Manufacturing method of Vanadium Dioxide using tetra arc melting method

Abstract

The present invention relates to a method for producing vanadium dioxide using a tetra-arc melting method. Unlike conventional methods that require complex wet processes, long-term high-temperature heat treatment, and multi-stage reduction conditions, this method provides vanadium dioxide with high crystallinity by concentrating electrical energy on a pellet during a short arc discharge time of within a few seconds. This highly crystallin VO₂ has an accurate phase transition temperature, making it effective for use in various applications such as smart windows, heat-blocking coatings, optical films, temperature sensors, thermal switching devices, and next-generation battery materials. Furthermore, the present invention is expected to be utilized across various industrial sites, as it enables the production of highly crystalline vanadium dioxide in a much shorter time compared to existing heat treatment-based technologies, despite its simple device configuration and low manufacturing costs.

Description

Technology Field

[0001] The present invention relates to a method for producing vanadium dioxide using a tetra-arc melting method, and more specifically, to a method for producing vanadium dioxide using a tetra-arc melting method that can produce a highly crystalline vanadium dioxide compound with only an arc discharge within a few seconds. Background Technology

[0003] Vanadium dioxide (VO2) is a representative vanadium oxide compound with metal-insulator phase transition characteristics, characterized by distinct changes in electrical and optical properties along with a phase transition at approximately 68°C. Based on these characteristics, vanadium dioxide is attracting attention as a material with very high potential for applications such as smart windows, visible light blocking films, thermal switching devices, infrared sensors, and electrode materials for next-generation secondary batteries.

[0004] Recently, various studies have been actively conducted to control the phase transition temperature of vanadium dioxide to suit actual usage purposes or to secure manufacturing technology for VO₂ single crystals or polycrystalline materials with high crystallinity. For example, as shown in Patent Document 1 below, a method for synthesizing vanadium dioxide nanoparticles has been proposed that includes a step of hydrothermal synthesis at a temperature of 210°C or higher and 240°C or lower. In another Patent Document 2, a technology for producing vanadium dioxide (VO₂) powder has been presented, which involves heating to 560 to 720°C in an electric furnace or a horizontal furnace and then maintaining the heating temperature for about 2 hours to partially reduce to vanadium dioxide (VO₂) powder.

[0005] However, these methods require complex wet processes and long-term high-temperature heat treatment, and there are limitations in stably producing highly crystalline VO₂ in a short period of time. Accordingly, the inventors have completed the present invention by developing a new vanadium dioxide manufacturing technology based on a tetra-arc melting method that can rapidly produce highly crystalline vanadium dioxide using only arc discharge within a few seconds, thereby replacing the existing manufacturing method based on long-term high-temperature heat treatment. Prior art literature

[0007] Korean Registered Patent Publication No. 10-2644689 “Method for Synthesizing Vanadium Dioxide Nanoparticles” Korean Registered Patent Publication No. 10-2344756 “Method for Partial Reduction of Vanadium Pentoxide Using Ammonia Solution and Vanadium Dioxide Powder Prepared Therefrom” The problem to be solved

[0008] Conventional methods for manufacturing vanadium dioxide have limitations in stably producing highly crystalline VO₂ in a short period of time, such as requiring long-term heating ranging from tens of minutes to several hours at high temperatures of 400°C or higher, or undergoing complex precursor preparation steps through wet processes.

[0009] Accordingly, the present invention aims to provide a new method for producing vanadium dioxide that can stably produce highly crystalline VO₂ compounds in a short time without performing high-temperature heat treatment for a long time or complex wet processes, as a solution to the problems described above.

