JPH06128785A - Production of samarium metal or samarium alloy - Google Patents

Abstract

PURPOSE:To efficiently and stably produce samarium metal or samarium alloy by using the molten salt electrolytic bath containing samarium difluoride and performing electrolytic reduction using samarium oxyfluoride as a starting material. CONSTITUTION:The samarium compd. as the starting material is subjected to electrolytic reduction using the molten salt electrolytic bath consisting essentially of more than 1 kind fluoride of alkali metal or alkaline earth metal and samarium fluoride. At that time, as the samarium fluoride forming the electrolytic bath, samarium difluoride is used. On the other hand, as the samarium compd. of the starting material, samarium oxyfluoride is used. The concn. of the samarium oxyfluoride in the bath is 0.1-10wt.% preferably, and the temp. of the electrolytic bath is in the range of solidus-1000 deg.C preferably. The part in contact with the electrolytic bath of a electrolytic cell is made of iron, and the part for retaining formed samarium metal or samarium alloy is made of hardly fusible metallic crucible of W and Ta, etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a new and useful method for producing samarium metal or samarium alloy. Increasing demand in the magnet industry for metallic samarium, and especially the excellent magnetic properties of alloys with iron, have recently led to the discovery of new magnets such as the so-called Nitro Magne (Sm-Fe-N) magnetic materials. It is expected that the number of uses will increase.

[0002]

2. Description of the Related Art Conventionally, the production of samarium alloys has been carried out by a method of producing metal samarium by a thermal reduction method of reducing samarium oxide with misch metal, and then mixing and melting it with various metals to form an alloy. . Thermal reduction method is 130
Since it is a batch system in which a reduction reaction is carried out at a high temperature of 0 to 1600 ° C. and distillation is carried out, the crucible material is heavily consumed, and the operation is complicated, resulting in a problem of high manufacturing cost.

On the other hand, as another manufacturing method, electrolysis of samarium oxide by a molten salt electrolysis method has been attempted.
Although samarium alloy is produced, the solubility of samarium oxide is low, so that undissolved raw material put into the bath solidifies and deposits, and troubles have not yet occurred until industrial production.

[0004]

It has been conventionally said that the production by the electrolytic method has not been successful because samarium and an electrolyte react with each other (Japanese Patent Publication No. 4517064/1985). A method using an alloyable cathode has been proposed (the same publication). However, in this method, since samarium oxide is used as a raw material,
The solubility of the raw material is poor, and the amount of metal produced is small, so it has not been industrially adopted. Furthermore, in this method, samarium trifluoride, which is a component of the electrolytic bath, is 500
Since a crystal phase transition occurs in a temperature range of up to 600 ° C., there is also a problem that the electrolytic cell is destroyed due to the rapid expansion of the bath when the temperature is lowered such as when the electrolytic cell is stopped.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above-mentioned circumstances, and as a result, samarium oxyfluoride having a high solubility is used as a raw material instead of samarium oxide, and fluoridation for forming an electrolytic bath is further performed. By adopting samarium difluoride as samarium, homogenization of the electrolytic bath is achieved, and only raw material samarium oxyfluoride having a lower electrolytic potential is electrolyzed, and the samarium metal produced is samarium difluoride which is a bath. It was found that a samarium metal or a samarium alloy can be efficiently and stably obtained without being oxidized and consumed, and the present invention has been completed.

That is, an object of the present invention is to provide a method capable of efficiently reducing samarium oxyfluoride to samarium metal or a samarium alloy by a molten salt electrolysis method, capable of continuous operation, and industrially advantageous. is there. Therefore, an object of the present invention is to use a molten salt electrolytic bath mainly containing samarium fluoride and one or more kinds of fluorides selected from the group consisting of alkali metal and alkaline earth metal fluorides, In a method of producing samarium metal or samarium alloy by electrolytic reduction using a samarium compound as a raw material, samarium difluoride is used as samarium fluoride forming an electrolytic bath, and samarium oxyfluoride is used as a samarium compound as a raw material. Can be achieved by

The present invention will be described in detail below. The electrolytic bath used in the present invention is mainly composed of at least one of an alkali metal fluoride and an alkaline earth metal fluoride and samarium fluoride, and the ratio thereof is appropriately selected, but usually, It may be selected from the range of 10 to 95% by weight of samarium fluoride and 90 to 5% by weight of fluoride of alkali metal and / or alkaline earth metal with respect to the entire electrolytic bath. In the present invention, it is important to use mainly samarium difluoride as the samarium fluoride forming the electrolytic bath, and usually 90% by weight or more of the samarium fluoride is samarium difluoride. It is preferable. As the alkali metal and / or alkaline earth metal fluoride, an alkali metal fluoride is generally preferred, and lithium fluoride is most typically used. Further, in the present invention, two or more kinds of alkali metal fluorides and alkaline earth metal fluorides may be used in combination, and specific examples thereof include:
For example, a combination of at least one of barium fluoride, calcium fluoride, and lanthanum fluoride with lithium fluoride can be used.

