TW202016025A - Method of producing vanadium dioxide - Google Patents

Abstract

The method for producing vanadium dioxide includes a raw material mixing step for mixing divanadium pentoxide and a carbon material source and obtaining a raw material mixture, a firing step for firing the raw material mixture at from 340 DEG C to less than 370 DEG C in an inert gas atmosphere to obtain a fired body, and a cooling step for cooling the fired body to room temperature; in the raw material mixing step, the molar ratio (C/V) of carbon atoms in the carbon material source to vanadium atoms in the divanadium pentoxide is 2.2 or higher, and the cooling step includes an oxidation treatment step for switching from an inert gas atmosphere to an oxygen-containing atmosphere during cooling.

Description

Manufacturing method of vanadium dioxide

The present invention relates to a method for producing vanadium dioxide which is useful as a thermochromic material or the like.

Thermochromic materials are materials that have the property of reversibly changing optical properties according to temperature, and the development of films or glasses that utilize this property is advancing. For example, in the case where thermochromic materials are used for window glass, sunlight can be reflected to block heat in summer, and sunlight can be used to pass heat in winter, so energy-saving technologies using thermochromic materials are subject to attention.

As a thermochromic material, vanadium dioxide is known. Regarding vanadium dioxide, it shows a monoclinic crystal structure below the phase transition temperature and has semiconductor properties. On the other hand, above the phase transition temperature, the crystal structure of the rutile type changes, showing metallic properties. Along with this phase transition, the resistance of vanadium dioxide or the transmittance in the infrared region greatly changes. In the case of applying a thermochromic material of vanadium dioxide to a window, in addition to the thermochromic properties, transparency is also required, and the particle size needs to be nano order.

As a method of manufacturing the nano-level vanadium dioxide, for example, a method of pulverizing a material obtained by melting vanadium oxide and tungsten oxide by a bead mill (refer to Patent Document 1); using hydrogen peroxide After oxidizing the vanadium oxide compound, a porous vanadium oxide is precipitated at a predetermined temperature, crushed, and then subjected to a reduction treatment (see Patent Document 2), etc. However, the methods described in Patent Document 1 and Patent Document 2 require complicated steps, which is industrially disadvantageous.

In addition, a method for producing vanadium dioxide by hydrothermal synthesis has also been proposed (for example, refer to Patent Document 3 and Patent Document 4), but it is expected to develop an industrially advantageous method considering energy saving, cost saving, environmental concerns, etc. .

In addition, as a method for producing vanadium dioxide, which is particularly useful as a heat storage agent, the inventors previously proposed a method of preparing a raw material mixed liquid containing vanadium pentoxide and an organic acid and spray-drying the raw material mixed liquid After processing to obtain a reaction precursor, it is calcined at 600°C to 900°C (see Patent Document 5). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2000-233929 [Patent Document 2] Japanese Patent Laid-Open No. 2011-136873 [Patent Document 3] Japanese Patent Laid-Open No. 2017-186398 [Patent Document 4] Japanese Patent Laid-Open No. 2017-110144 [Patent Document 5] Japanese Patent Laid-Open No. 2017-132677

[Problems to be solved by the invention]

However, according to the method of Patent Document 5, there is a problem that the calcination temperature is high and it is difficult to produce nanometer-level vanadium dioxide.

Therefore, an object of the present invention is to provide a method for producing vanadium dioxide, which is useful as a thermochromic material and has an average primary particle diameter of nanometer grade, by an industrially advantageous method. [Means to solve the problem]

In view of the actual situation, the inventors conducted diligent research and found that: in the method of obtaining a raw material mixture by mixing vanadium pentoxide with a carbon material source, and calcining the raw material mixture in an inert gas environment, if If the carbon material source as the reducing agent is excessive and calcined in the low temperature range of a specific temperature range, a calcined body containing vanadium oxide compounds such as V ₅ O ₉ and V ₄ O ₇ is obtained; During the cooling process of the vanadium oxide compounds such as V ₅ O ₉ and V ₄ O ₇ , the inert gas environment is switched to the oxygen-containing environment for oxidation treatment, which can convert the vanadium oxide compounds such as V ₅ O ₉ and V ₄ O ₇ into Monoclinic vanadium dioxide; in addition, the vanadium dioxide obtained in the above-mentioned manner has a primary particle size of nano-level, and nano-level particles can be obtained by disintegration or crushing, thus completing the present invention .