[0010] In particular, the present invention aims to provide a method for producing vanadium dioxide that can precisely control the crystal phase and phase transition characteristics of VO₂ by directly melting it by arc discharge using a tetra-arc melting method and then cooling it. means of solving the problem

[0012] To achieve the above objective, the present invention provides a method for manufacturing vanadium dioxide using a tetra-arc melting method, characterized by comprising the steps of: compression molding a vanadium oxide compound to produce a pellet as a preferred embodiment of the present invention; loading the pellet into the central part of a mold provided on a lower support of a tetra-arc melting furnace; forming a vacuum inside the tetra-arc melting furnace and then supplying an inert gas; inducing an arc discharge on the loaded pellet to produce a molten material; and cooling the molten material to form a crystalline vanadium dioxide compound.

[0014] In addition, in the step of manufacturing the above molten material, the temperature of the mold provided on the lower support of the tetra arc melting furnace is characterized by being in the range of 700 to 1,150℃.

[0016] In addition, in the step of manufacturing the molten material, the arc discharge is characterized by applying a DC voltage of 30 to 40 V and a current of 20 to 30 A.

[0018] In addition, in the step of manufacturing the molten material, the arc discharge is characterized by being performed for 5 to 10 seconds.

[0020] In addition, the lower support (200) is characterized by the mold (620) rotating at a speed of 20 to 60 rpm in conjunction with the rotational action of the rotation shaft (900) by driving a rotary motor provided at the bottom of the tetra arc melting furnace. Effects of the invention

[0022] The present invention relates to a manufacturing method that can efficiently produce highly crystalline vanadium dioxide in a short period of time using a tetra-arc melting method. Unlike conventional methods that require complex wet processes, long-term high-temperature heat treatment, and multi-stage reduction conditions, this method has the effect of providing highly crystalline vanadium dioxide by concentrating electrical energy on a pellet during a short arc discharge time of within a few seconds.

[0023] This highly crystalline VO2 has an accurate phase transition temperature, making it effective for use in various applications such as smart windows, heat-blocking coatings, optical films, temperature sensors, thermal switching devices, and next-generation battery materials. In addition, the present invention has the effect of controlling the phase transition temperature or improving electrical and thermal stability by adding a dopant.

[0024] Furthermore, the present invention is expected to be utilized across various industrial sites, as it enables the production of highly crystalline vanadium dioxide in a much shorter time compared to existing heat treatment-based technologies, despite its simple device configuration and low manufacturing costs. Brief explanation of the drawing

[0026] FIG. 1 is a process block diagram for explaining a method for manufacturing vanadium dioxide according to a preferred embodiment of the present invention, and FIG. 2 is a schematic diagram illustrating a tetra-arc melting furnace apparatus for producing vanadium dioxide according to a preferred embodiment of the present invention, and FIG. 3 is a schematic diagram showing the state in which the melting chamber and the lower support of the tetra-arc melting furnace device of FIG. 2 are separated, and FIG. 4 is a schematic diagram showing the structure in which the mold and the shaft of the rotary motor of the tetra-arc melting furnace device of FIG. 2 are combined. FIG. 5 is a photograph of vanadium dioxide prepared according to a preferred embodiment of the present invention, and FIG. 6 is a DSC graph measuring vanadium dioxide prepared according to a preferred embodiment of the present invention, Figure 7 is an XRD graph of vanadium dioxide prepared according to a preferred embodiment of the present invention. Specific details for implementing the invention

[0027] The present invention will be described in detail below according to preferred embodiments with reference to the attached drawings, but specific descriptions of configurations and operations that are readily known to those skilled in the art will be omitted. Furthermore, it should be noted that the present invention is not necessarily limited by the following embodiments, and that those skilled in the art can make various modifications to the invention within the scope of the technical concept of the invention without departing from it.

[0029] A method for producing vanadium dioxide using a tetra-arc melting method according to another preferred embodiment of the present invention (hereinafter referred to as the "vanadium dioxide manufacturing method") comprises, as illustrated in FIG. 1, a step of producing a vanadium oxide compound by compression molding to form a pellet; a step of loading the pellet into the central part of a mold provided on a lower support of a tetra-arc melting furnace; a step of forming a vacuum inside the tetra-arc melting furnace and then supplying an inert gas; a step of producing a molten material by inducing an arc discharge on the loaded pellet; and a step of cooling the molten material to form a crystalline vanadium dioxide compound.

