, which can withstand heat and do not undergo thermal expansion when heated, thereby reducing strain on the graphite foil cylinder.

[0097] Metal rods and springs can be used as tension elements, which are installed in insulating sleeves to prevent electrical conduction between clamps.

[0098] The components can be encapsulated in an outer cylinder, which is purged with an inert gas or evacuated to prevent oxidation of the electrically heated graphite tube.

[0099] The outer cylinder can be a quartz tube or a borosilicate tube.

[0100] The outer cylinder can be a pressurized metal tube.

[0101] Radiation shielding can be placed around the tubular graphite heater to reflect outgoing radiation back onto the heater element, thereby reducing the electrical energy required to maintain the temperature.

[0102] Radiation shielding components may include one or more of copper, nickel, molybdenum, and aluminum.

[0103] A gold coating can be used to enhance reflectivity.

[0104] The end caps can be made of PTFE or other insulating materials and are used to secure and seal copper or brass tubes.

[0105] Water can be added to copper or brass pipes for cooling.

[0106] When an inert gas is present, heat from the graphite tube can be transferred through the small gap via radiation, convection, and conduction.

[0107] The outer shell can be evacuated, and heat is transferred to the internal quartz tube through radiation.

[0108] Small openings or grooves can be made in the graphite tube to provide observation ports for the internal quartz tube and sample.

[0109] There must be no electrical connection between the materials inside the graphite tube and the quartz tube to allow for the independent application of external heating and electric fields.

[0110] Generally, in another embodiment, the invention is characterized by an apparatus comprising an inner container operable to receive raw material. The apparatus further comprises an outer container operable to provide a protective atmosphere or vacuum for a resistance heater. The apparatus further comprises a resistance heater within the outer container. The apparatus further comprises electrodes operable to provide AC or DC current to the resistance heater. The apparatus further comprises a plug within the inner container to contain the raw material therein.

[0111] Embodiments of the present invention may include one or more of the following features:

[0112] The inner container can be transparent. The resistance heater can be a tubular resistance heater. The resistance heater can be concentric within the outer container. The electrodes can be tubular electrodes.

[0113] The internal container can be a fused silica tube.

[0114] The inner container can be a transparent fused silica tube.

[0115] Resistance heaters can be rolled-up graphite foil.

[0116] The resistance heater can be a graphite tube.

[0117] Resistance heaters can be graphite tubes that taper at the center.

[0118] The outer container can be a fused silica tube.

[0119] The outer container can be a fused silica tube sealed with PTFE end caps and O-ring seals.

[0120] The outer container can be a metal tube.

[0121] The outer container can be a metal tube that can withstand pressure.

[0122] Electrodes may include metals selected from the group consisting of copper, brass, nickel, and combinations thereof.

[0123] The electrodes can be selected from copper electrodes, brass electrodes, nickel electrodes, and combinations thereof.

[0124] The device may further include graphite foil clipped onto the electrodes.

[0125] The device may further include a rigid support structure of tubes or rods, which minimizes strain on the resistance heater.

[0126] The tube or rod can be a quartz tube or rod.

[0127] Resistance heaters may include graphite foil.

[0128] The resistance heater can be a graphite tube.

[0129] Resistance heaters can be electrically heated by applying one or more voltage pulses, alternating current (AC), direct current (DC), or a combination thereof.

[0130] Applying one or more voltage pulses, alternating current (AC), direct current (DC), or a combination thereof can provide radiative heat transfer to the material inside the internal container.

[0131] The plug in the inner container can be conductive.

[0132] The plug inside the container can be connected to a high-voltage power source.

[0133] The plug inside the container can be connected to a high-voltage power source via wires.

[0134] The plug in the internal tube can be porous.

[0135] The plug in the internal tube can be porous to allow gas to enter or exit.

[0136] The device is operable to apply one or more voltage pulses, alternating current (AC), direct current (DC), or a combination thereof to the raw material in the internal container. Attached Figure Description

[0137] Figure 1A-1D An embodiment of the present invention is shown, which describes a cascade flash (FWF) Joule system operating in thermal conduction mode. Figure 1A A schematic description of FWF (Type 1) is shown. Figure 1B The current and temperature profiles for the 340 V FWF reaction are shown. Figure 1C A schematic description of a multiple FWF reaction (type 2) that allows for further (and potentially complete) conversion of the unreacted precursor is shown. Figure 1D A schematic description of anion exchange FWF reaction (type 3) for bypassing unexpected (and / or undesirable) side reactions is shown.

[0138] Figure 2 A circuit diagram of a capacitor bank discharge system that can be used in the FWF process is shown.

[0139] Figures 3A-3F A scheme for an FWF system operating in radiant heating mode is shown. Figure 3A A schematic diagram is shown illustrating a graphite tube heater, longitudinal section, and tube support for a device that allows radiative FWF heating. Figure 3B It shows Figure 3A A schematic diagram of the graphite tube heater, its longitudinal section, and the cross-sectional view of the tube support. Figure 3C A schematic diagram of a graphite tube heater, longitudinal section, and tube support is shown, illustrating an additional device that allows for radiative FWF heating. Figure 3D It shows Figure 3D A schematic diagram of the graphite tube heater, its longitudinal section, and the cross-sectional view of the tube support. Figure 3E This illustrates a description of independent electric fields / currents. Figure 3C A schematic diagram of a graphite tubular heater. Figure 3F A schematic diagram of a rigid graphite tube that can be used in an embodiment is shown.

[0140] Figure 4 A schematic diagram of an embodiment of FWF is shown, illustrating that the FWF reaction can be conceptually divided between an inner tube and an outer tube.

[0141] Figure 5 A-5F shows the internal tube temperature measurement of the FWF. Figure 5 A is a schematic description of the temperature measurement for a normal FWF reaction. Figure 5 B is a schematic description of the internal temperature by measuring the temperature of the skewed inner tube during the reaction. Figure 5C An infrared thermometer with an aligned laser is shown being focused onto a sample area to read time-dependent temperature changes during the FWF reaction. Figure 5D-5F The reaction kinetics during the FWF reaction are shown.

[0142] Figures 6A-6D The scalability of FWF is demonstrated. Figure 6A This is a photograph of 1.11 g of WSe2 powder obtained from a gram-scale reaction in an analytical balance. Scale bar: 10 cm. Figure 6B The XRD pattern of WSe2 prepared by gram-scale reaction is shown. Figure 6B Reference spectra are also provided (as shown below). Figure 6C This is the Se 3d XPS spectrum of WSe2 powder prepared by gram-scale reaction. Figure 6D This is the W 4f XPS spectrum of WSe2 powder prepared by gram-scale reaction.

[0143] Figures 7A-7H Different reactions and products from FWF are shown. Figure 7A This is a list of representative elements used in the FWF reaction. Small subsets represent the corresponding anionic components used in the preparation of inorganic compounds. Figure 7B This is a list of all final products with respect to the initial flash voltage and corresponding energy input. Unless otherwise stated, all syntheses used type I reactions of FWF. Figures 7C-7E These are ADF-STEM images and EDX plots of (C) SnS2, (D) SnSe2 and (E) Se-doped SnS2 (denoted as SnSxSey) to show reagent-dependent tunability and doping (substitution) capability. Figure 7F-7H These are ADF-STEM images and EDX plots of semiconductor materials (F) MoSe2 (n-type), (G) WSe2 (p-type), and (H) α-In2Se3 (n-type, ferroelectric).

[0144] Figures 8A-8D Selected area electron diffraction (SAED) patterns of SnS2, α-In2Se3, MoSe2 and WSe2 thin films are shown. Figure 8A SAED of SnS2 is shown. Figure 8B SAED of α-In2Se3 is shown. Figure 8C SAED of MoSe2 is shown. Figure 8D SAED of WSe2 is shown. All materials exhibit single-crystal properties in each slice.

[0145] Figures 9A-9B XRD and Raman spectra of the doping capability in Sn-based TMDs are shown. Figure 9A The diagram shows SnS2 and Se-doped SnS2 (denoted as SnS). x Se y XRD spectra of SnSe2 and SnSe2. Figure 9B The diagram shows SnS2 and Se-doped SnS2 (denoted as SnS). x Se y Raman spectra of SnSe2 and SnSe2, with images of the corresponding powders as a subset.

[0146] Figures 10A-10H The electrical performance characterization of the FWF product is shown. Figure 10A A schematic diagram of an experimental FET device geometry is shown. Schematic diagrams of the crystal structures of MoSe2, WSe2, and α-In2Se3 are shown within dashed boxes. Figure 10B Cross-sectional ADF-STEM images of MoSe2, WSe2, and α-In2Se3 in their respective FET devices are shown. Figure 10C-10EThe n-type MoSe2, p-type WSe2, and ferroelectric α-In2Se3 are shown at different V values. D Down (V) D Representative transfer curves (at constant drain voltage (V)) for 0.1 V and 1 V respectively. D Gate voltage (V) under G Drain current (I) D (Characteristics). The illustration shows an optical image of the FET device. The scale bar is 10 μm. Figure 10F-10G The n-type MoSe2 and p-type WSe2 FET devices are shown respectively from V G = −40 V to V G = 40 V representative output curve (at constant V) G V below D –I D characteristic). Figure 10H The durability characteristics of the ferroelectric In₂Se₃ FET device over 1,000 cycles are shown. The operating voltage is V. G = −40 V (for SET) and V G = 40 V (for RESET), and the voltage read is V. D = 1 V.

