WO2005111272A1

WO2005111272A1 - Process for producing microparticles by plasma-induced electrolysis

Info

Publication number: WO2005111272A1
Application number: PCT/JP2005/006792
Authority: WO
Inventors: Yasuhiko Ito; Takuya Goto; Hiroyuki Kawamura
Original assignee: Iox Co., Ltd.; The Doshisha
Priority date: 2004-04-06
Filing date: 2005-04-06
Publication date: 2005-11-24
Also published as: JPWO2005111272A1; JP4688796B2

Abstract

There are provided: a process for producing metal microparticles, characterized in that an oxide of metal species (metal belonging to Group 3, Group 4, Group 5, Group 6, Group 7, Group 8, Group 9, Group 10, Group 11, Group 12, Group 13 or Group 14) of metal microparticles is melted in an electrolytic bath and that a molten salt electrolysis is carried out with a negative electrode disposed in the vicinity of the electrolytic bath; a process for producing metal microparticles, characterized in that a molten salt electrolysis is carried out with a positive electrode containing the metal species disposed in a molten salt and with a negative electrode disposed in the vicinity of an electrolytic bath, or a method of recycling used metal by the use of these production processes; a method of recycling a metal, characterized in that a molten salt electrolysis is carried out with used metal melted into an electrolytic bath and with a negative electrode disposed in the vicinity of the electrolytic bath to thereby obtain metal microparticles; and a method of recycling a metal, characterized in that a molten salt electrolysis is carried out with used metal utilized as a positive electrode material and with a negative electrode disposed in the vicinity of an electrolytic bath to thereby obtain metal microparticles.

Description

Method for producing fine particles by plasma-induced electrolysis

Technical field

The present invention relates to a method for producing metal fine particles by molten salt electrolysis and a recycling method.

[0002] Metal fine particles are widely used in the field of industrial materials such as magnetic recording media, photocatalysts, pigments, battery electrodes, and catalysts because they have higher functionality than bulk materials and have better processability of products. I have.

[0003] As a conventional method for producing metal fine particles, a method using plasma induced by arc discharge or the like in a gas has recently attracted attention (for example, Patent Documents 1 and 2). In this technique, a voltage is applied between a discharge electrode arranged in close proximity and a base material as a raw material to generate plasma, and the base material is evaporated and solidified to form fine particles. Alternatively, a voltage is applied between a plurality of discharge electrodes arranged close to each other to generate plasma, a raw material is supplied in the plasma, and the raw material is evaporated and solidified to form fine particles.

[0004] However, in the conventional manufacturing method using plasma induced by arc discharge in a gas, it is necessary to maintain a discharge starting voltage of several kV and a gas atmosphere of several atmospheres. Since the plasma current value reaches 100-200A, it requires expensive equipment and facilities, and advanced technology associated with it. In addition, there is a risk that the equipment may be deteriorated or destroyed due to high temperatures, and it is not always technically and economically efficient. Furthermore, this technique generally requires a high-purity raw material, and scrap or the like is not used as a raw material.

[0005] Therefore, there is a demand for a method for easily generating metal fine particles under safe conditions or an inexpensive device. In addition, if metal particles can be obtained from scrap-like or massive metal compounds that can be used only with pure metal compounds, and (oxidized) metal compounds that have been used for various industrial purposes, metal can be reused. Possible and highly desirable in terms of the global environment Patent Document 1: JP 2002-241811

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-045684

Disclosure of the invention

Problems to be solved by the invention

[0006] A main object of the present invention is to provide a method for producing fine metal fine particles and a method for recycling.

Means for solving the problem

[0007] As a result of diligent studies, the present inventors have found that the above object can be achieved by incorporating a raw material of metal fine particles in a molten salt or an anode and performing molten salt electrolysis, and have achieved the present invention. It was completed.

[0008] That is, the present invention relates to a method for producing the following metal fine particles.

Item 1.

At least one metal selected from the group consisting of metals belonging to Group 3, 4, 5, 6, 7, 8, 9, 9, 10, 11, 12, 13, and 14 A method for producing fine metal particles, comprising: melting a metal raw material containing an oxide of the above in an electrolytic bath; and performing a molten salt electrolysis by placing a cathode near the electrolytic bath.