[0031] First, the step of manufacturing a pellet by compression molding a vanadium oxide compound is a step of molding vanadium pentoxide (V2O5) into a pellet shape, and is a step of producing a specimen that has been pelletized by compressing vanadium pentoxide (V2O5) using a hydraulic press at a pressure of 10 to 30 MPa for 2 to 10 minutes.

[0032] The above pellets may have a diameter of 8 mm to 15 mm, but are not limited thereto.

[0034] Meanwhile, the vanadium oxide compound may further include one or more first dopants selected from the group consisting of aluminum (Al), magnesium (Mg), cerium (Ce), hafnium (Hf), zirconium (Zr), and silicon (Si).

[0035] Alternatively, the vanadium oxide compound may further include one or more second dopants selected from the group consisting of tungsten (W), molybdenum (Mo), niobium (Nb), and tantalum (Ta).

[0036] The vanadium oxide compound may be mixed with the first dopant or the second dopant in a molar ratio of 1:0.1 to 10, and then the vanadium oxide compound containing the dopant may be compression molded to produce pellets.

[0037] Through this, the phase transition temperature of vanadium dioxide (VO₂) can be controlled by inserting the first dopant or the second dopant into the vanadium oxide crystal lattice, and a specific crystalline phase of vanadium dioxide with improved electrical properties can be realized, thereby securing a crystalline vanadium dioxide compound that is highly useful for realizing secondary batteries.

[0039] Next, the step of loading the pellet into the center of the mold provided on the lower support of the tetra arc melting furnace is to separate the melting chamber (100) from the lower support (200) of the tetra arc melting furnace and then load the vanadium pentoxide (V2O5) pellet into the center of the mold (620) provided on the lower support (200).

[0041] Next, the step of supplying an inert gas after forming a vacuum inside the tetra arc melting furnace is to form a vacuum in the chamber internal space (S) by exhausting the air inside the chamber to the outside to lower the pressure in the chamber internal space (S) and then injecting an inert gas into the chamber internal space (S) with the lowered pressure.

[0043] Specifically, an O-ring (300) may be installed between the melting chamber (100) and the lower support (200) to seal the surface of the area where the melting chamber (100) and the lower support (200) meet so that external air does not enter the interior when the space (S) is formed into a vacuum.

[0045] At this time, if a large amount of air is present in the internal space (S) of the chamber, the pressure inside the chamber is 1×10⁻⁶ to prevent peroxidation reactions caused by air. -3 ~ 5×10 -3 Air can be expelled to the outside using a vacuum pump to lower the pressure to the torr level.

[0047] Next, as a step of injecting an inert gas into the space (S) inside the chamber where the pressure has been lowered, the inert gas can be injected until the pressure inside the chamber reaches 5 to 10 torr.

[0049] The above steps of exhausting air from inside the chamber to the outside (P300) and injecting inert gas into the chamber (P400) can be repeated 3 to 4 times.

[0051] Therefore, by removing as much oxygen from the air remaining in the chamber internal space (S) as possible, in addition to the vanadium dioxide (VO2) to be manufactured when vanadium (V) is exposed to an oxidizing atmosphere with excess oxygen, V₂O₃, V₆O₅ 13 The purpose is to prevent potential problems that could arise from the formation of other vanadium oxide compounds, such as those mentioned above.

[0053] In the present invention, one or more inert gases can be selected and used from argon (Ar), helium (He), or neon (Ne).

[0055] The step of manufacturing a molten material by inducing an arc discharge in the loaded pellets involves applying power to the tungsten electrode part and melting the pellets loaded in the center of the mold (620), which is the location where the arc discharge is concentrated, by the arc discharge output, to produce vanadium dioxide (VO₂). 2As a step of manufacturing the ) four tungsten electrode parts (410) can be brought near the pellet using an electrode control part (420), and then an arc discharge can be performed by applying power under constant current and voltage conditions.