Samarium difluoride is usually mixed with samarium trifluoride and samarium metal, and then 1,000 to 1,
It can be obtained by reacting at a temperature of 400 ° C. in an argon gas atmosphere. This operation is preferable because the melting temperature can be lowered and the reaction can be carried out at a low temperature when lithium fluoride, which is a bath material, is allowed to coexist. Specifically, after measuring and mixing samarium trifluoride, samarium metal and lithium fluoride so as to obtain a desired bath composition, 800-
A desired electrolytic bath can be directly prepared by reacting at a temperature of 900 ° C. in an argon gas atmosphere.

On the other hand, in the present invention, it is essential to use samarium oxyfluoride as a compound of samarium used as a raw material. As samarium oxyfluoride, there are divalent samarium and trivalent samarium. Usually, the trivalent samarium represented by SmOF is preferable.
In the present invention, good electrolysis can be performed by combining samarium difluoride forming the electrolytic bath and samarium oxyfluoride as a raw material.

The concentration of samarium oxyfluoride as a raw material in the electrolytic bath is usually 0.1% by weight or more and 10% by weight or less, but substantially 1 to 3% by weight is preferable.
If it exceeds 10% by weight, it will not dissolve in the bath and may be deposited, which is not preferable. As the anode used for electrolysis,
Any conventionally used anode can be used, and for example, carbon, platinum, tungsten, tantalum, or the like can be used. Usually, when rod-shaped or plate-shaped carbon is used, a non-consumable anode such as platinum can be obtained. It is cheaper than the conventional method and the voltage used can be lowered. Further, as the cathode, when obtaining a samarium alloy, theoretically, among those that can be alloyed with samarium, the melting point of the metal itself is higher than the temperature of the bath, and the melting point of the alloy with samarium is lower than the temperature of the bath. In practice, iron, cobalt, etc. are usually used. These metals are also raw materials for magnets, and the obtained alloy can be used as it is as a raw material for magnets, which is convenient. Impurities in the cathode are mixed in the alloy, so electrolytic iron or the like containing few impurities is used. In the present invention, the samarium alloy produced in the liquid state on the cathode of these metals,
Drop by the difference in specific gravity from the electrolytic bath. The dropped samarium alloy is stored as a liquid layer in a receiver having an opening in an electrolytic bath below the cathode. Tantalum or tungsten, which are refractory metals, are used as the receiver. Further, the samarium content in the samarium alloy produced in the present invention is usually 60% by weight or more, and specific examples of the alloy include, for example, samarium 60 to 90% by weight, iron 40 to 10% by weight, samarium 60. ~ 90 wt%, nickel 40 ~ 10 wt%
Samarium 60-90% by weight, cobalt 40-
10% by weight, and the like.

When samarium metal is obtained as a simple substance, any material that does not react with samarium or alloys as a cathode can be used, and carbon rods, platinum, etc. can be used, but they are inexpensive. It can be used with a carbon rod without any problems. Depending on the bath composition (such as the ratio of other fluorides such as samarium difluoride / lithium fluoride), the phase state of the electrolytic bath may be either the solid phase and the liquid phase coexisting, or the liquid phase only. It may be in a temperature range in which the liquid phase necessary for the above exists. That is, 100 above the solidus of the phase diagram
The target alloy can be produced within the range of 0 ° C or lower. However, alloys can be obtained even at temperatures above 1000 ° C., but due to the high temperature, disadvantages such as increased evaporation loss of the bath, deterioration of furnace material and heat loss are not preferable.

The voltage between the electrodes is usually 1.5-10 volts,
A low voltage of 1.8 to 5 volts is preferable. Among these voltages, the theoretical decomposition voltage is the minimum required, but if the voltage is higher than necessary, not only heat loss will occur as Joule heat, but also the fluoride in the electrolytic bath will be decomposed, thus saving energy,
It is not preferable in terms of resource saving. The container used for electrolysis is
It is preferable from the economical point of view that the part in contact with the electrolytic bath is made of iron and the part for accumulating the samarium alloy is a metal crucible such as tungsten or tantalum. Conventionally, electrolysis was carried out using expensive materials such as tungsten and tantalum which are infusible noble metals, but in the method of the present invention,
The basic material of the electrolytic cell can be made of inexpensive iron. It was found that the bath used in the present invention had high bath resistance and was sufficiently put to practical use. However, the material for accumulating the samarium alloy is preferably made of a material such as tungsten or tantalum which is a refractory noble metal for the purpose of preventing reaction with the metal.