Section 2.

The metal raw material includes an oxide of at least one metal selected from the group consisting of titanium, zirconium, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, platinum, cobalt, nickel and silicon. The method according to item 1 to be performed.

Section 3.

Group consisting of metals belonging to groups 3, 4, 5, 6, 7, 8, 9, 9, 10, 11, 12, 13, and 14 at least one metal selected from the group consisting of Wherein the anode containing at least one selected from the group consisting of the metal and a compound of the metal is placed in a molten salt, and the cathode is placed near the electrolytic bath to form the molten salt. A method for producing metal fine particles, comprising performing electrolysis.

Section 4.

The molten salt is selected from the group consisting of a metal and a metal compound as a raw material of the metal fine particles. Item 4. The method according to Item 3, containing at least one of the following.

Section 5.

Item 5. The method according to any one of Items 1 to 4, wherein the molten salt electrolysis is performed by setting an electric resistance between the power supply and the anode.

Section 6.

A metal recycling method characterized by melting used metal in an electrolytic bath, installing a cathode near the electrolytic bath and performing molten salt electrolysis to obtain fine metal particles.

Section 7.

A metal recycling method comprising using used metal as an anode material, and installing a cathode near an electrolytic bath and performing molten salt electrolysis to obtain fine metal particles. According to the present invention, a metal raw material (a material serving as a raw material of metal fine particles) in a molten salt is produced as metal fine particles by installing a cathode in the vicinity of the electrolytic bath without in contact with the electrolytic bath and inducing plasma. On how to do it. That is, a metal power belonging to 3, 4, 5, 6, 7, 8, 9, 9, 10, 11, 12, 13, and 14 groups. A method for producing fine metal particles, comprising dissolving a metal raw material containing a metal oxide in an electrolytic bath, and performing electrolysis by inducing a plasma by setting a cathode near the electrolytic bath (hereinafter, referred to as a method of producing fine metal particles). Manufacturing method 1). In this method, metal particles are produced by performing a plasma discharge on a metal raw material in a molten salt.

Further, the present invention provides (1) a group consisting of metals belonging to groups 3, 4, 5, 6, 7, 7, 8, 9, 10, 11, 12, 13, and 14. An anode containing at least one selected from the group consisting of at least one metal selected from the group consisting of: (2) a compound of the metal; and an anode containing at least one selected from the group consisting of: The present invention relates to a method for producing metal particles, which is characterized by performing salt electrolysis (hereinafter, may be referred to as production method 2). In this method, the metal or metal compound contained in the anode is ionized and eluted into the molten salt by the molten salt electrolysis. Then, a metal and Z or a metal compound (not limited to metal oxide) serving as a raw material of the fine particles are added to the molten salt. However, the raw material is supplied from the anode, and the metal fine particles can be continuously produced. Alternatively, a metal and a metal compound as raw materials of fine particles are contained in a molten salt. In addition, in some cases, the metal or metal compound which also eluted the anodic force is subjected to plasma discharge near the cathode to produce metal fine particles.

[0010] In these production methods, when metal oxides (for example, used metal oxides) are used as raw materials to obtain fine metal particles, they are extremely excellent in terms of economy and recycling.

[0011] The method of the present invention will be described below. In the present invention, an apparatus for performing molten salt electrolysis is

An apparatus generally used for performing molten salt electrolysis can be used.

[0012] Electrolytic bath

In the present invention, an electrolytic bath generally used in molten salt electrolysis can be used as the electrolytic bath. For example, alkali metal halide, alkaline earth metal halide, alkali metal carbonate, alkaline earth metal carbonate, alkali metal sulfate, alkaline earth metal sulfate, alkali metal nitrate, alkaline earth metal It is preferable to use a molten salt obtained alone or in combination of two or more of nitrates as a solvent for the electrolytic bath.

[0013] Examples of the alkali metal halide include LiF, NaF, KF, RbF, CsF, LiCl, NaCl, KC1, RbCl, CsCl, LiBr, NaBr, KBr, RbBr, CsBr, Lil, Nal, KI, Rbl, Csl. And the like. Examples of the alkaline earth metal halide include MgF, CaF, SrF, BaF, MgCl, CaCl,

2 2 2 2 2 2

SrCl, BaCl, MgBr, CaBr, SrBr, BaBr, Mgl, Cal, Sri, Bal etc. S can be used.

