JPH052722B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing rare earth metal powder,
More specifically, the present invention relates to an industrial method capable of producing fine rare earth metal powder with high purity.

[Conventional technology]

Alloys containing one or more rare earth metals (including intermetallic compounds) include permanent magnet materials, magnetostrictive materials, magnetic sensors, magnetic refrigeration materials, magneto-optical recording materials, hydrogen storage alloys, superconducting materials, heat-resistant and corrosion-resistant metals. It is known that it is useful as a functional material such as a high-strength metal material.

Rare earth metals used as main components or additives in such alloys are processed by molten salt electrolysis (mainly La, Ce, Pr, Nd and Mitsushimetal, which is an alloy of these metals), vacuum reduction method of oxides (Sm, Eu, Tm, Yb, etc.), thermal reduction method of halides (rare earth metals other than Sm, Eu, Tm, Yb), etc. Manufactured.

[Problems to be Solved by the Invention] By the way, the rare earth metal produced by the above production method is obtained in the form of an ingot, but since rare earth metals are generally highly active towards oxygen and water,
Stored as an ingot in an inert atmosphere, in vacuum or in oil. Therefore, in order to produce rare earth metal powder, it is necessary to crush this ingot in a state where it is shielded from oxidizing substances such as air and water, for example in an organic solvent. In other words, when rare earth metal ingots are crushed in the presence of O ₂ or water, the oxide film that has formed on the surface of the rare earth metal particles is polished away and oxidation progresses. Since oxidation is accelerated due to the temperature increase due to the heat generated, the entire rare earth metal is easily oxidized. Therefore, methods such as pulverizing rare earth metals in the form of ingots in organic solvents are technically and economically inappropriate as industrial production methods, and rare earth metal powders have traditionally been produced industrially. was not manufactured.

The purpose of the present invention is to solve the above-mentioned conventional problems,
An object of the present invention is to provide an industrial method for producing rare earth metal powder.

[Means for solving problems]

That is, in order to solve the above problems, the present invention provides a method in which a mixture of a rare earth oxide powder, a reducing agent, and an alkali metal or alkaline earth metal chloride is heated in an inert atmosphere or under vacuum. Thereafter, a method for producing rare earth metal powder is provided, which comprises wet-processing the resulting mixture.

In the present invention, rare earth elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gatlinium (Ga), terbium (Tb),
Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu), Promethium (Pm),
Includes yttrium (Y) and scandium (Sc).

The rare earth oxide used in the method of the present invention may be any of the above-mentioned rare earth metal oxides, and may be one type alone or a combination of two or more types.

Furthermore, the particle size of the rare earth oxide powder is a factor that determines the particle size of the rare earth metal powder obtained as a product, so it should be appropriately selected depending on the required particle size of the rare earth metal powder. For example, in order to obtain fine rare earth metal powder, the particle size of the rare earth oxide powder used must be fine.
Generally, an average particle size (based on the subsieve sizer method (Fsss), the same applies hereinafter) of 1 to 50 μm is preferable.

In addition, the reducing agent used in this method is
Alkali metals, alkaline earth metals or their hydrides and mixtures thereof can be used. Examples of alkali metals and their hydrides include lithium, sodium, potassium, etc., and their hydrides; examples of alkaline earth metals and their hydrides include magnesium, calcium, etc., and their hydrides. However, from the viewpoint of handling safety and cost, magnesium, calcium, and especially calcium and its hydride are preferred.

There are no particular restrictions on the shape of these reducing agents, and commercially available granular or flaky ones are not used;
It is used in an amount that is 1.1 times or more the reaction equivalent (the stoichiometric amount required to reduce the rare earth oxide).

Furthermore, the chlorides of alkali metals or alkaline earth metals include sodium, potassium,
Examples include chlorides of lithium, magnesium, calcium, etc., and anhydrous ones containing no hydrates are preferred. Further, anhydrous calcium chloride is particularly preferred since it exhibits almost no volatility when heated and is advantageous in terms of cost. The shape of these alkali metal or alkaline earth metal chlorides is not particularly limited, and for example, powder or flake forms can be used, and the amount used is 1% by weight or more based on the amount of rare earth oxide. In particular, it is preferably 5 to 20% by weight. If the amount is too small, there will be no effect of promoting the disintegration of the product mixture obtained as an agglomerate as described later, and even if it exceeds 20% by weight, no further effect can be expected, which is economically disadvantageous.

In the method of the invention, a mixture of rare earth oxide powder, reducing agent and the chloride is first prepared, preferably under anhydrous conditions.
That is, anhydrous and dry raw materials are used, and these are mixed in a dry, inert atmosphere to avoid moisture absorption. Examples of the inert atmosphere include argon, nitrogen, and the like.