[0147] Figure 11A-11B A comparative analysis of tribological properties is presented. Figure 11A The time-dependent variation of the coefficient of friction (COF) over 120,000 measurements for reference alumina, commercial MoSe2, and FWF MoSe2 is shown. Moving average trend lines for reference alumina, commercial MoSe2, and FWF MoSe2 at 1 N are also presented. Figure 11B The force-dependent COF changes for reference alumina, commercial MoSe2, and FWF MoSe2 are shown.

[0148] Figure 12A-12F These are S / TEM images and SAED patterns of commercial (AC) MoSe2 and (DF) FWF MoSe2. Figure 12A A TEM image of commercial MoSe2 with an amorphous layer of about 20 nm at the edge of the sheet is shown. Figure 12B A TEM image of another region of commercial MoSe2 with an amorphous layer of about 10 nm at the edge of the sheet is shown. Figure 12C SAED patterns of commercial MoSe2 are shown, indicating polycrystalline and amorphous components. Figure 12D A TEM image of FWF MoSe2 is shown, in which there is little or no amorphous layer at the edge of the sheet. Figure 12EAn ADF-STEM atomic resolution image of MoSe2 is shown, revealing a clear and well-defined crystal structure at the edges of the sheet. Figure 12F The SAED pattern of FWF MoSe2 is shown.

[0149] Figures 13A-13D A comprehensive life cycle assessment of the FWF is shown. Figure 13A The cumulative energy demand analysis is shown. Figure 13B An analysis of the global warming potential is presented. Figure 13C-13D The following figures show the (C) cumulative water consumption analysis and (D) preliminary estimated product cost (techno-economic analysis) for the production of 100 g MoSe2 using FWF, compared to autoclave (Mg-assisted) and CVT synthesis. CO2e, CO equivalent. Detailed Implementation

[0150] This invention relates to a method and system for flash Joule heating, specifically including a method and system for cascade flash (FWF) Joule heating.

[0151] A general non-equilibrium flash-wheat-free (FWF) Joule heating synthesis scheme has been discovered, featuring an ultrafast thermal conduction mechanism that enables the rapid synthesis of various compounds within seconds. In this FWF process, flash-wheat-free reactions can be performed, where the target feedstock is placed in a small reaction vessel within a larger reaction vessel, positioned between typical carbon-based flash feedstocks. This allows the internal target feedstock to react without contamination from external flash feedstocks and imposes no limitations on the resistivity of the target feedstock.

[0152] FWF overcomes the limitations of traditional equilibrium-based large-scale synthesis methods, achieving faster reaction rates and reducing dependence on solvents, water, and energy. FWF also provides a versatile, efficient, and scalable approach for producing a wide variety of inorganic compounds, with excellent control over synthesis parameters to produce phase-selective and single-crystal bulk powders. FWF demonstrates flexibility in material modification through doping and scalability, offering an environmentally friendly and cost-effective route for designing inorganic materials. Furthermore, FWF materials enable diverse applications; for example, MoSe2 exhibits superior tribological properties compared to commercially available MoSe2.

[0153] A further difference between the FWF heating process and the FJH process lies in the two distinct heating methods: conduction heating and radiation heating. While FJH relies on a direct current flowing into the material to induce resistance heating within the sample, FWF relies on a heat transfer method. Heat conduction typically dominates when a medium for heat transfer is present. When the FWF process is performed under ambient conditions, in a pressurized system, in direct contact with material heated by flash Joule heating, or for short periods, the primary heat transfer method is heat conduction.

[0154] On the other hand, when the FWF process occurs in a vacuum, does not involve direct contact with the material being flash-heated by Joule, or is carried out over a long period of time, radiative heating methods dominate because there is no medium through which heat can travel. Radiation includes wavelengths from infrared to ultraviolet, depending on the temperature of the material being flash-heated by Joule.

[0155] Another aspect of heating may be caused by exothermic or endothermic reactions within the internal container. When the internal reaction is exothermic (or endothermic), the internal tube can have a higher (or lower) temperature than the external material heated by flash Joule heating.

[0156] Cascaded flash joule heating (FWF) process

[0157] Figure 1A A schematic description of the FWF used in embodiments of the invention is shown. As illustrated in pre-processing schematic 100, the FWF process involves using a system with two containers (typically quartz containers): an outer flash container 103 filled with an inexpensive conductive material 105, such as metallurgical coke; and an inner semi-closed reactor 108 containing the target reagent 107 (precursor). Pre-processing schematic 100 shows that the system may further include a copper cotton plug 104 (or a graphite disc) that can contact the conductive material 105 and the electrode 106 (graphite, copper, or any conductive refractory material).

[0158] As shown in schematic diagram 101 during the process, during the FWF process, the system is in the ambient atmosphere and flash Joule heating (FJH) is applied to the external container. The FJH process is carried out through a custom capacitor bank discharge system. Figure 2 [DengII 2022]. Current 109 flows through the conductive material 105 in the outer container 103, causing resistive Joule heating and generating a high temperature of approximately 2000°C, as measured by an infrared camera equipped with an aligned laser. Figure 1B . Figure 1B The current profile 121 and temperature profile 122 for the 340 V FWF reaction are shown. Dashed boxes 123-125 represent duty cycle regions of 10%, 20%, and 50%, respectively.

[0159] The intense heat 110 generated in the conductive material 105 of the outer container 103 is then transferred to the inner container 108 via thermal conduction, allowing for ultrafast heating of the reagent 107 in the inner tube 108. The voltage used for synthesizing the material can be varied, such as in the range of 220 V to 340 V in the embodiments discussed and described herein. To minimize the risk of explosion during the reaction and potential damage to the custom capacitor bank, a pulsed duty cycle is used to regulate the current. This technique uniformly distributes the current and corresponding resistance heating across the sample during the utilized 5-second reaction duration. The pulsating discharge via the duty cycle also allows for continuous variations in temperature, pressure, and volume to trigger a non-equilibrium, kinetically controlled reaction while forming a specific target product 111 in the inner container 108, as illustrated in the post-processing schematic 102 [Dong 2022]. Simultaneously, the conductive material 105 of the outer container 103 (which is metallurgical coke) is transformed into disordered graphene to generate additional value-added chemicals in a single reaction. The entire process can occur in less than 5 seconds, highlighting the ultrafast kinetics of the FWF.

[0160] The internal container is not required to contain conductive materials. For example, this method can be used to achieve the crystal growth of several transition metal dichalcogenides. These target products in the inner tube are different from the conductive carbon reactants in the outer tube, which can be converted into other products, such as disordered flash graphene.

[0161] In this embodiment, the parameters used for FWF Joule heating may include the following:

[0162] a. The external material responsible for Joule heating has sufficient resistance to allow the current to heat the sample, and sufficient conductivity to allow the current to flow, typically 1-10 ohms.

[0163] b. The external material is in electrical contact with the external electrode, allowing current to flow from one side to the other through the external tube.

[0164] c. There are no restrictions on the resistivity of the target material in the internal tube.

[0165] d. The internal material can, but does not necessarily have to, be in electrical contact with the external material. If the lid in the internal container is conductive, such as having copper or graphite or both, it can allow current to flow through the internal container. Alternatively, the lid in the internal container can restrict current flow through the internal container, like a ceramic lid.

[0166] e. Due to the chemical inertness, high thermal shock resistance, and high resistivity of fused silica, the internal reaction vessel can be constructed of fused silica. (In the example presented herein, a fused silica internal reaction vessel is used). Alternatively or additionally, the internal reaction vessel can be or may include ceramic or concrete.

[0167] f. This method allows for the formation of products that cannot normally be formed or produced in high yields by conventional flash Joule heating.

[0168] g. The chemical products of these reactions are usually oxidizing products.

[0169] h. This method can be used to synthesize single-crystal materials with quality comparable to those produced by chemical vapor deposition.

[0170] i. When conductive carbon raw materials are used in the outer container, the carbon is converted into high-quality randomized flash graphene, which can be reused multiple times as the raw material contents of the outer container.

[0171] j. External raw materials and internal reactants in a mass ratio of approximately 8:1 can be used for these reactions.

[0172] k. The reaction energy input per gram of internal raw material can be approximately 48 kJ / g to 90 kJ / g.

[0173] These reactions can be carried out in a vacuum, or under ambient atmospheric conditions, or in an internal or external reaction vessel under other gases.

[0174] The setup for the FWF process complements the system and method for synthesizing graphene by flash Joule heating disclosed and described in Tour '967 PCT application. The FWF method has been used in conjunction with pulse-width modulated DC electrical pulses for discharging capacitor banks, and can also be accomplished using unmodulated DC, AC pulses, or combinations thereof. These reactions have been scaled up in an internal container to 1 gram of target product, and scale-up to well greater than 1 gram of target product is conceivable, i.e., from several kilograms to tens or hundreds of kilograms.