[0057] It is preferable that the applied voltage is 30 to 40 V and the applied current is 20 to 30 A.

[0058] If the voltage and current intensity during arc discharge falls below the range specified above, there is a risk that the V₂O₅ pellets will not be sufficiently melted, and if they exceed the range specified above, there is a risk that the discharge will occur to other auxiliary parts connected to the electrode.

[0060] The above arc discharge may be performed for 5 to 10 seconds. By rapidly transferring high-temperature localized energy to the pellet with such a short discharge time to induce melting, the process time can be drastically shortened compared to conventional heat treatment methods that require more than a few minutes. In addition, it has the effect of suppressing unnecessary oxidation reactions, thereby stably securing the purity and phase transition characteristics of crystalline vanadium dioxide.

[0062] The temperature of the mold provided on the lower support of the tetra arc melting furnace may be in the range of 700 to 1,150°C. If the temperature of the mold is below this range, the pellets may not be sufficiently preheated, and cracking or non-homogeneous melting may occur due to thermal shock during arc discharge. If the temperature exceeds this range, there is a risk that vanadium dioxide (VO2) may be exposed to excessive heat and transition to other phases such as V2O3 and V2O5.

[0064] At this time, after confirming that an arc discharge is occurring, the mold (620) can be rotated at a speed of 20 to 60 rpm in conjunction with the rotational action of the rotating shaft (900) by driving the rotating motor provided at the bottom of the tetra arc melting furnace to uniformly melt the V2O5 pellets.

[0065] If the rotational speed of the mold (620) above is less than the range specified above, there is a risk that the pellets will not be melted uniformly, and if the rotational speed exceeds the range specified above, there is a risk that the molten material will be scattered inside the melting chamber (10) due to the centrifugal force of rotation.

[0067] The step of cooling the above molten material to form a crystalline vanadium dioxide compound may be a step of forming crystalline vanadium dioxide (VO₂) by turning off the output current and cooling it in a temperature range of 20 to 25 ℃ after the V₂O₅ pellet is completely melted by arc discharge.

[0069] Unlike the conventional growth method, which makes it difficult to produce vanadium dioxide compounds that form various phases, the present invention has the effect of producing crystalline vanadium dioxide (VO2) with excellent cell efficiency and conductivity by using a tetra arc melting furnace to produce vanadium oxide compounds according to arc generation conditions and inert gas partial pressure.

[0071] The present invention has the effect of stably producing crystalline vanadium dioxide (VO2) with excellent cell efficiency and conductivity by using a tetra arc melting furnace to control arc generation conditions and inert gas partial pressure, despite the characteristics of vanadium oxide, which makes it difficult to stably form various phases in conventional processes, through the vanadium dioxide (VO2) manufacturing method described above.

[0073] Meanwhile, a method for producing vanadium dioxide using a tetra arc melting method according to a preferred embodiment of the present invention (hereinafter referred to as a "vanadium dioxide manufacturing apparatus") is a tetra arc melting furnace having a structure as shown in FIGS. 2 to 4, specifically comprising: a melting chamber (100) in which a space (S) is formed in which vanadium oxide compound pellets are melted by an arc discharge output from a plurality of tungsten electrode parts (410); a lower support (200) on which a cylindrical mold for loading the vanadium oxide compound pellets is mounted; and an O-ring (300) mounted to seal the surface of the periphery where the melting chamber (100) and the lower support (200) meet so that external air does not flow into the interior when the space (S) is formed into a vacuum state.

[0075] The melting chamber (100) has a hemispherical structure in which the lower surface is open along the inner periphery to form a space (S) inside, and a plurality of tungsten electrodes (410) are mounted through the wall of the melting chamber as a means for arc discharge.