2 2 2 2 2 2 2 2 2 2

[0014] The above compounds can be used alone or in combination of two or more. The combination of these compounds, the number of compounds to be combined, the mixing ratio, and the like are not limited, and can be appropriately selected according to the type of metal to be electrolyzed. In the present invention, KCl and / or LiCl melted (LiCl: KCl = about 35 mol% to 100 mol%: about 65 mol% to 0 mol%, preferably about 55 mol% to 65 mol%: about 45 mol% to 35 mol% ), Molten NaCl and KC1 (NaCl: KCl = about 30 mol% to 70 mol%: about 70 mol% to 30 mol%, preferably about 45 mol% to 55 mol%: about 55 mol% to 45 mol%), LiCl, KC1 and It is preferable to use a material in which CsCl is melted (a eutectic composition of LiCl: KCl: CsCl = 57.5: 13.3: 29.2 mol% is preferable, but a composition ratio of each of which is changed by about 20% is also preferable).

[0015] In such a solvent, a metal compound (hereinafter, referred to as "metal raw material" or By dissolving an “ion source” and performing molten salt electrolysis, metal fine particles can be obtained. When the anode contains a metal or a metal compound as a raw material of the metal fine particles, the addition of the metal raw material to the molten salt is optional.

Further, the electrolytic bath in the present invention may contain other impurities, a solubilizing agent, an electrolytic assisting agent, and the like as long as the properties of the obtained metal fine particles are not impaired.

[0017] Metal raw material (ion source)

The metal fine particles obtained by the method of the present invention are selected from metals belonging to groups 3, 4, 5, 6, 6, 7, 8, 9, 10, 11, 12, 13, and 14. At least one kind of metal fine particles selected from the group consisting of: Among the above metals, titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), chromium (Cr), platinum (Pt ), Cobalt (Co), nickel (Ni), and silicon (Si).

Therefore, in the production method 1, at least one of the above-mentioned metal oxides is contained in the electrolytic bath as a metal raw material as a raw material of these metal fine particles. The metal raw material may be a mixture of a metal oxide or a metal or a metal compound, or a metal or metal compound. Further, other components may be included.

[0019] Titanium oxides include TiO, TiO, and TiO; zirconium oxides include ZrO

2 2 3

Etc .; Vanadium oxides include VO, VO, V 0, V 0, V 0 etc .; Niobium oxide

2 2 2 3 2 4 3 5

NbO, NbO, Nb 0, etc .; tantalum oxide as TaO, TaO, etc .; molybdenum

2 2 5 2 5

Oxides such as MoO and MoO; tungsten oxides such as WO and WO;

The oxides of 232 rom include CrO, CrO, Cr 0 and the like; the oxides of platinum include PtO, PtO,

2 2 3 3 4

PtO, etc .; oxides of cobalt, CoO, Co O, etc .; oxides of nickel, NiO

2 3 4

, Ni O (0.003 <x <0.17); Examples of silicon oxide include SiO and SiO 2.

l-x 2

[0020] The metal oxide may be a naturally oxidized metal or a used metal used for various purposes. Examples of the used metal include metals used in magnetic recording media, photocatalysts, pigments, fuel cells, catalysts, and the like. By performing molten salt electrolysis using such a metal oxide, it is possible to recycle used metal. When one kind of metal is used as the metal raw material, fine metal particles composed of a single metal atom can be obtained. When two or more kinds of metal are used as the metal raw material, alloy fine particles can be obtained. Fine metal particles (comprising a plurality of metals) can also be obtained. Therefore, metal fine particles include alloy fine particles.

As the metal compound, sulfates, nitrates, phosphates, halides (such as chlorides, fluorides, bromides, and iodides) of the above metals can be used. For example, K TaF, NiCl, K TiF

2 7 2 2 6

, AgCl, K TaF, VC1, K NbF, K MoO, K WO, CrCl, K PtCl, CoCl, K SiF force ^

2 6 2 2 7 2 4 2 4 2 2 6 2 2 6 The metal compounds can be used alone or in combination of two or more.