That is, the present invention is a method for manufacturing vanadium dioxide, which is characterized by comprising: a raw material mixing step, mixing vanadium pentoxide with a carbon material source to obtain a raw material mixture; a calcination step, placing the raw material mixture in an inert gas environment Calcining at 340°C or higher and less than 370°C to obtain a calcined body; and a cooling step to cool the calcined body to room temperature, wherein in the raw material mixing step, the carbon atoms in the carbon material source are relative to pentoxide The molar ratio (C/V) of vanadium atoms in divanadium is 2.2 or more. The cooling step includes an oxidation treatment step, and the inert gas environment is switched to an oxygen-containing environment during cooling. [Effect of invention]

According to the present invention, vanadium dioxide, which is useful as a thermochromic material and has an average particle diameter of primary particles of nanometer grade, can be produced by an industrially advantageous method.

Hereinafter, the present invention will be described based on its preferred embodiments.

<Raw material mixing step> The raw material mixing step of the present invention is a step of mixing vanadium pentoxide with a carbon material source to prepare a raw material mixture.

Examples of the carbon material source used in the raw material mixing step include: a material containing only carbon atoms; or a material that is thermally decomposed to generate carbon by calcination in a calcination step described later. Examples of specific carbon material sources include carbon materials and organic compounds having hydroxyl groups.

Examples of the carbon material include carbon black, carbon fiber, graphite, and activated carbon. Carbon black is not limited by which manufacturing method is used, and examples include furnace black obtained by furnace method, channel black obtained by channel method, and acetylene obtained by acetylene method. Black, thermal carbon black obtained by thermal method, etc. Examples of the carbon fiber include polyacrylonitrile-based carbon fiber and pitch-based carbon fiber.

Examples of the organic compound having a hydroxyl group include sugars, polyols, and organic acids.

Examples of sugars include monosaccharides such as fructose; disaccharides such as sucrose and lactose; oligosaccharides in which monosaccharides are bonded with about 3 to 20 molecules; polysaccharides such as starch and cellulose; xylitol and sorbitol Such as sugar alcohols.

Examples of the polyhydric alcohols include divalent alcohols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; trivalent alcohols such as glycerin and trimethylolpropane; Tetravalent or higher alcohols having 4 or more hydroxyl groups in the molecule; polymers having multiple hydroxyl groups such as polyvinyl alcohol.

Examples of organic acids include monocarboxylic acids such as formic acid, acetic acid, glycolic acid, lactic acid, and gluconic acid; dicarboxylic acids such as oxalic acid, maleic acid, malonic acid, malic acid, tartaric acid, and succinic acid; and the number of carboxyl groups The number 3 is carboxylic acid such as citric acid.

Among these organic compounds having a hydroxyl group, from the viewpoint that the vanadium pentoxide can be easily reduced, and when the wet mixing treatment is performed as described later, the vanadium pentoxide can be dissolved in an aqueous solvent. Organic acids.

In the raw material mixing step, it is important that the molar ratio (C/V) of carbon atoms in the carbon material source to vanadium atoms in vanadium pentoxide is 2.2 or more. The reason is that if the carbon material source for reducing vanadium pentoxide is less than the above-mentioned amount, a raw material mixture with excellent reactivity cannot be obtained, and when calcination is performed at a calcination temperature described later, the vanadium pentoxide used as a raw material does not react. Survival. In addition, the unreacted carbon material source may directly remain in the target vanadium dioxide. Therefore, from the viewpoint of obtaining high-purity vanadium dioxide, the carbon atoms in the carbon material source are different from those in the vanadium pentoxide. The molar ratio (C/V) of vanadium atoms is preferably 2.2 to 4.5, and more preferably 2.4 to 4.0.