[0175] Figures 3A-3F A scheme for an FWF system operating in radiative heating mode is illustrated. Radiative heating is dominant when the FWF process occurs in a vacuum, does not involve direct contact with the material being flash-heated by Joule, or is carried out for extended periods. For these reaction environments, radiative heating methods are dominant because there is no medium through which heat can travel. Radiation includes wavelengths from infrared to ultraviolet, depending on the temperature of the material being flash-heated by Joule.

[0176] Figure 3AA schematic diagram of a graphite tube heater 300 (longitudinal section, tube support) describing an apparatus that allows for radiative FWF heating is shown. The graphite tube heater 300 is viewed longitudinally. The heating element is rolled graphite foil (graphite double layer 312 and graphite single layer 313). The retainer responsible for maintaining the rigidity of the apparatus consists of three quartz tubes (covered with Cu foil): an outer quartz tube 303 (which may have a 63 mm ID), a quartz tube sample holder 315 (which may have an 8 mm ID and a 12 mm OD), and a third quartz tube (not shown). Other features of the graphite tube heater 300 include water cooling 301, end plugs 302 (such as PTFE end plugs), nuts 304, springs 305, bushings 306 (such as ceramic bushings), shaft clamps 307, quartz tube support gaskets 308 (which may be covered with Cu foil), threaded / tension bars 309 (such as 6-32 threaded / tension bars), radiation reflectors 310, gaskets 311 (such as Cu gaskets), tubes 314 (such as Cu or brass tubes with 5 / 8” OD), N2 316, a viewpoint in the reflector 317, O-rings 318, and vacuum 319. Springs 305 can maintain constant compression, shaft clamps 307 are two-part clamps with ¾” OD and 2” OD, and the graphite sheet can be 0.005” thick and narrowed in the middle to provide a single tubular layer. Figure 3A The wiring connection at the copper tube end of the graphite tube heater 300 is also not shown.

[0177] Figure 3B A schematic cross-sectional view of a graphite tube heater 300 is shown, allowing material to evaporate and deposit onto a selected desired substrate (metal or insulating material). The viewpoint of the graphite tube heater 300 is cross-sectional and shows further features of the split sleeve 325 (such as a split Cu sleeve), the deposition plate 329 (such as a deposition Al or Cu plate), and the evaporation plate 330 (such as an evaporation carbon / graphite plate). Fixtures and electrodes are shown in dashed lines in the graphite tube heater 300.

[0178] To change the length of the graphite tube heater 300, the tubular gasket 308 and the threaded / tension bar 309 need to be cut to the appropriate length.

[0179] Figure 3C A schematic diagram of a graphite tube heater 340 (longitudinal section, tube support) is shown, illustrating a device that allows for radiative FWF heating. Similar to... Figure 3A The viewpoint of the graphite tube heater 340 is longitudinal. The heating element is made of rolled graphite foil (graphite double layer 312 and graphite single layer 313), with four rods 343 (such as quartz rods 4 mm) acting as support holders (two of which are in…). Figure 3C(As shown in the figure). The graphite tube heater 340 is similar in features to the graphite tube heater 300, wherein an O-ring retainer 341 is also shown.

[0180] Figure 3D A schematic cross-sectional view of a graphite tube heater 340 is shown, which allows material to evaporate and deposit onto a selected desired substrate (metal or insulating material), with four rods 343 acting as support holders. The viewpoint of the graphite tube heater 340 is in section. Wrappers and gaskets 351 (such as Cu foil wrappers and gaskets) are also shown.

[0181] The graphite tube heater 340 offers easier length adjustment; however, it may be more fragile.

[0182] The graphite tube heaters 300 and 340 have a radiation reflector 310 to reduce losses from the output radiation.

[0183] In this embodiment, the internal raw material is non-conductive, and conductive materials cannot be easily added to it (as this would affect the resulting product). In such cases, the heat originates from the FJH process occurring in the outer container. In this case, the plug of the inner container does not need to be conductive; for example, the plug of the inner container could be ceramic. However, there are embodiments in which it would be advantageous for the inner container to have plugs at each end serving as conductive electrodes. For example, the internal raw material itself is conductive, or becomes conductive during the FJH process. In such cases, the embodiment will have a current flowing through the internal raw material in the inner container, which can reduce the activation energy of the desired thermal process occurring within the inner container.

[0184] Figure 3E A schematic diagram of a graphite tube heater 360 is shown, which is a graphite tube heater 340 with an independent electric field / current to provide current through the internal feedstock in the internal container during the FJH process. Figure 3E As shown, a resistive or non-conductive sample 363 is placed inside an internal quartz tube. Electrodes 369, connected to wires 361, are placed at each end of sample 370. Wires 361 are heat-resistant (such as nickel, tungsten, or carbon rods). Wires 361 are insulated outside the quartz tube. Wires 361 are connected to a high-voltage power supply, AC or DC 365. Wires 368, providing the high current required to heat the tubular graphite heater, are clamped to a copper (or brass) tube 314 using cable clamps 367. Wires 368 are connected to a welding power source or a power source that can provide a high current 366. The end of the quartz sample holding tube can be sealed with a plug / fittings 364 (which allows gas ingress and collection). The tubular graphite radiant heater 360 can be operated separately from the HV power supply 365. This allows for completely independent control of the heating of the sample and the electric field or current applied directly to sample 363.

[0185] By providing fittings that allow gas entry and collection, gases such as chlorine can be introduced into the sample 363 within the inner tube. Therefore, the graphite tube heater 360 can be used to extract metals from ores and minerals, such as lithium from spodumene, by Joule heating or electrothermal chlorination. [Tour's 556 application].

[0186] The graphite tube heater 360 can also be used, for example, to extract / remove from waste (a) metals such as electronic waste, such as printed circuit boards, or industrial waste such as fly ash or bauxite residue (such metals may be metals essential to the electronics industry, such as rare earth elements, gallium, tantalum, indium, or germanium); (b) metals from waste batteries, such as lithium, cobalt, nickel, or manganese; and (c) iron from bauxite residue, so that the remaining aluminum can be further purified.

[0187] Figure 3F A schematic diagram is shown using a rigid graphite tube 370 as a heating element, where a thinner section of graphite serves as the heating zone due to resistance differences. The rigid graphite 370 is machined to be thinner at the center. For example, for a rigid graphite tube 380 with a longitudinal length 375 of 3.8” (where ID 372 is 0.5” and OD 374 is 1”), the intermediate section length 373 can be 1.4”, where the annular length 372 is approximately 0.03” (i.e., the outer diameter of the intermediate section is approximately 0.53”). This type of rigid graphite tube 370 will have higher resistance in the intermediate section, where heating will occur. The rigid graphite tube 370 can be used as a lace for rolled graphite foil in graphite tube heaters 300, 340, and 360. Larger shaft clamps can also be used to accommodate larger end diameters.

[0188] The workflow of a representative FWF reaction flash Joule heating process is as follows: Figure 4 The above is shown in the figure, and further summarized as follows:

[0189] a. In step 401, the reactants are mixed and measured. For example, the target reactant raw materials are mixed in a mortar and pestle at the desired weight ratio. The total mass of the mixture is approximately 500 mg.

[0190] b. In step 402, the reactants are filled into the inner container and cap. For example, the reactant raw material mixture is placed in a small quartz tube. The tube is capped at both ends with an inert material.

[0191] i. The quartz tube is approximately 4 cm long, with an inner diameter of 8 mm and an outer diameter of 10 mm. Therefore, the tube wall is only 1 mm wide. The cap is typically made of a cylindrical piece of graphite and usually contacts a cylindrical copper wire, called a gasket. The copper wire may extend outside the tube for better electrical contact within the sample. The cap can also be made of an insulating ceramic material.

[0192] c. In step 403, the conductive feedstock is measured. For example, carbon feedstocks are chosen such that the resistance across the main reaction vessel is 1–10 Ω. Small pieces of metallurgical coke, measuring 4–5 grams (most commonly 5 grams), are used in almost all the representative synthesis discussed herein (unless otherwise stated). Again, metallurgical coke is a common feedstock for FWF.

[0193] i. In this type of test, the metallurgical coke used was obtained from SunCoke. It was then ground and sieved to a size between 0.30 and 0.84 mm. It should be noted that this is finer than the metallurgical coke used for conventional flash Joule heating when manufacturing graphene.

[0194] d. In step 404, the outer tube is filled and capped with the inner tube (containing the reactants) and conductive material. For example, a quartz tube is selected and capped at one end with a graphite electrode. A copper gasket is typically placed inside the graphite electrode. The outer tube is filled with approximately 1 / 3 of the selected metallurgical coke. The filled inner reaction tube is then placed inside the outer tube on top of the conductive material (metallurgical coke). The remaining metallurgical coke is then poured around the inner tube, such that the metallurgical coke surrounds the inner tube on all sides. The outer tube is then capped with a second graphite electrode and optionally a copper gasket. The tube is then longitudinally compressed to improve electrical contact.

[0195] i. The outer tube is approximately 10 cm long, with an inner diameter of 16 mm and an outer diameter of 20 mm. The inner tube is typically located at the exact center of the outer tube. When measured across the two outer graphite electrodes, the resistance of these nested tubes is typically about 2–5 Ω.