In the method of the present invention, the shape of the metal raw material used is not limited. For example, various shapes such as a scrap shape, a lump shape, or a powder shape may be used. Moreover, after using for various purposes, it is also possible to take out the metal part and use it as it is.

[0024] The amount of the metal compound and the oxide of Z or metal added to the electrolytic bath is not limited, and can be appropriately selected according to the electrolysis time, the amount and size of the fine particles. For example, the metal raw material should be dissolved in an amount of about 0.0001 to 10 mol / L, preferably about 0.1 to 5.0 mol / L per solvent of the electrolytic bath.

[0025] In the production method 2 of the present invention, since the metal raw material is supplied with an anodic force by electrolysis, the addition of the metal raw material to the electrolytic bath can be arbitrarily selected. When a metal raw material is added to the electrolytic bath, the metal raw material may be any one selected from the group consisting of a metal and a metal compound which are raw materials for fine particles. Therefore, in Production Method 1, a metal oxidant is indispensable as a metal raw material, but in Production Method 2, the metal raw material added to the molten salt is not limited to a metal oxidant, but may be a metal or metal. The compounds can be used widely. Further, in the production method 2, since the metal raw material is supplied from the anode, the concentration of the metal raw material to be added to the molten salt can be reduced as compared with the case of the production method 1. . In the case where the type of metal of the metal source supplied from the anode is different from the type of metal of the metal source added to the molten salt, fine particles of an alloy are obtained. Included in particles.

[0026] (1) Anode

In the production method 1 of the present invention, as the anode, an electrode generally used as an anode in molten salt electrolysis can be used, and is not particularly limited. For example, carbon materials such as glass, graphite, conductive diamond and the like, tantalum, tungsten, molybdenum, platinum and the like can be used as electrodes. Also, a thin film formed of a metal such as tantalum, tungsten, molybdenum, or platinum on a dissimilar material can be used as the anode. In addition, used metals can be used as anode materials. In addition, when it is required to suppress the generation of chlorine gas, it can be suppressed by allowing the anode to contain a fine particle source metal or a compound of the metal.

[0027] In the production method 2 of the present invention, the anode may be (1) a group of 3, 4, 5, 6, 7, 8, 8, 9, 11, 12, 13, At least one metal selected from the group consisting of metals belonging to Group 14 and Group 14; and (2) a compound of the metal; Preferred metal species are the same as the preferred metal species of the metal fine particles. The compound of the metal is the same as the metal compound in the metal raw material. In the present production method, generation of chlorine gas is suppressed because the anode contains a raw material of fine particles. When two or more metal species are used for the anode, since the base metal is fine particles, the combination of metal species contained in the anode is appropriately selected according to the metal species of the target fine particles.

[0028] The shape, size, and the like of the electrode used in the present invention are not limited. As the shape of the electrode, for example, a plate shape, a rod shape, a lump shape, a spring shape, a prism shape, or the like can be used.

In the present invention, when performing electrolysis, the anode is preferably immersed in an electrolytic bath so as to generally perform the electrolysis. The mode in which the entire anode is immersed or a part thereof is immersed is not particularly limited.

(0030) Cathode

As the cathode, an anode generally used for molten salt electrolysis and capable of generating plasma can be used, and is not particularly limited. For example, various metals such as iron, nickel, molybdenum, tantalum, and tungsten, alloys thereof, carbon materials such as glassy carbon and conductive diamond, conductive ceramics, and semiconductor ceramics can be used. In addition, those formed as thin films on different materials can also be used as cathodes. The Among them, it is preferable to use a high melting point metal such as tungsten or tantalum which is not easily consumed when plasma is induced.

[0031] In the present invention, it is installed near the electrolytic bath so that it is not in contact with or immersed in the electrolytic bath. The installation place is not particularly limited as long as the metal fine particles are generated in the molten salt by the plasma generated by the cathode, but it is preferable that the installation place is above the liquid level of the molten salt. By doing so, cathodic plasma is induced, and fine metal particles are generated in the electrolytic bath. The distance from the surface of the electrolytic bath to the lowermost part of the cathode is not limited, as long as the plasma is stably induced.