The mixing of vanadium pentoxide and the carbon material source can be performed wet or dry. In the case of using an organic acid as the carbon material source, from the viewpoint of forming a raw material mixture with excellent reactivity, the raw material mixture is particularly preferably the following: Vanadium pentoxide and organic acid are mixed in an aqueous solvent to obtain a raw material dissolving solution in which each raw material is dissolved (hereinafter, sometimes referred to as "raw material dissolving step"), followed by a step of spray drying the raw material dissolving solution ( Hereinafter, sometimes referred to as "spray drying step").

Hereinafter, a preferred raw material mixing procedure will be described. In the raw material dissolving step, from the viewpoint of completely dissolving each raw material, the addition amount of vanadium pentoxide is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass relative to 100 parts by mass of the water solvent. Quality parts. In addition, in terms of high ability to dissolve vanadium pentoxide, the organic acid used in the raw material dissolving step is preferably carboxylic acid, and more preferably oxalic acid. In addition, in the raw material dissolving step, from the viewpoint of economy, the molar ratio (C/V) of carbon atoms in organic acids to vanadium atoms in vanadium pentoxide is preferably 2.2 to 4.5, Furthermore, it is preferably set to 2.4 to 4.0.

The dissolution temperature of the raw material dissolution step is not particularly limited, but from an industrially advantageous point of view, it is preferably 15°C to 100°C, preferably 20°C to 60°C.

The spray drying step is a step of spray drying the raw material solution prepared in the raw material dissolving step to obtain a raw material mixture. The raw material mixture obtained by spray drying is prepared by uniformly mixing each raw material at a molecular level, and has excellent reactivity.

In the spray drying method, the raw material solution is atomized by a predetermined method to dry the fine droplets produced thereby, thereby obtaining a raw material mixture. For atomizing the raw material solution, there are a method using a rotating disk and a method using a pressure nozzle. Either method can be used in the spray drying step.

In the spray drying method, the size of the droplets of the atomized raw material solution affects stable drying or the properties of the obtained dry powder. In detail, if the size of the raw material particles of the pulverized product relative to the size of the droplet is too small, the droplet becomes unstable, and it is difficult to smoothly dry it. From this viewpoint, the droplet size of the atomized raw material solution is preferably 1 μm to 50 μm, and more preferably 3 μm to 30 μm. The supply amount of the raw material dissolving liquid to the spray drying device is desirably determined in consideration of this viewpoint.

In addition, in terms of preventing the powder from absorbing moisture and easily recovering the powder, the drying temperature of the spray drying device is preferably such that the hot air inlet temperature becomes 180°C to 300°C, preferably 200°C to 250°C The adjustment is performed so that the hot air outlet temperature becomes 100°C to 200°C, preferably 105°C to 150°C.

In addition, for the purpose of changing the phase transition temperature of vanadium dioxide, auxiliary component elements may be added to the raw material mixture.

As the subcomponent element, one or two or more kinds selected from the group of Cr, W, Mo, Nb, Ta, Os, Ir, Ru, and Re are preferable. The auxiliary component element may be the auxiliary component element itself, or may be a compound containing the auxiliary component element. Examples of the compound containing the auxiliary component element include oxides of the auxiliary component elements, metal acids such as molybdic acid and tungstic acid, metal salts or ammonium salts thereof, alcoholates of the auxiliary component elements or auxiliary component elements Organic acid salts. The auxiliary component elements can be added to the raw material mixture in the form of solution, suspension or powder. In addition, when the raw material dissolving step is included, it is sufficient to mix vanadium pentoxide, organic acid, and auxiliary component elements in an aqueous solvent.

The added amount of the auxiliary component element is preferably adjusted appropriately according to the composition of vanadium dioxide represented by the general formula (1) described later.

In addition, the raw material mixture obtained in the raw material mixing step may be in an amorphous state or a crystalline state. From the viewpoint of forming a raw material mixture having excellent composition uniformity and excellent reactivity, it is preferable It is in an amorphous state.

In addition, the raw material mixture may be a reaction product of vanadium pentoxide and a carbon material source, or a reaction product of vanadium pentoxide and a carbon material source, and auxiliary component elements added as needed.

<Calcination step> The calcination step is a step of calcining the raw material mixture obtained in the raw material mixing step at a predetermined temperature in an inert gas environment to obtain a calcined body.