[0196] e. In step 405, the FWF process is performed. For example, the nested tubes are then subjected to DC flash Joule heating. Current flows from one external graphite electrode through the metallurgical coke in the external tube to the other graphite electrode. For a reaction of this scale, 24–45 kJ of energy is typically used. Flash heating is performed using a pulse-width modulated DC signal, with a three-step duty cycle pattern of 10% for 1 second, 20% for 0.5 seconds, and 50% for 5 seconds.

[0197] f. In step 406, the generated target material is removed from the inner tube, and in step 407, the product is removed from the outer tube.

[0198] Internal tube temperature and reaction kinetics

[0199] Internal tube temperature measurements are crucial for understanding the synthesis environment and kinetics, as the synthesis-temperature-composition relationship can be used to further optimize the FWF process. Before conducting a model FWF reaction to convert tin(II) chloride dihydrate salt (SnCl2·2H2O) and sulfur to tin disulfide, an attempt was made to measure the internal tube temperature by moving the internal tube to the surface of the external tube. Figure 5 A-5F. Figure 5 The configuration shown in A allows for the acquisition of the temperature of the external tube, and as described above ( Figure 1B ). Figure 5 The configuration shown in B allows an infrared thermometer equipped with an aligned laser to measure the internal tube temperature in the FWF process. (For) Figure 5 For the two temperature measurements of A-5B, the laser-assisted thermometer was positioned 10 cm above the sample. The current may differ between the two configurations because the resistance for the right configuration may differ due to the filling of metallurgical coke compared to the left configuration. (However, the total energy input remains constant.) See also: Figure 5C Samples in both configurations exhibited similar resistances of 1.5 Ω, allowing for a good comparison between the modified FWF process and the normal FWF process. The inner tube exhibited a significantly higher maximum temperature (approximately 2550°C) than the outer tube (approximately 2000°C). This unexpected result led to an investigation into whether other heat sources were causing the higher inner tube temperature.

[0200] To accurately describe the internal tube temperature, the total heat ( It is described as a function of three key heating sources: Stefan-Boltzmann radiative heating (E... rad ), heat conduction heating from external FJH reaction (E) TCH ) and heat of reaction (E) ΔH The heat source that contributes to the internal tube temperature is calculated using equations (1)-(4) with the following parameters.

[0201] (1)

[0202] Where A = 0.003 m 2 e = 0.7; σ = 5.67 × 10 -8 W / m 2 ∙K 4 k = 1.4 W / m∙K (thermal conductivity of quartz at 25℃).

[0203] (2)

[0204] Where c2 = 0.4 J / g∙K; m2 – 0002 kg.

[0205] (3)

[0206] Where P0 is chosen such that The integral over time is 1, 2, 3, 5, or 10 kJ; t o = 1.5 s; c = 0.05 s.

[0207] (4)

[0208] Calculations show that, due to the short reaction time, the contribution of radiative heating will be minimal, indicating that the heat of reaction (E) ΔH The enthalpy (ΔH) is the primary factor causing the internal tube temperature to be higher than the external tube temperature. Precise measurement of ΔH is impossible because enthalpy is a state function and can only be measured when the reaction is at equilibrium. However, the total heat released and the heat release rate during the reaction can be inferred by calculating the reaction enthalpy at a given temperature and measuring the time-dependent change in internal tube temperature for the reaction of interest. For example, the reaction enthalpy for the synthesis of SnS2 at 2000 °C is approximately -410 kJ / mol. Since the total amount of SnCl2·2H2O used in this reaction is 1.0 g, the maximum heat that the internal reactants can release is 1.8 kJ. The time required for the reaction to complete can be inferred when heating stops. When the exothermic reaction stops 0.4 seconds after entering the FWF process, the heat release rate of the reaction is calculated to be 4.5 kJ·s. -1 .

[0209] Using equations (1)-(4), the simulated temperature profile describes the internal tube temperature by solving the differential equations. As shown, when the heat of reaction is 2 kJ, the temperature profile is similar to the observed temperature of about 2550℃ (about 2500℃). Figure 5 B. This result indicates that the heat released during the reaction significantly affects the results and varies across the different FWF reactions as discussed and described herein. Therefore, careful consideration of the specific reaction of interest is required to accurately characterize the internal tube temperature.

[0210] FWF reaction type

[0211] The FWF process can be further fine-tuned in other ways. For example, by employing different reaction designs, certain problems, such as slow rates and side reactions, can be mitigated, thereby producing materials that are difficult to prepare by other methods. One type, referred to herein as "Type 1 reaction," in... Figure 1A As shown in the schematic diagram, as discussed above.

[0212] Another type, referred to in this paper as "Type 2 response", in Figure 1CThe diagram shows that continuous flash evaporation for 2 to 5 times solves the problem of partial conversion. Figure 1C A schematic diagram 131 of preprocessing with target reagent 133 (precursor) and a schematic diagram 132 of postprocessing with target product 135 after 2-5 consecutive reactions 134 are shown. For example, the initial attempt to convert tungstic acid (WO3·H2O) to WS2 did not result in complete conversion, as indicated by the presence of unreacted precursors in XRD analysis. This is believed to be attributed to the slow reaction rate. However, after successive FWF reactions, near-complete conversion was achieved. XRD data showed that the initial WO3 signal weakened with each subsequent reaction, indicating that WO3 was almost completely converted to WS2 in three FWF reaction cycles.

[0213] Another type, referred to in this article as "Type 3 response", is... Figure 1D As shown, it is an anion exchange reaction, which can also resolve reactions that are difficult due to unexpected side reactions. Figure 1D A schematic diagram 141 shows a preprocessing step with target reagent 143 (a precursor, which is a metal precursor containing SeS2), and a schematic diagram 142 shows a postprocessing step with target product 145 (anion-exchanged product) following anion exchange reaction 144 (promoted by S or Se). For example, a side reaction of Bi(NO3)3·5H2O with Se results in the release of brown gas (all reactions were carried out in a well-ventilated fume hood). After FWF with these solid precursors, the resulting product is a mixture of BiSeO2 and BiSeO5, indicating that the gas release was due to an unintended oxidation reaction. This unwanted oxidation reaction was successfully bypassed using a type 3 reaction. Bi2Se3 is synthesized using Bi(NO3)3·5H2O and SeS2, which initially produces Bi2S. x Se y The intermediate was then treated with Se to promote the anion exchange reaction. Similarly, by changing the added chalcogenide element to S, Bi₂S₃ was obtained. X-ray diffraction (XRD) analysis showed that complete transformation occurred to produce pure Bi₂S₃ or pure Bi₂Se₃ as needed.

[0214] Representative synthetic methods

[0215] Unless otherwise specified, all reagents used in these representative synthetic methods were used exactly as received from the manufacturer. Unless otherwise specified, all reactions were carried out using type 1 reactions.

[0216] SnS2

[0217] 0.25 g of SnCl₂∙2H₂O (Alfa Aesar, reagent grade) was ground together with 0.25 g of sulfur (Millipore-Sigma) using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0218] SnS x Se y

[0219] 0.25 g of SnCl₂∙2H₂O was ground together with 0.48 g of selenium sulfide using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0220] SnSe2

[0221] 0.25 g of SnCl₂∙2H₂O was ground together with 0.26 g of selenium using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0222] SnSe2-gram level

[0223] 1.0 g of SnCl₂∙2H₂O was ground together with 1.05 g of sulfur using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0224] Bi2S 3- Type 1

[0225] 0.25 g of Bi(NO3)3∙5H2O (Millipore-Sigma) was ground together with 1.0 g of sulfur using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing. It should be noted that the material synthesis can be accomplished by either direct flash evaporation (Type 1) or anion exchange flash evaporation (Type 3).

[0226] Bi x S y Se z

[0227] 0.25 g of Bi(NO3)3∙5H2O was ground together with 0.25 g of selenium sulfide (Millipore-Sigma) using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0228] Bi2S3-Anion Exchange Pathway (Type 3)

[0229] Using a mortar and pestle, 0.25 g of the prepared Bi2S x Se y Mix with 1.0 g of S. Place the resulting powder into an 8 mm quartz tube with a graphite pad and extrude copper wire at each end of the tube. Then place the tube into a 15 mm quartz tube, which is subsequently filled with 5.0 g of metallurgical coke. These tubes are subjected to rapid Joule heating at 340 V. Collect the resulting powder without further purification or washing.

[0230] Bi2Se3- anion exchange route (type 3)

[0231] Bi(NO3)3∙5H2O (Millipore-Sigma) immediately forms a brown gas upon mixing with Se (Millipore-Sigma). Therefore, the anion exchange route is used instead of the direct synthesis route of Bi2Se3. Figure 1D Using a mortar and pestle, 0.25 g of the prepared Bi2S x Se yMix with 1.0 g of Se. Place the resulting powder into an 8 mm quartz tube with a graphite pad and extrude copper wire at each end of the tube. Then place the tube into a 15 mm quartz tube, which is subsequently filled with 5.0 g of metallurgical coke. These tubes are subjected to rapid Joule heating at 300 V. Collect the resulting powder without further purification or washing.