[0077] The above tungsten electrode part (410) is provided with an electrode control part (420) integrally coupled to the upper part so as to be rotatable, so by rotating the electrode control part (420), the tungsten electrode (410) can be moved in the forward and backward directions of the electrode, and thus it is also possible to adjust the position of the electrode.

[0079] In the present invention, it is preferable that the number of tungsten electrode parts (410) installed in the melting chamber (100) be four, and by applying a tetra-arc system, the energy of the arc discharge is uniformly transferred to the entire pellet, thereby improving the uniformity of the melting and crystal growth process of the vanadium oxide compound.

[0081] Additionally, the melting chamber (100) is provided with an air outlet (510) on one side for discharging air to the outside to form a vacuum inside the space (S); and an inert gas injector (520) for injecting inert gas into the internal space (S).

[0083] In addition, the melting chamber (100) is equipped with a viewport (800) for observing the space (S) inside the chamber, so that the state of the arc discharge output from the tungsten electrode part (410) and the melting process of the vanadium oxide compound pellet can be directly observed visually inside the space (S) of the melting chamber (100).

[0085] The lower support (200) is formed as a cylindrical structure with an upper surface open along the inner periphery and corresponding to the lower surface of the melting chamber (100), and includes a disc-shaped mold base plate (610) with a concave groove formed in the center, and a cylindrical mold (620) mounted in the concave groove and having the pellet loaded on its upper surface.

[0087] Additionally, it is preferable that the mold (620) has a structure in which a concave bowl-shaped groove (621) is formed on the upper surface so that the pellets can be loaded.

[0089] It is preferable to use copper material, which has high electrical conductivity and high thermal conductivity, for the above mold base plate (610) and mold (620).

[0091] For reference, the specifications of the mold (620) applied to the vanadium dioxide manufacturing apparatus used in the preferred embodiment of the present invention are a height of 10 to 30 mm and a diameter of 30 mm, and a structure in which a concave groove (621) is formed in the shape of a bowl with a diameter of 25.54 mm and a depth of 3 to 4 mm on the upper surface, and the structure is replaceable so that a mold of different heights can be used depending on the height of the material.

[0093] In conventional vanadium dioxide manufacturing devices using a tetra arc melting furnace, when performing the melting operation of the vanadium oxide compound pellets, the arc discharge does not occur toward the pellets but is discharged toward the copper plate at the bottom or the tungsten rod used for pulling. However, in order to solve the above problem, the present invention can adjust the height of the position where the pellets are loaded by installing an additional mold (620) in the center of the mold support plate (610) at the bottom.

[0095] And the lower support (200) is equipped with a cooling water tank (700) inside to cool the mold (620) heated by the molten pellets melted by arc discharge, and the cooling water (W) introduced through the cooling water inlet (710) comes into direct contact with the heated mold support plate (610) to cool the mold (620) through the mold support plate (610), which is made of copper material with high thermal conductivity, and the heated cooling water (W) is discharged to the outside through the cooling water outlet (720).

[0097] In addition, the mold base plate (610) can move up and down with the lower water-cooled copper plate, and at this time, an additional cylindrical mold (620) that can be detached is attached to the central part of the mold base plate (610), so that the distance between the sample and the electrode can be adjusted by adjusting the height of the mounted copper plate.

[0099] In addition, the lower support (200) is driven by a rotary motor (not shown in the drawing) located at the bottom to rotate the lower cylindrical mold (620) in conjunction with the rotation of the rotation shaft (900), thereby enabling the synthesis of a uniform material through the rotation of the pellet.