[0013]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 2,106 g of lithium fluoride and 2,808 samarium trifluoride so that the composition of the electrolytic bath was 35.5 wt% lithium fluoride and 64.5 wt% samarium difluoride.
g, 1,018 g of samarium metal, and after mixing, 900 ° C. in an atmosphere of argon in a tantalum crucible.
In was heated for 2 hours LiF-SmF ₂ electrolytic bath 5,932g
Got Raw material samarium oxyfluoride (SmO
F) is a mixture of samarium oxide (Sm ₂ O ₃ ) powder 349g and samarium trifluoride (SmF ₃ ) powder 207g in an agate mortar, followed by heating in an argon atmosphere in a tantalum crucible at 1100 ° C. for 5 hours. I got it.

The above LiF-SmF ₂ electrolytic bath 5,932 g
Tantalum crucible (inner diameter = 130 mm, depth = 200 m
m). The entire cell was externally heated under an argon atmosphere, and the bath temperature was maintained at 890 to 900 ° C during the electrolysis.
Plate-like electrolytic iron was used for the electrode for the cathode, and plate-like carbon was used for the anode. The distance between both electrodes was 40 mm. A direct current of 50 A was applied for 2 hours for electrolysis. During energization, the raw material samarium oxyfluoride powder is energized at the start of energization
g, after 30 minutes 60 g, after 1 hour 60 g, total 180 g, added to the electrolytic bath. Both the cathode and anode current densities are 1 A /
cm ² and the voltage between the electrodes showed 1.8-4 volts.

After the electrolysis was stopped, the metal accumulated at the bottom of the crucible was 160 g. As a result of analysis, this metal was found to be S.
The alloy was m / Fe = 85/15 (weight ratio). Therefore, the summary metal produced by electrolysis is 136g,
A current efficiency of 73% was obtained. Both the cathode and the anode were worn out. This indicates that the electrolysis of samarium oxyfluoride was normally performed.

On the other hand, for the purpose of selecting the material of the electrolytic cell,
In another furnace, a pure iron crucible of the same size as the tantalum crucible with the tantalum crucible built into the metal reservoir was charged with 6,000 g of the electrolytic bath of the above composition, and 50 g of the above alloy was placed in the inner crucible. Was charged. In this container, the part in contact with the electrolytic bath is made of iron, and the part in which the samarium alloy is stored is tantalum metal. After continuously maintaining at 900 ° C. for 90 days in an argon atmosphere and then cooling and observing the pure iron crucible and the tantalum crucible, no remarkable deterioration was observed in both crucibles.

Comparative Example 1 2,106 g of lithium fluoride and 3,826 g of samarium trifluoride so that the composition of the electrolytic bath was 35.5% by weight of lithium fluoride and 64.5% by weight of samarium trifluoride.
Was weighed and mixed, and then electrolysis was performed in the same manner as in Example 1 except that the cells were placed in an electrolysis cell. After the electrolysis was stopped, the crucible was cracked. No metal accumulated at the bottom of the crucible
It was g. Neither the cathode nor the anode was consumed. The current efficiency was 0%. It can be seen that the target samarium alloy is not formed because samarium difluoride is not contained in the electrolytic bath composition.

Comparative Example 2 Electrolysis was performed in the same manner as in Example 1 except that samarium oxide (Sm ₂ O ₃ ) was used instead of samarium oxyfluoride as a raw material. After the electrolysis was stopped, the amount of metal accumulated at the bottom of the crucible was 50 g. The current efficiency was 23%. In short, it is clear from this that the raw material samarium oxide is not sufficiently dissolved in the bath during electrolysis, and the current efficiency cannot be increased. (That is, in Example 1, it can be seen that samarium oxyfluoride was smoothly dissolved in the bath and electrolyzed.)

[0019]

INDUSTRIAL APPLICABILITY In the present invention, a samarium alloy can be stably and continuously and efficiently manufactured by electrolyzing samarium oxyfluoride as a raw material using a specific electrolytic bath material.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeru Tonohira 1-1 Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu City Mitsubishi Kasei Co., Ltd. Kurosaki Plant

Claims (4)

[Claims] 1. A samarium compound is prepared by using a molten salt electrolytic bath mainly containing samarium fluoride and one or more kinds of fluorides selected from the group consisting of alkali metal and alkaline earth metal fluorides. As a raw material, in a method for producing a samarium metal or a samarium alloy by electrolytic reduction, samarium difluoride is used as samarium fluoride forming an electrolytic bath, and samarium oxyfluoride is used as a samarium compound as a raw material. A method for producing samarium metal or samarium alloy. 2. The method according to claim 1, wherein the concentration of samarium oxyfluoride as a raw material in the electrolytic bath is 0.1% by weight or more and 10% by weight or less. 3. The temperature of the electrolytic bath is 1000 ° C. above the solidus.
The manufacturing method according to claim 1 or 2, which is in the following range. 4. The electrolytic cell as set forth in claim 1, wherein the portion in contact with the electrolytic bath is made of iron, and the portion for accumulating samarium metal or samarium alloy has a refractory metal crucible such as tungsten or tantalum. Manufacturing method.