[0232] NiS2

[0233] 0.25 g of Ni metal powder (Millipore-Sigma, <150 µm particle size) was ground with 1.0 g of sulfur using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 220 V. The resulting powder was collected without further purification or washing. Trace amounts of NiS were detected in the XRD pattern.

[0234] NiSe2

[0235] 0.25 g of Ni metal powder was ground together with 1.0 g of Se using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0236] CoS2

[0237] 0.25 g of Co(II,III) oxide (Millipore-Sigma, <50 nm particle size) was ground with 1.0 g of sulfur using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0238] CoS x Se y

[0239] 0.25 g of Co(II,III) oxide was ground together with 1.0 g of selenium sulfide using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0240] CoSe

[0241] 0.25 g of Co powder (Millipore-Sigma, -100 mesh) was ground together with 1.0 g of selenium using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0242] MoSe2

[0243] 0.25 g of Mo metal powder (Alfa Aesar, APS 3-7 μm) was ground together with 1.0 g of selenium using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0244] WSe2

[0245] 0.25 g of W metal powder (Alfa Aesar, APS 1–5 μm) was ground with 1.0 g of selenium using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0246] WSe2-gram grade

[0247] 1.0 g of W metal powder was ground together with 1.3 g of Se using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to flash Joule heating at 340 V. Due to the rapid volume expansion and degassing of Se during the reaction, 100% powder recovery was not possible. The residual powder in the inner tube was collected without further purification or washing. The collected powder was weighed; the recovery rate was 59%, with a conversion of approximately 100%. See also Figure 5 A-5D.

[0248] NbSe2

[0249] 0.25 g of Nb metal powder (Thermo Scientific, -325 mesh) was ground together with 0.67 g of selenium using a mortar and pestle. The molar ratio between Nb and Se is important for Nb, as Nb further reacts with Se to produce Nb₂Se₉. The resulting powder was placed in an 8 mm quartz tube with a graphite pad and extruded copper wire at each end. This tube was then placed in a 15 mm quartz tube subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing. A small amount of unreacted Nb was detected in the XRD pattern.

[0250] FeS2

[0251] 0.25 g of Fe₂O₃∙xH₂O (Millipore-Sigma, catalyst grade, 30-50 mesh) was ground together with 1.0 g of sulfur using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 220 V. The resulting powder was collected without further purification or washing. XPS analysis of the resulting powder showed a significant oxygen concentration, suggesting that further modifications (such as type 2 reactions) may be necessary to prepare a cleaner material.

[0252] α-In₂Se₃ (α-phase In₂Se₃)

[0253] 0.42 g of In metal teardrop pellets were mixed with 0.84 g of Se. The resulting mixture was placed in an 8 mm quartz tube with a graphite gasket, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube subsequently filled with 5.0 g of metallurgical coke. The tube was subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0254] TiSe2

[0255] 0.25 g of Ti metal powder (Johnson Matthey Catalog Company, -325 mesh) was ground together with 1.0 g of Se using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0256] Cu 0.87 Se

[0257] 0.25 g of Cu metal powder was ground together with 1.0 g of selenium using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0258] Cu9S5

[0259] 0.25 g of Cu metal powder was ground with 1.0 g of sulfur using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 300 V. The resulting powder was collected without further purification or washing.

[0260] Cu2Se - Byproduct

[0261] The cascade flash evaporation reaction degasses selenium gas to the outer tube for use in the reaction within the inner tube with more than 1 g of selenium powder. This high-throughput degassing causes the copper wool (acting as a separator) to react with the selenium gas. The resulting crystals are ground and the powder is collected without further purification or washing.

[0262] TiN

[0263] 0.25 g of Ti metal powder (Johnson Matthey Catalog Company, -325 mesh) was ground with 1.0 g of selenium using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed inside a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0264] LaBO3

[0265] 0.25 g of La(NO3)3·6H2O powder (Millipore-Sigma) was ground together with 0.5 g of amorphous boron using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to rapid Joule heating at 340 V. The resulting powder was collected without further purification or washing.

[0266] WS2* - Multiple Flash Evaporation (Type 2)

[0267] 0.25 g of WO3·H2O (Millipore-Sigma) was mixed with 1.0 g of S using a mortar and pestle. The resulting powder was placed in an 8 mm quartz tube with a graphite pad, and copper wire was extruded at each end of the tube. This tube was then placed in a 15 mm quartz tube, which was subsequently filled with 5.0 g of metallurgical coke. These tubes were subjected to flash Joule heating at 340 V. Due to incomplete conversion and significant residue of the initial precursor, the reaction was repeated twice more (a total of three times) with the synthesized powder and 1.0 g of sulfur to convert the initial tungstate to WS2. Trace amounts of tungstate were observed.

[0268] Product and doping / substitution capabilities

[0269] The FWF method can be used for the general synthesis of a variety of compounds. As discussed above, 10 TMDs, 3 Group XIV dichalcogenides, and 9 non-TMD materials have been prepared as representative examples by controlling the voltage and reagents individually. Figure 7A Table I.

[0270] Table I

[0271] The final products obtained from the FWF reaction are distinguished by transition metal dichalcogenides (TMDs) and non-TMD materials.

[0272]

[0273] XRD, XPS, and / or (scanning) transmission electron microscopy (S / TEM) characterization confirmed successful synthesis, highlighting consistent production of the desired product. A variety of solid-state reagents can be used as precursors, including metal powders (e.g., Ni, Mo, W), metal chlorides (e.g., SnCl₂·2H₂O), metal oxides (e.g., cobalt(II, III) oxides, iron oxide hydrates), metal nitrates (e.g., Bi(NO₃)₃·5H₂O), and hydrated salts. The voltage for each reaction is optimized to produce the desired final product. Figure 7B The initial input voltage is directly related to the input energy; that is, the total energy transferred to the reaction can be calculated using the following formula:

[0274] (5)

[0275] Where C is the capacitance (624 mF) and V is the flash voltage. For example, when 5 g of coke is flashed at 340 V, the total energy transferred is approximately 7.2 kJ·g. -1 Since the current does not flow through the internal tube, the contribution of the internal tube's mass is negligible.

[0276] The corresponding energy per gram of metallurgical coke, expressed in kJ, is also indicated. However, similar to the method described above, the internal tube temperature should be calculated and measured to describe the total heat release and the heat release rate, respectively. This multifunctional synthesis technique overcomes not only the conductivity requirements of carbothermic and thermal shock methods (including FJH), but also the limitations of other synthesis schemes (such as hydrothermal synthesis), where the solubility and type of the initial precursor play a crucial role in the formation of the product of interest [Joo 2011]. Although most of the compounds synthesized in this experiment focused on sulfides, selenides, and layered materials [Du 2020; Feng 2022], the formation of titanium nitride (TiN) and lanthanum borate (LaBO3) was demonstrated, indicating that FWF can be used as a general method for the synthesis of a wide variety of inorganic compounds.

[0277] It is also possible to dope (substitute) various compounds using FWF by simply changing the initial precursor. Three different chalcogenide-based reagents, S, SeS₂, and Se, were used as the corresponding anions in the Sn-based system to observe reagent-dependent tunability and doping capability. See also Figures 7C-7E As shown by annular dark-field scanning transmission electron microscopy (ADF-STEM) and energy-dispersive X-ray spectroscopy (EDX), SnS2 ( Figure 7C ) and SnSe2 ( Figure 7DAtomic resolution images of these compounds indicate that their synthesis was successful; EDX also showed similar results to ADF-STEM imaging, which detected Sn and S or Se respectively. Notably, Se-doped SnS2 (denoted as SnS) was formed by simply replacing the initial precursor with SeS2. x Se y () Figure 7E EDX spectra show a uniform distribution of Se with high crystallinity, as observed in the ADF-STEM images. Due to the 2:1 ratio of S to Se, SnS... x Se y The Raman spectra and XRD patterns of the samples exhibited similar characteristics to SnS2. Furthermore, all sections analyzed by S / TEM (scanning / transmission electron microscopy) showed single-crystal orientation. Figures 8A-8D This further demonstrates the ability of FWF to produce phase-selective and single-crystal bulk powders, results rarely observed in other non-equilibrium methods.

[0278] like Figure 9B As shown in illustration 901, for SnSe2, via Figure 9A The XRD spectrum shown confirms the formation of a small amount of SnO2 on the surface (also confirmed by EDX mapping (see [link]). Figure 7D )).like Figure 9B Illustrations 901-903 further show that the color of the powder changes abruptly from yellow (SnS2) to red (SnS2). x Se y This demonstrates that doping and dislocations cause band gap shifts in materials. [Chen 2011; Choi 2018]. This provides a simple and rapid method for doping other atoms into a system, demonstrating doping procedures for applications in electronics [Shi 2020], catalysis [Dou 2020], and energy storage. [Zhu L 2023; Zhu W2023].