[0032] Plasma-induced discharge electrolysis

The electrolysis conditions in the present invention can be generally performed under the conditions for performing molten salt electrolysis, and can be appropriately selected according to the composition of the solvent, the type of target metal fine particles, and the like. For example, the voltage to be applied is preferably about 200 to 400 V in order to reduce the load on the electric circuit, for example, about 200 to 800 V. However, the voltage can be reduced to 10 to 200 V, preferably 30 to 150 V, at a stage where the generation of plasma-induced discharge is stable. The type of generated current is preferably a direct current, and the current per discharge electrode is preferably about 0.05 to 50 A, and more preferably about 0.1 to 20 A.

[0033] In the present invention, in order to stably induce plasma, it is preferable to secure electric discharge stability by inserting an electric resistor between the power supply and the electrode. The electrical resistance can be inserted on the cathode side, the anode side or both. The type of the electric resistance is not limited as long as it is a resistor having a capacity to withstand the current during electrolysis.For example, a cement resistor, an enamel resistor, a non-combustible fixed wire resistor, or the like can be used. Fixed resistors are more preferred. The value of the resistance is usually about 1 Ω to 51ίΩ, preferably 3 Ω to 31ίΩ.

[0034] The temperature of the electrolytic bath is also not limited, and can be appropriately selected according to the melting point of the solvent, the melting point of the ion source, and the like. For example, it is about 250 to 700 ° C, preferably about 400 to 500 ° C.

[0035] The electrolysis is generally performed under atmospheric pressure, but may be performed under increased or reduced pressure. In addition, examples of the inert gas which is preferably performed in an inert gas atmosphere include nitrogen, argon, and neon, and argon is preferable.

[0036] The electrolysis time is also not limited, and is appropriately selected according to the type, particle size, and the like of the target metal particles. Can. For example, it is about 0.1 to 10 hours, preferably about 1 to 5 hours.

In the present invention, by adjusting the concentration of the ion source to be added, the electrolysis time, and the like, metal fine particles having an arbitrary particle size of about 100 μm or less, preferably in the range of about lnm to 100 μm are obtained. be able to. In particular, in the present invention, very small metal particles of nano size can be obtained. For example, the size of the metal fine particles can be reduced by shortening the electrolysis time or the time until the recovery of the electrolytic power, reducing the concentration of the ion source in the electrolytic bath, or keeping the temperature of the electrolytic bath low during the electrolysis. Can be smaller.

The following mechanism is considered as a mechanism for obtaining metal fine particles by the method of the present invention. The present invention is not limited to this mechanism. When plasma-induced electrolysis is performed using the discharge electrode as a cathode, a cation M ^{n + serving as} a raw material of fine particles in a solvent is generated according to the following equation (1), and a reduction reaction of an alkali metal ion L + present in the solvent (formula (1)) According to (2)), it is reduced to an atomic substance as represented by equation (3).

[0039] M → M ^{n +} + ne "(1)

L + + e— → L (2)

^{^{nL + M n + → nL +}} + M (3)

Subsequently, atomic-level clusters are formed by collisions between atomic substances in a solvent, and furthermore, collisions between atomic-level clusters are sequentially repeated, so that fine particles of several nm or several / zm are thought to grow. .

[0040] When the cation ^{Mn + serving} as the raw material of the fine particles is supplied by anodic dissolution of the oxidized product held at the electrode portion in the solvent or by chemical dissolution of the oxidized product held in the solvent, According to the following formula (4) or (5), a cation M ^{n +} is generated in a solvent.

[0041] M → M ^{n +} + ne "(4)

MA → xM ^{y +} + yA ^x "(5)

x y

(However, M represents a metal contained in an oxide or the like, and MA represents an oxide or the like.)

There are two types of cations ( ^{Mnl +} and ^{Mn2 +} ) that serve as raw materials for fine particles in the solvent.

1 2

By simultaneously reducing the respective ions, it is also possible to form a compound (alloy) according to the following formula (6). The same applies when there are three or more ion species.

[0042] M ^{nl +} + M ^{n2 +} + (n + n) e "→ MM (6) Recovery of extra fine particles

The obtained metal particles can be recovered in the following manner. The present invention is not limited to these.

For example, electrolytic bath power A molten salt containing metal particles can be taken out, cooled and solidified, preferably in an inert gas atmosphere. The type of the inert gas is as described above. By performing the treatment in an inert gas atmosphere, oxidation of the metal fine particles can be prevented.