[0101] The above-mentioned pellet can be loaded in a tetra arc melting furnace with a structure as shown in FIG. 2, as shown in FIG. 3, by separating the melting chamber (100) from the lower support (200), and then loading the pellet so that the arc rods of the four tungsten electrodes (410) do not directly contact the pellet in the center of the upper surface of the cylindrical mold (620). Then, to seal the surface of the periphery where the melting chamber (100) and the lower support (200) meet so that external air does not enter when the space (S) is formed into a vacuum state, an O-ring (300) is installed and sealed. After that, to form a vacuum in the internal space (S) of the tetra arc melting furnace chamber, air is discharged from the space (S) using a vacuum pump, and after 20 minutes, when the vacuum is maintained to a certain level, an inert gas is introduced to create an atmosphere that suppresses the oxidation reaction. After that, an arc discharge is generated to melt the pellets, and a crystalline vanadium dioxide (VO2) compound can be produced through a cooling process.

[0103] As such, the vanadium dioxide manufacturing apparatus using the tetra arc melting method according to the present invention is a method that can reach a high temperature in a short time through arc discharge between the electrodes and the material by flowing a high current through four electrode parts. Since the arc discharge occurs locally, crystal growth is possible using only copper, which allows for cooling of the crucible, so there are no restrictions on the crucible. Furthermore, because the material can be melted quickly through high current, there is almost no vaporization and the growth time is short, so it is expected to be widely applied in future industrial applications.

[0105] Hereinafter, a method for producing vanadium dioxide using the tetra-arc melting method according to the present invention will be specifically explained through the following examples, and the present invention is not necessarily limited only to the following examples.

[0107] 1. Preparation of vanadium dioxide

[0109] (Example 1)

[0110] Vanadium pentoxide (V2O5) (98.4 wt%) was compressed using a hydraulic press at a pressure of 20 MPa for 5 minutes to produce pellets with a diameter of 12 mm. The pellets were placed in a tetra arc melting furnace with a structure as shown in FIG. 2. As shown in FIG. 3, the melting chamber was separated from the lower support, and the pellets were loaded into the center of the upper surface of a disc-shaped mold such that the arc rods of the four tungsten electrodes did not come into direct contact with the pellets. At this time, an O-ring was installed to seal the space between the lower support and the melting chamber. Then, to create a vacuum in the internal space (S) of the tetra arc melting furnace chamber, the pressure in the space (S) was set to 1×10 -3 Air was exhausted to the outside using a vacuum pump until it reached torr, and after 20 minutes, when it was maintained to the next constant vacuum, an inert gas Ar was introduced using a gas mass flow meter (MFC) to maintain the pressure of the inert gas Ar at 9 torr, thereby creating an arc discharge reaction atmosphere.

[0111] Then, a DC voltage of 30 V and a current of 20 A were applied to generate an arc discharge for 5 seconds. At this time, the mold was rotated at a speed of 30 rpm by driving a rotary motor to uniformly melt the pellets. Through this, the molten pellets were cooled to produce a crystalline vanadium dioxide (VO₂) compound.

[0112] For reference, Fig. 5 is a photograph showing the appearance of vanadium dioxide (VO₂).

[0114] (Examples 2 to 6)

[0115] Vanadium dioxide (VO₂) compounds were prepared in the same manner as in Example 1 above, but with different applied time conditions, applied voltage, and applied current during the arc discharge as shown in Table 1 below.

[0117] division Arc authorization time (seconds) Applied voltage (V) Applied current (A) Mold temperature (°C) 1 in implementation 5 30 20 700 2 in implementation 6 32 22 850 3 in implementation 7 35 25 950 4 in implementation 8 38 28 1,050 5 in implementation 9 40 30 1,100 6 in implementation 10 40 30 1,150

[0119] (Comparison Example 1)

[0120] 250 g of vanadium pentoxide (V2O5) (98.4 wt%) was leached with 1.7 L of 2 M NaOH solution at 60°C for 4 hours, and then separated by filtration. Subsequently, 294 g of NH4Cl was added and reacted at 25°C for 4 hours to produce the intermediate ammonium vanadate (NH4VO3). 30 g of the NH4VO3 was loaded into an alumina crucible, placed into a vacuum induction furnace inside a heater, and maintained under reduced pressure of 0.017 atm in an argon atmosphere. Afterward, the mixture was heated and maintained at 400°C for 60 minutes, then cooled to below 100°C under vacuum, and vanadium dioxide (VO2) powder produced in the alumina crucible was obtained.