[0279] Electron microscopy characterization and electrical properties of FWF materials

[0280] FWF allows for the synthesis of phase-controlled materials. MoSe2 and WSe2 ( Figure 7F-7G ADF-STEM images of In2Se3 show that these materials exhibit a hexagonal atomic configuration as well as 2H phase and AB stacking, revealing their energy-favorable structures in the analyzed lamellae [Förg2021]. Compared to the FJH method [Luong 2020], which previously produced metastable flash graphene with a disordered layer configuration, FWF does not involve a current passing through the sample during synthesis. This may explain the highly regular ordering in the stacking. For In2Se3, as shown by the ADF-STEM images ( Figure 7HAs shown by XRD, only the α phase (α-In2Se3) exists in the thin section, indicating that the currently optimized FWF is a selective process. [Han 2023].

[0281] Understanding the electrical properties of FWF products is important because these synthesized materials can be widely used in many semiconductor applications. MoSe2, WSe2, and α-In2Se3 flakes are used as representatives because they exhibit n-type semiconductor, p-type semiconductor, and n-type ferroelectric behavior, respectively. To characterize the electrical properties, the FWF materials were mechanically exfoliated, and field-effect transistor (FET) devices 1000 were fabricated on SiO2 / Si substrate 1001 using conventional photolithography. Figure 10A .

[0282] for Figure 10A The fabrication of device 1000, as shown in the schematic diagram, involved MoSe2 1007, WSe2 1008, and α-In2Se3 1009 (both FWF α-In2Se3 and commercial single-crystal α-In2Se3 were purchased from 2D Semiconductors®). Samples were fabricated on SiO2 (285 nm) / Si substrates using typical mechanical exfoliation methods. The thickness of the layers was verified by optical contrast, and subsequently determined using cross-sectional TEM. To form electrical contacts, source 1003 and drain 1002 patterns were fabricated using conventional photolithography techniques, with a channel length of 3 μm, and then evaporated using an electron beam evaporator at approximately 10 nm. -8 The pressure of Tor and 2.0 Å·s -1 A 50 nm layer of Au metal was deposited at a deposition rate of [missing information]. To remove residual photoresist, the sample was immersed in an acetone bath for 6 to 12 hours, followed by gentle purging of the solution with N2 gas. Finally, to enhance the interfacial contact performance between the metal and the 2D material, the fabricated device was subjected to vacuum (approximately 10 [missing information]). -3 Store under the specified conditions for 6 to 12 hours. Drain voltage (V) D 1004, Gate voltage (V) G ) 1005 and source ground 1006 are further shown in the figure Figure 10A The schematic diagram of device 1000 is shown.

[0283] Cross-sectional ADF-STEM and energy-dispersive X-ray spectroscopy (EDX) analyses were performed to obtain atomic-resolution images of the device and its components (for MoSe2, WSe2, and α-In2Se3, respectively). Figure 10B Images 1011-1013 in the image show a layered structure, a clean interface, and a uniform atomic distribution.

[0284] To verify the electrical properties of the synthesized material, transport and output curves were investigated. For MoSe2, the transport curves showed a conduction current when a positive gate bias was applied, regardless of the drain voltage. Figure 10C (each has V) D Curves 1021-1022 for 0.1 V and 1 V, with inset 1023 showing an optical image of the FET device. Furthermore, when the gate bias is positive, the output curves show a higher drain current (…). Figure 10F Each has V D The curves (1059, 1053, 1052, and 1051) for -40V, 20V, 30V, and 40V indicate its n-type characteristics. [Jung 2015]. Conversely, for WSe2, the transfer curves show on-current regardless of the drain voltage when a negative gate bias is applied. Figure 10D (each has V) D Curves 1031-1032 show the values ​​for 0.1 V and 1 V, with inset 933 showing an optical image of the FET device. Similarly, when the gate bias is negative, the output curve shows a higher current. Figure 10G Each has V D Curves (1063, 1065, 1066, 1067, 1068, and 1051) at 20V, 0V, -10V, -20V, -30V, and -40V respectively, show typical p-type characteristics. [Kim 2023]. This demonstrates that FWF technology can produce both n-type and p-type semiconductor wafers, achieving 1.1 × 10⁻⁶ for MoSe₂. 6 The on / off ratio and 6.81 cm 2 · V -1 · s -1 The mobility was 1.74 × 10⁻⁶. For WSe2, this was achieved. 4 The on / off ratio and 2.96 cm 2 · V -1 · s -1 migration rate.

[0285] In the case of α-In2Se3 ( Figure 10E Each has V DCurves 1041-1042 for 0.1 V and 1 V (with inset 1043 showing an optical image of the FET device) illustrate the on-current with a positive gate bias, which is typical n-type semiconductor behavior. However, due to the ferroelectric properties of α-In₂Se₃, the curve also exhibits a clockwise hysteresis loop. [Si 2019]. Further durability testing was conducted to observe the SET / RESET characteristics of α-In₂Se₃. During the durability test, the following sequence was repeated 1000 times: a gate voltage of -40 V with a pulse width of 1 s was applied to form a SET state, and the channel current was subsequently measured with a drain voltage of 1 V. Afterwards, a gate voltage of +40 V with a pulse width of 1 s was applied to form a RESET state, and the channel current was subsequently measured with a drain voltage of 1 V.

[0286] like Figure 10H As shown, when the on / off ratio is approximately 10 2 No performance degradation was observed after 1,000 cycles, indicating high durability comparable to that of α-In₂Se₃ grown by chemical vapor deposition [Si 2019]. The results demonstrate that materials produced by non-equilibrium FWF exhibit excellent electrical properties, which can facilitate the development of various devices with two-dimensional materials and promote fundamental research on these materials, which can now be readily obtained at gram levels at reduced costs (as further elaborated below).

[0287] A comparison was made between commercially available single-crystal α-In₂Se₃ and FWF α-In₂Se₃ to demonstrate the comparability of the properties between the two materials. Since the device geometry and pre- / post-processing must be identical for a valid comparison, the FWF α-In₂Se₃ device of this invention was compared with commercially available single-crystal α-In₂Se₃ (2DSemiconductors) fabricated under the same conditions. ® The devices were compared. With a positive gate bias, the output and transfer curves exhibited the expected higher drain current and clockwise hysteresis loop, as well as on-current, indicating ferroelectric n-type semiconductor performance. Durability tests were also performed, demonstrating SET / RESET characteristics. The transfer curves, output curves, and durability performance of the FWF material and commercially available single crystals were comparable when compared to FWF.

[0288] The previously reported work is summarized in Table II. Due to different geometries and manufacturing protocols, direct comparisons between the reported work and the devices disclosed and taught herein are unreliable for MoSe2, WSe2, and α-In2Se3. Therefore, it is necessary to provide a comparison of device performance between commercially available α-In2Se3 single crystals and our FWF α-In2Se3 to demonstrate electronic similarity.

[0289] Table II

[0290] Comparison of performance and device parameters between previously reported work and this paper.

[0291]

[0292] Tribology and coefficient of friction comparison

[0293] A comparative analysis of the coefficient of friction (COF) between commercially available MoSe2 and FWF MoSe2 was conducted to demonstrate superior and stable tribological properties. For tribological property measurements, samples were prepared by coating alumina substrates with commercial MoSe2 powder (Millipore-Sigma) and FWF MoSe2 powder. The powder was applied directly to the substrate and carefully spread by rubbing it on the surface in a circular motion for 5 minutes to disrupt inhomogeneities and achieve additive incorporation as a coating. To evaluate the tribological properties of the samples in sliding reciprocating motion, a tribometer with a ball-flat configuration was used. In this test, a 6 mm diameter chromium steel 52100 ball was slid across a rectangular flat alumina sample for 10 minutes under different load conditions (1 N, 5 N, and 10 N) at a frequency of 3 Hz. The COF change over time was measured and reported at a sampling rate of 100 data points per second. The mass of the coating was 0.2 g.

[0294] Figure 11A The time-dependent COF changes over 120,000 measurements are shown for reference alumina (fuzzy square 1101), commercial MoSe2 (fuzzy circle 1102), and FWF MoSe2 (fuzzy triangle 1103). Moving average trend lines for reference alumina (line 1104), commercial MoSe2 (line 1105), and FWF MoSe2 (line 1106) at 1 N are also shown. Figure 11A As shown, in the initial stage of the test, the COF of commercially available MoSe2 and FWF MoSe2 were virtually indistinguishable. However, after 2 minutes of operation, a significant increase in the COF of commercially available MoSe2 was observed.

[0295] Similarly, under different loads, FWF MoSe2 outperforms commercially available MoSe2. Figure 11B (For alumina, commercial MoSe2, and FWF MoSe2, see references 1011-1013). Under applied loads of 1 N, 5 N, and 10 N, the coefficient of friction showed reductions of 69%, 20%, and 41%, respectively. These results reveal that commercially available MoSe2 films degrade and / or wear at a faster rate than FWF MoSe2 films, indicating differences in the quality of the initial powder.

[0296] EDX analysis was performed on both flakes to investigate impurity concentrations. Neither material showed a significant impurity concentration, indicating that impurities are not the source of performance differences. The low concentration of oxygen impurities in FWF MoSe2 can be attributed to effective degassing. We developed a careful mathematical model to describe the behavior of oxygen defects in MoSe2 when exposed to the extreme heat generated during the FWF process.