Next, the solidified electrolytic solution may be crushed and immersed in the cleaning solution!ヽ. The means for pulverization is not limited, and may be, for example, a hammer, a mixer, or the like. The device for performing the ultrasonic treatment is not limited, and a commercially available device can be used. The condition of the ultrasonic wave is not limited.For example, the ultrasonic treatment may be performed at a frequency of about 10 to 100 kHz, about 20 to 60 kHz, for about 100 to 300 minutes per 100 g of the solidified electrolyte, preferably about 150 to 200 minutes.ヽ.

After the ultrasonic treatment, the metal particles of the present invention can be obtained by washing and centrifuging. The condition of the centrifugation is not limited as long as the metal fine particles obtained in the present invention and the solidified electrolyte are separated, and can be appropriately selected. For example, the speed can be about 1000 to 5000 rpm, preferably about 1500 to 3000 rpm, and about 10 minutes to 2 hours, preferably about 30 minutes to 1.5 hours.

The washing method is not limited as long as the metal fine particles obtained in the present invention can be subjected to ultrasonic wave, centrifugal separation, and the like. For example, water, an aqueous solution in which a reducing agent generally used for electroless plating is dissolved, or the like can be used. As the reducing agent, borane-amine complexes such as dimethylamine borane and trimethylamine borane; borohydride compounds such as potassium borohydride and sodium borohydride; formaldehyde and the like can be used. These concentrations are not limited.

[0047] If necessary, ultrasonic treatment and centrifugation of the precipitate may be repeated. By repeating the process, metal fine particles can be obtained with high efficiency from the solidified electrolytic solution.

[0048] The particle size of the obtained metal particles can be determined by a conventional method such as observation with an electron microscope. The particle size distribution can also be determined by a conventional method such as dynamic light scattering measurement. More Furthermore, the oxygen content in the metal fine particles can also be determined by a conventional method such as, for example, an electroinert gas melting infrared absorption method.

[0049] It is also possible to use those obtained by further adding a dispersant or the like containing a nonionic surfactant, alcohol or the like to the cleaning solution to the obtained metal fine particles. The metal fine particles may be washed with an appropriate liquid when used, and used for a desired purpose.

[0050] Recycling method

The recycling method of the present invention utilizes the above-described method for producing fine metal particles, and uses a used metal or metal compound as a metal raw material. That is, the used metal or metal compound is added to the molten salt as a metal raw material, or is held at the anode. As a result, fine metal particles corresponding to the metal species of the used metal or metal compound are generated, so that the used metal or metal compound can be reused.

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to FIG.

For example, a holder (3) for installing a high-purity aluminum crucible (2) as an electrolytic cell in an electric furnace (1) capable of heating at about 500 ° C is provided. The inert gas is circulated at atmospheric pressure through the inlet pipe (4) and the exhaust pipe (5). In a crucible, the alkali metal halide is melted and used as a solvent (6) for the electrolytic bath. The temperature of the solvent is measured with a thermocouple (7) and set to a predetermined temperature.

[0052] In a state where the inert gas is circulated, an ion source serving as a raw material of the metal fine particles is added to the solvent. Next, a power supply device (10) is installed between the discharge electrode (8) placed on the solvent and the electrode (9) placed in the solvent, and a voltage is applied to connect the solvent and the discharge electrode. Plasma is induced in between.

[0053] Instead of adding the ion source, the electrode (9) in the solvent may have a portion capable of holding the substance (11) containing the raw material of the metal fine particles. By doing so, it is possible to stably or continuously supply an ion source serving as a raw material of metal fine particles during electrolysis. The ion source may be held in a solvent other than the electrode.

When plasma is induced, by inserting an electric resistance (12) or the like between the power supply device and the electrode, the plasma can be induced stably, and the electrolysis is promoted, so that the metal fine particles can be efficiently produced. It is preferable because it is formed. The invention's effect

[0055] The method for producing metal fine particles of the present invention is particularly excellent in that not only the metal but also an oxide of the metal can be used as a raw material of the metal fine particles. Further, by controlling parameters such as electrolyte composition, electrolyte temperature, and electrolysis time in molten salt electrolysis, the particle size, particle size distribution, and the like of the fine particles can be easily controlled.