[0122] 2. Evaluation of Vanadium Dioxide

[0123] DSC analysis was performed to analyze the phase transition characteristics of vanadium dioxide (VO₂) prepared through Example 1 above. Heat flow was measured while raising or lowering the temperature in a temperature range from -20°C to about 80°C.

[0124] As a result of the measurement, as shown in Fig. 6, VO2 exhibited a maximum endothermic peak at approximately 67.0°C when the temperature increased, and the latent heat was measured to be 40 J / g (187 kJ / L). When the temperature decreased, it showed a maximum exothermic peak at approximately 59.6°C, and the latent heat was confirmed to be 41 J / g (192 kJ / L). The hysteresis loop, which is the temperature difference between the two phase transition regions, was measured to be approximately 7.4°C, confirming that VO2 has reversible metal-insulating phase transition characteristics.

[0126] Meanwhile, in order to confirm the crystal structure of VO₂, the XRD (X'pert) of vanadium dioxide (VO₂) prepared through Example 1 above 3 The diffraction pattern was measured using a Cu target.

[0127] As indicated by the major diffraction peaks in Fig. 7 from the XRD analysis results, it can be seen that the vanadium dioxide prepared through Example 1 is a highly crystalline compound having a monoclinic crystal structure (M1 phase). In particular, the high resolution and strong diffraction intensity of the overall XRD peaks indicate different vanadium oxide phases (V2O3, V6O 13 This means that (e.g., V2O5) are not present. As such, it has been confirmed that the vanadium dioxide manufacturing method according to the present invention can efficiently synthesize highly crystalline monoclinic VO2 in a short period of time.

[0129] Although a method for producing vanadium dioxide using the tetra-arc melting method according to a preferred embodiment of the present invention as described above has been explained, this is merely an example and those skilled in the art will understand that various changes and modifications are possible within the scope of the technical spirit of the present invention. Explanation of the symbols

[0131] 100 : Dissolution Chamber 200 : Lower support 300 : O-ring 410 : Tungsten electrode part 420 : Electrode control unit 510: Air outlet 520: Inert gas inlet 610: Mold base plate 620 : Mold 700 : Cooling tank 710: Coolant inlet 720: Coolant outlet 800 : Viewport 900 : Rotation axis M: Pellet S: Space W: Coolant

Claims

Claim 1 The method is characterized by comprising the steps of: manufacturing a vanadium oxide compound into pellets by compression molding; loading the pellets into the central part of a mold provided on a lower support of a tetra-arc melting furnace; forming a vacuum inside the tetra-arc melting furnace and then supplying an inert gas; inducing an arc discharge on the loaded pellets to produce a molten material; and cooling the molten material to form a crystalline vanadium dioxide compound. The above lower support is, Characterized by the mold rotating at a speed of 20 to 60 rpm in conjunction with the rotational action of the rotating shaft by driving a rotary motor provided at the bottom of the tetra arc melting furnace. Method for producing vanadium dioxide using the tetra-arc dissolution method Claim 2 A method for producing vanadium dioxide using a tetra-arc melting method, wherein, in the step of producing the molten material according to claim 1, the temperature of the mold provided on the lower support of the tetra-arc melting furnace is in the range of 700 to 1,150℃. Claim 3 A method for producing vanadium dioxide using a tetra-arc melting method, wherein, in the step of producing the molten material according to claim 1, the arc discharge is characterized by applying a DC voltage of 30 to 40 V and a current of 20 to 30 A. Claim 4 A method for producing vanadium dioxide using a tetra-arc melting method, wherein, in the step of producing the molten material according to claim 1, the arc discharge is performed for 5 to 10 seconds. Claim 5 delete

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