[0297] To study degassing using density function theory (DFT) [Dudarev 1998], the formation energy of O substitution of Se in the MoSe2 crystal structure was calculated using the following equation:

[0298] (6)

[0299] in It is the total DFT energy of a 4×4 MoSe2 supercell in which two O atoms replace two Se atoms. It is the total number of MoSe2 units in the supercell. It is the DFT energy per unit cell in a defect-free MoSe2 crystal (layered structure, space group C1, lattice constants: a = b = 3.314 Å, c = 13.842 Å). It is the DFT energy of each Mo atom in the BCC crystal of Mo metal, and It is the DFT energy of a free O2 molecule.

[0300] The chemical potential of O2 gas as a function of pressure p and temperature T is calculated according to the following equation [Reuter 2001]:

[0301] (7)

[0302] in Entropy enthalpy Taken from thermochemical tables. [Chase 1975] .

[0303] DFT methods are used because they are implemented in the Vienna Ab initio Simulation Package (VASP) [Kresse 1996]. Plane wave extensions up to 500 eV are combined with all-electron projected enhanced wave (PAW) potentials [Blöchl 1994]. Exchange correlations are handled within the generalized gradient approximation (GGA) using functions parameterized by Perdew-Burke-Ernserhof [Perdew 1996]. Periodic conditions are applied to supercells or single crystals of crystal structures where the Brillouin zone integral converges to a Monkhorst-Pack type grid [Monkhorst 1976]. When optimizing structures using a conjugate gradient algorithm as implemented in VASP, both the positions of atoms and single cells are fully relaxed, such that the maximum force on each atom is less than 0.01 eV / Å.

[0304] The governing equation describes the formation energy of oxygen vacancies in MoSe2 relative to free oxygen molecules. This equation depends on internal pressure and temperature. Regardless of pressure, the free energy becomes positive around 2000 K, indicating that oxygen vacancies are effectively eliminated during synthesis. The subtle oxygen signal in EDX can be attributed to adsorbed air and possibly the formation of a self-limiting primary oxide layer.

[0305] The source of the difference between the two materials was demonstrated at the edge of the sheet, where commercially available MoSe2 showed an amorphous layer of about 10 nm thickness. Figure 12A-12B In contrast, FWF MoSe2 showed almost no amorphous edges, while ADF-STEM atomic resolution images revealed well-defined crystalline edges. Figure 12D-12E Selected area electron diffraction (SAED) patterns depict the presence of polycrystalline and amorphous components in commercial MoSe2. Figure 12C ), while single crystallinity was observed in FWF MoSe2 ( Figure 12F ).

[0306] This superior and stable performance is due to the single-crystal nature of FWF MoSe2, resulting in a lower overall coefficient of friction and enhanced tribological properties [Liu 2018; Lee 2010; Huang 2018]. Because FWF MoSe2 coated materials have a well-defined layered orientation, these sheets can easily slide against each other, thereby reducing motion resistance and thus lowering the coefficient of friction.

[0307] FWF's scalability

[0308] A key advantage of the FWF method is its scalability to gram-scale production without complexity. Such high scalability is rarely observed in laboratory chemical synthesis, which typically requires additional engineering, equipment setup, and / or alternative synthetic routes to ensure complete conversion of the material [Li 2021]. In contrast, FWF can be readily scaled up by adjusting the voltage to accommodate increases in reactant mass.

[0309] Furthermore, the semi-enclosed internal reactor allows for effective degassing, playing a crucial role in permitting the incorporation of highly volatile agents such as chalcogens. Additionally, degassing prevents oxygen permeation and the rupture of the internal tubing. As discussed and described above (WSe2-gram scale), the scalability of FWFs was demonstrated through the synthesis of WSe2 from W and Se precursors, and easy gram-scale production was successfully achieved. See also Figures 6A-6D . Figure 6A The synthesis of 1.11 g of WSe2 in a single reaction is shown. XRD analysis ( Figure 6B ) and X-ray photoelectron spectroscopy (XPS) spectroscopy ( Figures 6C-6D The results showed highly pure crystalline WSe2 with no identifiable byproducts or residues of the initial precursor. This representative gram-scale FWF synthesis of WSe2 reveals the significant scalability of the FWF process.

[0310] FWF Life Cycle Assessment (LCA)

[0311] Life cycle assessment (LCA) of nanomaterials and processes not yet industrialized can be challenging due to significant inhomogeneities in the field and the diversity of product categories. For example, TMDs can be synthesized using a variety of different methods, including modified chemical vapor transport (CVT) or deposition processes, as well as flux growth methods. To facilitate direct comparison of FWF methods, only synthetic methods that produce similar products are considered. Therefore, methods capable of producing single-crystal, multilayered, low-defect-density MoSe2 are considered, rather than methods producing single-layered, highly defective, or polycrystalline layers. For most TMDs that cannot be stripped from naturally occurring minerals such as MoS2 and WS2, very small production scales exist. Therefore, these other TMD products have high economic value but a small market size, largely limited to academic use. 100 g of small crystalline MoSe2 functional units are used, as this can be considered laboratory-scale and allows for comparisons between published synthetic methods while minimizing the impact of assumptions associated with hypothetical pilot-scale production. The FWF reaction pathway is compared with molten Mg autoclave reaction and CVT flux growth methods. It should be noted that CVT flux growth can grow larger crystals than the molten Mg and FWF reaction pathway.

[0312] A comprehensive life cycle assessment was conducted to compare the sustainability of FWF with Mg-assisted autoclave synthesis [Upadhyay 2021] and chemical vapor transport (CVT) methods [Ubaldini 2014] for the synthesis of 100 g of MoSe2. [Hellweg 2014] . These two methods were chosen because the end products exhibit similar properties, such as multilayering and high crystallinity. The cumulative energy demand from cradle to gate LCA (Cradle-to-Gate) is ( Figure 13A ), global warming potential ( Figure 13B ) and cumulative water consumption ( Figure 13C The LCA (Liquid Chemical Analysis) classifies MoSe2 into different components based on its composition. LCA indicates that, compared to autoclave and CVT methods, the FWF synthesis of MoSe2 uses 56%-83% less energy, produces 71%-94% less greenhouse gases, and consumes 90%-97% less water. Initial production costs (…) Figure 13D The results were provided by a technical and economic assessment (TEA). Preliminary TEA results indicate that even without the sale of flash-evaporated graphene, FWF offers significant cost savings in the preparation of inorganic materials, making it an attractive manufacturing option.

[0313] Applications and uses

[0314] The Joule heating technique (a non-equilibrium, ultrafast heat conduction method) can be used to prepare a wide variety of materials, including, for example, transition metal dichalcogenides (TMDs), Group XIV dichalcogenides, and other non-TMD materials, each completed within 5 seconds under ambient conditions. Compared to other synthetic methods, FWF offers significant advantages in terms of easily achievable gram-scale scalability and sustainable manufacturing standards. Furthermore, FWF allows for the production of phase-selective and single-crystal bulk powders, phenomena rarely observed by any other synthetic method. Moreover, FWF MoSe2 exhibits superior tribological properties compared to commercially available MoSe2, demonstrating the quality of FWF materials. The ability to atomically substitute and dope further illustrates the versatility of FWF as a general-purpose bulk inorganic material synthesis scheme. Therefore, the Joule heating technique advances inorganic material production while remaining environmentally conscious by providing sustainable manufacturing that prioritizes energy efficiency, minimal water consumption, scalability, and the ability to generate diverse materials.

[0315] Because no current flows directly through the material, FWF can also produce amorphous carbon (examples listed above). This is one of the main obstacles that FJH cannot achieve.

[0316] Therefore, embodiments of the present invention allow for the rapid synthesis of gram-scale crystalline transition metal dichalcogenides, which is typically not achievable simultaneously at this quality and speed. Industrially, this can be scaled up to kilogram and multi-kilogram scales in seconds per batch. The performance of cells using SnS2 as the anode has been successfully demonstrated. As shown, after three initial cycles, the capacity retention is almost 99%, which is a very high figure. Further optimization of the conductivity (e.g., doping) can improve cell performance, resulting in even higher capacities than graphite anodes.

[0317] The suitability of these products in semiconductor devices, and particularly in transistors, has been demonstrated.

[0318] The products manufactured using the process described in the embodiments of the present invention can also be used in other optical and electronic devices.

[0319] In some embodiments, pulse schemes for applying voltage pulses to control the flash Joule heating mechanism via controlled electronic modulation may be useful. Such pulse schemes may include variable frequency drive (VFD), pulse width modulation (PWM), proportional-integral-derivative (PID) control, three-term control, and combinations thereof. Such controlled electronic modulation is discussed in Tour'193 PCT application, the entire contents of which are incorporated herein by reference.

[0320] Therefore, the method of embodiments of the present invention is faster, more energy-efficient, and cheaper than other methods in the production of gram-scale transition metal dichalcogenides. The crystallinity of the product is comparable to that produced by chemical vapor deposition, which takes minutes to hours to complete.

[0321] These processes are also kinetically driven, rather than thermodynamically driven, allowing the formation of products that cannot be synthesized by many other methods. Compared to conventional flash Joule heating, this method allows for the formation of products that would normally not be formed.

[0322] While embodiments of the invention have been shown and described, modifications can be made thereto by those skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein and the examples provided herein are merely illustrative and not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. The scope of protection is not limited by the description set forth above, but only by the following claims, which include all equivalents of the subject matter of the claims.