[0056] The present invention does not require expensive equipment and equipment, and does not require advanced knowledge or advanced technology, and can produce desired fine metal particles. Therefore, the production cost of metal particles is greatly reduced. You. Also, the electrolytic bath does not contain harmful substances and can be reused.

Further, as the form of the metal raw material used as the raw material of the metal fine particles, it is possible to produce the metal fine particles by using a scrap or lump-shaped raw material. For example, an ion source is supplied by anodic dissolution or chemical dissolution of the substance by holding the substance containing the raw material of the microparticles to be produced in the electrode part disposed in the solvent in the electrolytic bath or in the solvent. it can. In other words, since the state force such as scrap can again produce a material necessary for the device, the method of the present invention is very excellent as a metal recycling method.

Brief Description of Drawings

FIG. 1 is a conceptual diagram of an apparatus for performing molten salt electrolysis.

FIG. 2 (a) shows a scanning electron micrograph of the tantalum fine particles obtained in Example 1, and FIG. 2 (b) shows the analysis result of the white rectangular portion of (a) by an X-ray microanalyzer.

[FIG. 3] (a) shows a scanning electron micrograph of the tantalum fine particles obtained in Example 3, and (b) shows the result of X-ray diffraction of the tantalum fine particles.

Explanation of symbols

[0059] 1 Electric furnace

2 Crucible

3 Holder

4 Introduction pipe

5 Exhaust pipe

6 Solvent

7 Thermocouple 8 electrodes

9 electrodes

10 Power supply

11 Raw material holding section

12 Electric resistance

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, examples will be shown to further clarify the features of the present invention. The present invention is not limited to these examples.

Example

Example 1

LiCl—KCl (58.5: 41.5mol%; 100g in total) mixed in a eutectic composition was vacuum-dried at 180 ° C for several days in the solvent (electrolytic bath) and then melted at 450 ° C in an argon atmosphere. I used something. Heptafluorotantalum potassium (K TaF) was used as the tantalum source.

2 7

So help! ]did.

[0062] A tungsten wire was placed on a solvent as a discharge electrode (cathode), and tantalum condenser scrap (pin scrap) was placed in the solvent as an anode.

twenty five

However, a cylindrical tantalum metal electrode holding the garnish was 0.5% by weight of the entire scrap was disposed. Under an argon atmosphere, maintain the solvent temperature at 450 ° C, apply 250 V between the discharge electrode and the electrode in the solvent, induce a plus and minus between the discharge electrode and the solvent, and Electrolysis was performed.

[0063] After the plasma-induced electrolysis, the solvent containing the fine particles is cooled and solidified to room temperature under an argon atmosphere, subjected to ultrasonic treatment for several hours in a 2M aqueous hydrazine solution until the solidified solvent is dissolved, and then left for about 10 minutes. The sonication and the centrifugation operation were repeated. The centrifugation operation was performed at 2000 rpm, and the first time was about 10 minutes, the second time was about 30 minutes, and the third time was about 60 minutes.

As a result, black tantalum fine particles were collected. Observation of the fine particles with a scanning electron microscope confirmed that fine particles on the order of nanometers were obtained, as shown in 02 (a). Subsequently, an X-ray microanalyzer measurement was performed on the obtained fine particles (white rectangular portion in FIG. 2 (a)), and it was confirmed that tantalum fine particles were formed (FIG. 2). (b) ) o

[0065] Further, since the mass of the pin dust in the cylindrical tantalum metal electrode arranged in the solvent is reduced to 0.996 g after the electrolysis, the tantalum metal or the tantalum metal contained in the pin scrap is reduced. Was dissolved during electrolysis. On the other hand, the consumption of the cylindrical tantalum metal electrode was 0.325 g.

[0066] The K TaF force equivalent to 0.1 mol% added in a solvent is also the theoretical value of fine particles obtained by electrolysis.

2 7

The mass is 0.32 g, and the fine particles collected for force analysis alone exceed 0.4 g, and it can be said that tantalum fine particles were formed from pin scraps or a tantalum ion source obtained by melting from a tantalum metal electrode. It was confirmed that the present invention can be used as a resource recycling type process using scrap as a raw material.