In the calcination step, calcination is performed at a lower temperature than in Patent Document 5, whereby the grain growth of the obtained calcined body can be suppressed, and finally vanadium dioxide having an average primary particle size of nanometer grade can be obtained.

It is important that the calcination temperature in the calcination step is 340°C or higher and less than 370°C. By calcining in this temperature range, a calcined body containing V ₅ O ₉ and/or V ₄ O ₇ (hereinafter, sometimes referred to as “vanadium oxide compound”) as a main component can be obtained. It can be converted into monoclinic vanadium dioxide by performing the oxidation treatment described below. From the viewpoint of obtaining higher purity monoclinic vanadium dioxide during X-ray diffraction analysis, the calcination temperature is preferably 340°C or higher and 365°C or lower. The calcination time is not particularly limited, but it is usually 1 hour or more, preferably 2 hours to 30 hours, and a satisfactory calcined body can be obtained.

Examples of usable inert gases include nitrogen, argon, and helium.

<Cooling step> The cooling step is a step of cooling the calcined body obtained in the calcination step to room temperature to obtain target monoclinic vanadium dioxide.

By performing an oxidation treatment step of switching from an inert gas environment to an oxygen-containing environment during the cooling of the calcined body obtained from the vanadium oxide compound of V ₄ O ₇ and/or V ₅ O ₉ in the calcination step, V ₄ O ₇ and/or V ₅ O ₉ vanadium oxide compounds can be converted to monoclinic vanadium dioxide. The cooling rate is not particularly limited, but is usually 200°C/hour or less, preferably 30°C/hour to 100°C/hour.

From the viewpoint of efficiently oxidizing the vanadium oxide compound of V ₄ O ₇ and/or V ₅ O ₉ , the oxygen concentration in the oxygen-containing environment is preferably 10 vol% or more, and more preferably 15% by volume to 100% by volume.

The temperature for switching from an inert gas environment to an oxygen-containing environment is preferably 35°C to 180°C, and more preferably 35°C to 150°C. The reason is that if the switching temperature is less than 35°C, it is difficult for the calcined body containing the vanadium oxide compound of V ₄ O ₇ and/or V ₅ O ₉ to be converted into monoclinic vanadium dioxide. If the switching temperature exceeds 180°C, there is a tendency to form a calcined body mainly composed of non-monoclinic VO ₂ .

After switching from an inert gas environment to an oxygen-containing environment, it is preferably maintained at 35°C to 180°C, and more preferably at 35°C to 150°C. The retention at this temperature is not particularly limited, as long as the diffraction peak of the vanadium oxide compound of V ₄ O ₇ and/or V ₅ O ₉ is not substantially observed in the X-ray diffraction analysis. The holding time is usually 10 minutes or more, preferably 10 minutes to 5 hours. In addition, the diffraction peak of the vanadium oxide compound in which V ₄ O ₇ and/or V ₅ O ₉ are not substantially observed means a range that does not affect the physical properties of the vanadium dioxide generated, and does not necessarily mean that it completely disappears. In addition, if necessary, the calcined body after the oxidation treatment is crushed, disintegrated, classified, etc., to produce a product.

The vanadium dioxide obtained by the above production method is preferably a monoclinic vanadium dioxide whose purity during X-ray diffraction analysis is high and is represented by the following general formula (1): V _1-x M _x O ₂ (1) (In the formula, M represents at least one kind or two or more kinds of sub-component elements selected from the group of Cr, W, Mo, Nb, Ta, Os, Ir, Ru, and Re. x Means 0≦x≦0.5).

In addition, regarding the physical properties of the vanadium dioxide obtained by the above manufacturing method, the average particle diameter of the primary particles obtained by the scanning electron microscope (SEM) observation method is preferably 100 nm or less, and more preferably 20 nm At ~80 nm, the specific surface area of Brunauer-Emmett-Teller (BET) is preferably 30 m ² /g or more, and more preferably 35 m ² /g to 70 m ² /g. In addition, in this specification, the average primary particle diameter determined by the SEM observation method is defined as 100 particles arbitrarily extracted from the SEM image of the vanadium dioxide sample, and the primary particle diameter of each particle is measured. Calculate the average of these values.