[0323] All patents, patent applications and publications cited in this document are hereby incorporated in their entirety by reference to the extent that they provide illustrative, procedural or other details for the purposes set forth herein.

[0324] Quantities and other numerical data may be presented in range format herein. It should be understood that this range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the numerical values ​​explicitly stated as the limits of the range, but also all individual numerical values ​​or subranges encompassing that range, as if each numerical value and subrange were explicitly stated. For example, a numerical range of approximately 1 to approximately 4.5 should be interpreted not only to include the explicitly listed limits of 1 to approximately 4.5, but also to include individual numerical values ​​such as 2, 3, and 4, as well as subranges such as 1 to 3, 2 to 4, etc. The same principle applies to ranges listing only a single numerical value, such as “less than approximately 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0325] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the subject matter of this disclosure pertains. Although any methods, apparatus, and materials similar or equivalent to those described herein may be used in the practice or testing of the subject matter of this disclosure, representative methods, apparatus, and materials are described here.

[0326] According to long-standing patent law practice, the terms “a” and “an” are used in this application (including the claims) to mean “one or more”.

[0327] Unless otherwise specified, all figures used in this specification and claims to indicate quantities of components, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in this specification and appended claims are approximations that may vary depending on the desired properties sought to be obtained according to the subject matter disclosed herein.

[0328] As used herein, when referring to values ​​or amounts of mass, weight, time, volume, concentration, or percentage, the terms “about” and “substantially” are intended to cover variations of ±20% of a specific amount in some embodiments, ±10% of a specific amount in some embodiments, ±5% of a specific amount in some embodiments, ±1% of a specific amount in some embodiments, ±0.5% of a specific amount in some embodiments, and ±0.1% of a specific amount in some embodiments, as such variations are suitable for implementing the disclosed methods.

[0329] As used herein, the terms “substantially perpendicular” and “substantially parallel” are intended to cover the following variations: in some embodiments, within ±10° in the vertical and parallel directions, respectively; in some embodiments, within ±5° in the vertical and parallel directions, respectively; in some embodiments, within ±1° in the vertical and parallel directions, respectively; and in some embodiments, within ±0.5° in the vertical and parallel directions, respectively.

[0330] As used herein, the term “and / or” in the context of a list of entities means that the entities exist individually or in combination. Thus, for example, the phrase “A, B, C and / or D” includes not only A, B, C and D individually, but also any and all combinations and sub-combinations of A, B, C and D.

[0331] References

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Claims

1. A method comprising: (a) Providing internal raw materials within the internal container; (b) Providing external feedstock within an external container, wherein the internal container is located within the external container in the flash Joule heating apparatus; and (c) Applying one or more voltage pulses, alternating current (AC), direct current (DC), or a combination thereof across the external material to subject the external material to a flash Joule heating process, wherein the flash Joule heating process on the external material results in the internal material being converted into the converted material.

2. The method of claim 1, wherein the flash Joule heating process of the external raw material provides conductive heating and / or radiative heating to the internal raw material, causing the internal raw material to be transformed into the transformed material.

3. The method according to claim 1, wherein the transformed material is a two-dimensional material.

4. The method according to claim 1, wherein the converted material is selected from the group consisting of: FeS2, CoS2, CoS... x Se y , CoSe, NiS2, NiSe2, Cu9S5, NbSe2, MoSe2, TiSe2, In2Se3, SnS2, SnS x Se y ,SnSe2,WSe2,WS2,Bi2S3,Bi x S y Se z ,Bi2Se3,TiN,LaBO3,Cu2Se,Cu 0.87 Se and its combinations and mixtures.

5. The method of claim 1, wherein the converted material comprises chalcogenides, metals and / or alloys.

6. The method according to claim 1, wherein the external raw material is selected from the group consisting of: graphene, flash graphene, disordered graphene, anthracite, coconut shell-derived carbon, high-temperature treated biochar, activated carbon, calcined petroleum coke, metallurgical coke, coke, sub-graphite, carbon nanotubes, bituminous material, acetylene black, carbon black, ash, carbon fiber, graphite, and combinations and mixtures thereof.

7. The method of claim 1, wherein after the voltage pulse is applied across the external material to subject the external material to a flash Joule heating process, the external material is converted into flash graphene.

8. The method of claim 7, wherein the flash-evaporated graphene is reused multiple times as the external raw material in the method of claim 1.

9. The method of claim 7, further comprising: (a) Remove the converted material from the inner container; (b) Providing a second internal feedstock within the internal container; as well as (c) Apply one or more voltage pulses, AC, DC or a combination thereof across the flash graphene in the outer container to subject the flash graphene to a flash Joule heating process, wherein the flash Joule heating process on the flash graphene causes the second internal raw material to be converted into the second converted material.

10. The method of claim 9, wherein (a) The second internal raw material is a raw material of the same type as the internal raw material that is converted into the transformed material; and (b) The second converted material is of the same type as the converted material.

11. The method of claim 9, wherein (a) The second internal raw material is a raw material of a different type from the internal raw material that is converted into the transformed material; and (b) The second transformed material is of a different type from the transformed material.

12. The method of claim 1, wherein the step of applying the one or more voltage pulses utilizes a DC voltage.

13. The method of claim 1, wherein the step of applying the one or more voltage pulses utilizes pulsed DC.

14. The method of claim 1, wherein the step of applying the one or more voltage pulses utilizes an AC voltage.

15. The method of claim 1, wherein the step of applying the one or more voltage pulses utilizes a combination of DC voltage and AC voltage.

16. The method of claim 1, wherein (a) The step of applying the one or more voltage pulses, AC, DC, or a combination thereof includes controlling the flash Joule heating process by controlled electronic modulation, and (b) The controlled electronic modulation is generated by a group of control methods selected from variable frequency drive (VFD), pulse width modulation (PWM), proportional integral derivative (PID) control, three-term control and combinations thereof.

17. The method of claim 16, wherein the controlled electronic modulation utilizes (i) a DC current, (ii) a uniform non-traveling AC current, or (iii) a combination thereof.

18. The method of claim 1, further comprising applying an internal container current through the internal material when one or more voltage pulses, AC, DC or a combination thereof are applied across the external material.

19. An apparatus comprising: (a) An internal container operable to receive internal raw materials; (b) An external container operable to receive an external material, wherein the external container is (i) a non-conductive container operable to confine the external material or (ii) a conductive container operable to directly flash Joule heating; as well as (c) An electrode operable to apply a voltage pulse, alternating current (AC), direct current (DC), or a combination thereof across the external material confined within the external container to subject the external material to a flash Joule heating process, wherein the flash Joule heating process of the external material results in the internal material being transformed into the transformed material.

20. The device of claim 19, wherein the converted material is a two-dimensional material.

21. The apparatus of claim 19, wherein the converted material is selected from the group consisting of: FeS2, CoS2, CoS... x Se y , CoSe, NiS2, NiSe2, Cu9S5, NbSe2, MoSe2, TiSe2, In2Se3, SnS2, SnS x Se y ,SnSe2,WSe2,WS2,Bi2S3,Bi x S y Se z ,Bi2Se3,TiN,LaBO3,Cu2Se,Cu 0.87 Se and its combinations and mixtures.

22. The apparatus of claim 19, wherein the converted material comprises chalcogenides, metals and / or alloys.

23. The apparatus of claim 19, wherein the external raw material is selected from the group consisting of: graphene, flash graphene, disordered graphene, anthracite, coconut shell-derived carbon, high-temperature treated biochar, activated carbon, calcined petroleum coke, metallurgical coke, coke, sub-graphite, carbon nanotubes, pitchblende, acetylene black, carbon black, ash, carbon fiber, graphite, and combinations and mixtures thereof.

24. The apparatus of claim 19, wherein after applying the voltage pulse, AC, DC or a combination thereof across the external material to subject the external material to a flash Joule heating process, the external material is converted into flash graphene.

25. The apparatus of claim 19, further comprising a controller that controls the flash Joule heating process applied by the electrodes via controlled electronic modulation, wherein... (a) The controller is selected from a group consisting of a variable frequency drive (VFD) controller, a pulse width modulation (PWM) controller, a proportional integral derivative (PID) controller, a three-term controller, and combinations thereof.

26. The device of claim 19, wherein the controlled electronic modulation is operable using (i) a DC current, (ii) a uniform non-traveling AC current, or (iii) a combination thereof.

27. The device of claim 19, further comprising an internal container electrode operable to apply an internal container current through the internal material when one or more voltage pulses, AC, DC or a combination thereof are applied across the external material.

28. An apparatus comprising: (a) An internal container operable for receiving raw materials; (b) An external container that is operable to provide a protective atmosphere or vacuum for the resistance heater; (c) The resistance heater, which is located inside the outer container; (d) An electrode operable to supply AC or DC current to the resistance heater; as well as (e) A plug, which is located in the inner container to contain the raw material therein.

29. The device according to claim 28, wherein (a) The inner container is a transparent inner container; (b) The resistance heater is a tubular resistance heater; (c) The resistance heater is concentric within the outer container; and (c) The electrode is a tubular electrode.

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