[0067] Detail 12

Metal compounds other than tantalum include nickel (using NiCl as an ion source), titanium (using

2

K TiF as an ion source), silver (AgCl as an ion source), zirconium (ion

2 6

K ZrF as source), vanadium (using VC1 as ion source), niobium (with ion source)

2 6 2

Using KNbF), molybdenum (using KMoO as ion source), and tungsten (using

2 7 2 4

K WO), chromium (using CrCl as ion source), platinum (as ion source)

2 4 2

K PtCl) and cobalt (CoCl is used as ion source).

2 6 2

An experiment was conducted in the same manner as in Example 1 except that scrap (pin scrap) of the above-mentioned metal compound was used in place of the scrap (pin scrap) of the metal capacitor. As a result, metal particles of the same nanoorder were obtained. Was done.

Example 3

Under conditions that do not contain heptafluorotantalum potassium as the ion source, a cylindrical graphite electrode holding 1.502 g of tantalum condenser scrap (pin scraps) in a solvent was placed as the anode, and the current value was set to 0.80 A. The experiment was performed in the same manner as in Example 1 except that the electrolysis was performed for 1.7 hours. X-ray diffraction of the obtained fine particles confirmed that they were tantalum fine particles with a lattice constant of about 3% wider.

[0069] The mass of pin debris in the cylindrical graphite electrode placed in the solvent was reduced to 0.903 g after electrolysis, and the power of only the tantalum ion source obtained by dissolving the pin debris also reduced the tantalum fineness. It was confirmed that particles were formed. In this embodiment, tantalum fine particles are formed in the solvent without containing an ion source in advance and only the scrap is held, and the present invention is a resource circulation type process using only scrap as a raw material. It was confirmed that it was more effective.

Example 4

NiCl (nickel ion source), K TiF (titanium ion source), AgCl (silver)

2 2 6

Ion source), K ZrF (zirconium ion source), VC1 (vanadium ion source), K

2 6 2 2

NbF (niobium ion source), K MoO (molybdenum ion source), K WO (tungsten

7 2 4 2 4

Ion source), CrCl (chromium ion source), K PtCl (platinum ion source), CoCl (cobalt ion source)

2 2 6 2

When an experiment was performed in the same manner as in Example 2 without using each of the (on sources), metal fine particles of each nano-order were obtained.

In the present embodiment, the metal fine particles are formed only by the electrode that holds the scrap without previously including the ion source in the solvent, and the present invention is further described as a resource recycling process using scrap as a raw material. Confirmed to be valid.

Industrial applicability

The present invention is useful in the field of producing fine metal particles and the field of recycling metal.

Claims

The scope of the claims

[1] At least one selected from the group consisting of metals belonging to groups 3, 4, 5, 6, 7, 8, 9, 9, 10, 11, 12, 13, and 14 A method for producing fine metal particles, comprising melting a metal raw material containing an oxide of a metal in an electrolytic bath, and placing a cathode near the electrolytic bath to perform molten salt electrolysis.

[2] The metal raw material includes at least one oxide of a metal selected from the group consisting of titanium, zirconium, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, platinum, cobalt, nickel and silicon. The method according to claim 1, wherein:

[3] A group consisting of metals belonging to groups 3, 4, 5, 6, 7, 8, 8, 9, 10, 11, 12, 13 and 14 At least one selected from metals Kind Code: A1 A method for producing metal fine particles of a metal, wherein an anode containing at least one selected from the group consisting of the metal and a compound of the metal is provided in a molten salt, and the cathode is provided near an electrolytic bath. A method for producing metal fine particles, characterized in that molten salt electrolysis is carried out.

4. The method according to claim 3, wherein the molten salt contains at least one selected from the group consisting of a metal and a metal compound serving as a raw material of the metal fine particles.

[5] The method according to any one of [1] to [4], wherein molten salt electrolysis is performed by setting an electric resistance between the power supply and the anode.

[6] A method for recycling metals, comprising melting used metals in an electrolytic bath, placing a cathode near the electrolytic bath, and performing molten salt electrolysis to obtain fine metal particles.

[7] A method for recycling metal, comprising using used metal as an anode material, placing a cathode near an electrolytic bath and performing molten salt electrolysis to obtain fine metal particles.