The vanadium dioxide obtained by the above production method can be expected to be used as a heat storage material in addition to a material that exhibits thermochromism, that is, optical properties such as transmittance or reflectance that change reversibly according to temperature. [Example]

Hereinafter, the present invention will be described in more detail with examples, but the present invention is not limited to these examples. <X-ray diffraction analysis> X-ray diffraction analysis was performed using the D8 Advance S manufactured by Bruker. Cu-Kα is used as the radiation source. The measurement conditions were set to a tube voltage of 40 kV, a tube current of 40 mA, and a scanning speed of 0.1˚/sec.

[Example 1] <Raw material mixing step> At room temperature (20°C), 400 g of V ₂ O ₅ , oxalic acid·dihydrate salt 1108 g, and ion-exchanged water 2000 g were added to a container, followed by room temperature ( Stir at 20°C for 24 hours to dissolve the raw materials in water to prepare a raw material solution. Then, to a spray drying device having a hot air inlet temperature of 220°C and an outlet temperature of 120°C, a raw material solution was supplied and spray dried to obtain a raw material mixture. The results of X-ray diffraction analysis of the obtained raw material mixture are shown in FIG. 1. As can be seen from FIG. 1, no diffraction peak of V ₂ O ₅ was observed in the raw material mixture, and it was confirmed to be amorphous. In addition, the SEM image of the obtained raw material mixture is shown in FIG. 2.

<Calcination step> The raw material mixture obtained in the raw material mixing step was put into an alumina crucible, and calcined at 350° C. for 4 hours in a nitrogen atmosphere furnace to obtain a calcined body.

<Cooling step, oxidation treatment step> After calcination, at 45°C during cooling, the furnace was switched from a nitrogen environment to an atmospheric environment (oxygen content of 21% by volume), and directly maintained at 45°C for 30 minutes for oxidation treatment. Then, the one obtained by crushing the calcined body with a bead crushing device was used as a vanadium dioxide sample.

The results of X-ray diffraction analysis of the obtained vanadium dioxide sample are shown in FIG. 3. As can be seen from FIG. 3, it was confirmed that the monoclinic vanadium dioxide with high purity at the time of X-ray diffraction analysis was obtained.

[Comparative Example 1] In Example 1, a sample was prepared in the same manner as in Example 1, except that the oxidation treatment was not performed, and after calcination, the temperature of the nitrogen atmosphere was maintained and cooled to room temperature (20°C).

The results of X-ray diffraction analysis of the obtained sample are shown in FIG. 4. As can be seen from FIG. 4, the diffraction peak of monoclinic vanadium dioxide is not observed, and the diffraction peak of V ₄ O ₇ is observed.

[Example 2 to Example 5] <Raw material mixing step> V ₂ O ₅ , oxalic acid·dihydrate salt, and ion-exchanged water were added to the container at the room temperature (20° C.) in the formulation amounts shown in Table 1, and then in the room. Stir at a temperature (20°C) for 24 hours to dissolve the raw materials in water to prepare a raw material solution. Then, to the spray-drying apparatus which set the temperature of the hot-air inlet to 220 degreeC and the outlet temperature to 120 degreeC, the raw material solution was supplied and spray-dried, and the raw material mixture was obtained. The obtained raw material mixture was subjected to X-ray diffraction analysis. As a result, no diffraction peak of V ₂ O ₅ was observed in the raw material mixture, and it was confirmed to be amorphous.

<Calcination step> The raw material mixture obtained in the raw material mixing step was put into an alumina crucible and calcined in a furnace in a nitrogen atmosphere under the conditions shown in Table 1 to obtain a calcined body.

<Cooling step, oxidation treatment step> After calcination, the conditions shown in Table 1 were switched from a nitrogen environment to an atmospheric environment (oxygen content 21% by volume) during cooling, and oxidation treatment was performed at the holding temperature and holding time shown in Table 1. Then, the one obtained by crushing the calcined body with a bead crushing device was used as a vanadium dioxide sample.

X-ray diffraction analysis was performed on the obtained vanadium dioxide sample, and as a result, it was confirmed that a monoclinic vanadium dioxide with high purity at the time of X-ray diffraction analysis was obtained. In addition, the SEM image of the vanadium dioxide sample obtained in Example 2 is shown in FIG. 5.

[Comparative Example 2] In Example 2, the sample was prepared in the same manner as in Example 2 except that it was not subjected to oxidation treatment, and after being calcined, it was cooled to room temperature (20° C.) while maintaining a nitrogen atmosphere.

The results of X-ray diffraction analysis of the obtained sample are shown in FIG. 6. As can be seen from FIG. 6, the diffraction peak of monoclinic vanadium dioxide is not observed, and the diffraction peak of V ₄ O ₇ is observed.

[Comparative Example 3] In Example 3, a sample was produced in the same manner as in Example 3 except that the calcination temperature in the calcination step was changed to 370°C.

X-ray diffraction analysis was performed on the obtained sample, and as a result, no diffraction peak of monoclinic vanadium dioxide was observed, and a diffraction peak of V ₅ O _{9 was} observed.

[Comparative Example 4] <Raw material mixing step> 20 g of V ₂ O ₅ , oxalic acid·dihydrate salt 13.86 g and ion-exchanged water 100 g were added to a container at room temperature (25°C), and then the temperature was raised to 80°C Heat treatment was carried out for 3 hours to obtain a slurry of a raw material mixture in which a part of V ₂ O ₅ was dissolved. Next, the slurry of the raw material mixture was supplied and spray-dried to a spray drying apparatus that set the temperature of the hot air inlet to 220°C and the outlet temperature to 120°C to obtain a reaction precursor. X-ray diffraction analysis was performed on the obtained reaction precursor, and as a result, a diffraction peak of V ₂ O ₅ was confirmed.

<Calcination step and cooling step> The reaction precursor obtained in the raw material mixing step was put into an alumina crucible and calcined at 330°C for 4 hours in a furnace in a nitrogen atmosphere. After calcination, directly cool to room temperature (20°C) under nitrogen environment. Then, a sample obtained by crushing the calcined body with a bead crushing device was used as a sample.

X-ray diffraction analysis was performed on the obtained sample, and as a result, a mixture of V ₂ O ₅ and monoclinic vanadium dioxide was confirmed.

[Comparative Example 5] In Comparative Example 4, after calcination, the furnace was switched from a nitrogen environment to an atmospheric environment (oxygen content of 21% by volume) at 50°C during cooling, and it was directly maintained at 50°C for 30 minutes to perform oxidation treatment. In the same manner as in Comparative Example 4, a sample was prepared.

X-ray diffraction analysis was performed on the obtained sample, and as a result, a mixture of V ₂ O ₅ and monoclinic vanadium dioxide was confirmed.

[Comparative Example 6] In Example 2, the sample was produced in the same manner as in Example 2 except that the calcination temperature in the calcination step was changed to 330°C.

The results of X-ray diffraction analysis of the obtained sample are shown in FIG. 7. As can be seen from FIG. 7, a mixture of V ₃ O ₇ and monoclinic vanadium dioxide was confirmed.

[Table 1]

[Example 6] <Raw material mixing step> 300 g of V ₂ O ₅ , 581.3 g of oxalic acid·dihydrate salt, 1500 g of ion-exchanged water, and 5 g of ammonium metatungstate solution (50% by weight in WO ₃ ) 5 g It was added to the container at room temperature (20°C), and then stirred at room temperature (20°C) for 24 hours to dissolve the raw materials in water to prepare a raw material solution. Furthermore, the molar ratio (C/V) of the carbon atoms in oxalic acid·dihydrate to the vanadium atoms in V ₂ O ₅ was 2.8. Then, to the spray-drying apparatus which set the temperature of the hot-air inlet to 220 degreeC and the outlet temperature to 120 degreeC, the raw material solution was supplied and spray-dried, and the raw material mixture was obtained. X-ray diffraction analysis was performed on the obtained raw material mixture. As a result, no diffraction peak was observed and it was confirmed to be amorphous.

<Calcination step> The raw material mixture obtained in the raw material mixing step was put into an alumina crucible and calcined at 360°C for 4 hours in a furnace in a nitrogen atmosphere to obtain a calcined body.

<Cooling step, oxidation treatment step> After calcination, the furnace was switched from a nitrogen environment to an atmospheric environment (oxygen content 21% by volume) at 60°C during the cooling process, and directly maintained at 60°C for 30 minutes for oxidation treatment. Then, the calcined body was crushed by a bead crushing device and obtained as a vanadium dioxide sample doped with 0.7% by mass of W atoms.

X-ray diffraction analysis was performed on the obtained vanadium dioxide sample, and as a result, it was confirmed that a monoclinic vanadium dioxide with high purity at the time of X-ray diffraction analysis was obtained.

[Physical Properties Evaluation] For each sample obtained in Examples and Comparative Examples, the average primary particle diameter and BET specific surface area were measured. The results are shown in Table 2. In addition, the results of X-ray diffraction analysis of each sample are also shown in Table 2.

[Table 2]

In addition, this international application claims priority based on Japanese Patent Application No. 2018-143546 filed on July 31, 2018, and the entire contents of this Japanese patent application are cited in this international application.

no

1 is an X-ray diffraction diagram of a raw material mixture obtained by the raw material mixing step of Example 1. FIG. 2 is a scanning electron microscope (SEM) image of the raw material mixture obtained by the raw material mixing step of Example 1. FIG. 3 is an X-ray diffraction diagram of a vanadium dioxide sample obtained in Example 1. FIG. 4 is an X-ray diffraction chart of the sample obtained in Comparative Example 1. FIG. 5 is an SEM image of a vanadium dioxide sample obtained in Example 2. 6 is an X-ray diffraction chart of the sample obtained in Comparative Example 2. FIG. 7 is an X-ray diffraction chart of the sample obtained in Comparative Example 6. FIG.

Claims (9)

A manufacturing method of vanadium dioxide, which is characterized by including: In the raw material mixing step, vanadium pentoxide is mixed with the carbon material source to obtain a raw material mixture; A calcination step, calcining the raw material mixture in an inert gas environment at a temperature above 340°C and less than 370°C to obtain a calcined body; and In the cooling step, the calcined body is cooled to room temperature, In the raw material mixing step, the molar ratio (C/V) of the carbon atoms in the carbon material source to the vanadium atoms in the vanadium pentoxide is 2.2 or more, The cooling step includes an oxidation treatment step, switching from an inert gas environment to an oxygen-containing environment during cooling. The method for producing vanadium dioxide as described in item 1 of the patent application range, wherein the temperature from the inert gas environment to the oxygen-containing environment is 35°C to 180°C, and after switching, the temperature is 35°C to 180°C Keep at temperature for 10 minutes to 5 hours. The method for manufacturing vanadium dioxide as described in item 1 or item 2 of the patent application scope, wherein in the raw material mixing step, the carbon material source is an organic acid, and the raw material mixing step includes: The two vanadium and the organic acid are mixed in an aqueous solvent to obtain a raw material solution in which each raw material is dissolved, and then the spray drying process is performed on the raw material solution. The method for producing vanadium dioxide as described in item 3 of the patent application range, wherein in the raw material mixing step, the molar ratio of carbon atoms in the organic acid relative to vanadium atoms in the vanadium pentoxide (C/V) is 2.2 to 4.5. The method for producing vanadium dioxide as described in item 3 or item 4 of the patent application, wherein the organic acid is a carboxylic acid. The method for producing vanadium dioxide according to any one of claims 3 to 5, wherein the organic acid is oxalic acid. The method for producing vanadium dioxide according to any one of the first to sixth patent application scopes, wherein the raw material mixing step further includes a step of adding a subsidiary component element. The method for manufacturing vanadium dioxide as described in Item 7 of the patent application range, wherein the auxiliary component element is one or two selected from Cr, W, Mo, Nb, Ta, Os, Ir, Ru, and Re the above. The method for manufacturing vanadium dioxide according to any one of the first to eighth items of the patent application range, wherein the average primary particle size of the manufactured vanadium dioxide is 100 nm or less.

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