The resulting mixture is then heated under an inert atmosphere or vacuum. As the inert atmosphere used, argon, nitrogen, etc. can be mentioned as mentioned above. Also, the heating temperature at this time is 800~
The temperature is preferably 1,300°C, particularly in the range of 950 to 1,200°C, and the heating time is not particularly limited, and the heating may be performed for a period of time necessary to obtain a uniformly reduced metal powder. The heat treatment is usually carried out by charging the mixture into a reaction vessel made of a material with high heat resistance (for example, made of stainless steel), and there is no particular restriction on the rate of temperature increase during heating. When the mixture temperature rises above about 700°C, a rapid temperature increase generally occurs due to a thermal reduction reaction. This rapid temperature increase ends in about 5 to 15 minutes. Most of the rare earth oxide is reduced to metal during this time. Then, to complete the reaction,
Hold at 800°C to 1300°C for desired time. If the heating temperature is less than 800℃, the reduction rate of rare earth oxides will be slow and the treatment will take a long time. If the heating temperature is higher than 1300℃, the chloride will volatilize and escape, resulting in the resulting mixture being strongly sintered. , the resulting product mixture agglomerates are less likely to be broken up by subsequent wet processing. After the reaction is complete, the product mixture in the reaction vessel is cooled under an inert atmosphere. The product mixture thus obtained is an agglomerate consisting of rare earth metal particles, residual reducing agent and chloride, and a by-product alkali metal or alkaline earth metal oxide.

The resulting product mixture is then subjected to wet processing. The wet treatment here means a treatment in which the resulting mixture is brought into contact with a relatively large amount of water, and is carried out in order to suppress the oxidation reaction due to an increase in liquid temperature. That is, this treatment does not mean pulverization treatment in the presence of water. With this level of treatment, only an oxide film is formed on the rare earth metal surface.
Such an oxide film can be easily removed by dilute acid treatment or the like, if necessary.

Contacting the product mixture with a relatively large amount of water is usually carried out by pouring the product mixture into a relatively large amount of water and stirring if necessary, and does not imply a grinding process in the presence of water. On contact with water, the agglomerates disintegrate with the evolution of H ₂ gas due to the reaction of residual alkali or alkaline earth metals with water. At this time, the by-produced alkali metal or alkaline earth metal oxides are hydrated and eluted or form a suspension. Eluates and suspensions can be separated from rare earth metal particles by decantation. The suspension is completely removed by repeating the watering-stirring-decantation cycle. When the mixture is poured into water and stirred, the amount of water is preferably 4 times or more the amount of the product mixture.
If the amount is smaller than this, the oxidation reaction of rare earth metal particles due to an increase in liquid temperature will occur, and the amount of rare earth metal particles lost as a result of suspension will increase. The obtained rare earth metal powder can be
PH4 by dilute acid, e.g. acetic acid or hydrochloric acid solution
By performing the treatment in steps 7 to 7, the alkali metal or alkaline earth metal component remaining in a small amount and the formed oxide film can be easily removed. Thereafter, it is washed with an organic solvent such as alcohol or acetone, thoroughly dehydrated, and then vacuum dried.

Note that it is also possible to allow it to naturally disintegrate in the air before putting it into water, but care must be taken to avoid oxidation of the generated rare earth metal.

[Effect]

In the method of the present invention, the alkali metal or alkaline earth metal chloride prevents welding of the generated rare earth metal particles and by-produced alkali metal or alkaline earth metal oxides such as CaO in the heat treatment step. . In addition, since the by-product oxide is impregnated with chloride, the agglomerates of the resulting product mixture are easily separated from the rare earth metal particles and the by-product oxide in the subsequent wet treatment. It disintegrates quickly and the resulting metal particles are separated from other unwanted materials. That is, when alkali or alkaline earth metal chlorides are not present, the resulting mixture is difficult to disintegrate, making it difficult to separate and recover the rare earth metal particles.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples. In the following, % means weight %, μm representing particle size is based on the Fsss method, and mesh is based on Tyler.

Example 1 1000 g of gadolinium oxide powder (Gd ₂ O ₃ purity 99.9%, average particle size 10 μm), 100 g anhydrous calcium chloride (1st class reagent, 65 mesh or less), and granular metallic calcium (Mg containing, Ca purity 99.5%, 4 mesh) 496 g (1.5 times the stoichiometric amount) were mixed in an argon atmosphere. Gadolinium oxide and anhydrous calcium chloride have a temperature of 2 to 3 at 100℃ and 400℃, respectively.
I used one that had been dried for a while. The mixture was placed in a stainless steel reaction vessel into which argon gas was flowing, and the temperature was raised from room temperature to 1000°C in 80 minutes, maintained at 1000°C for 1 hour, and then cooled. After cooling, the product mixture was removed from the reaction vessel and poured into 100ml of water. The resulting mixture is accompanied by gas evolution.
It collapsed in 30 minutes. The Ca(OH) ₂ suspension formed in water could be largely removed by decantation. Thereafter, the operations of pouring water, stirring for 1 hour, and decanting were repeated three times. Dilute acetic acid was added dropwise to the resulting solution containing the metal gadolinium powder, and the pH was adjusted to 6.0.
and stirred for 10 minutes. After that, after filtering and washing with water several times with ethanol, 50℃, 0.5Torr.
It was vacuum dried. The average particle size of the obtained metallic gadolinium powder was 15 μm, Ca content 0.05%, O content 0.18
It was %. The yield of gadolinium was 90%.

Example 2 Samarium oxide powder (Sm ₂ O ₃ purity 99%) 1000
g, 50 g of anhydrous calcium chloride, and 447 g (1.3 times the stoichiometric amount) of granular metallic calcium (containing Mg, Ca purity 99.5%, 4 mesh or less) were mixed. The mixture was charged into a stainless steel reaction vessel filled with argon gas and heated from room temperature to 1000℃ for 80 minutes.
The temperature was raised in 1 minute, held at 1000°C for 30 minutes, and then cooled.
After cooling, take out the product mixture from the reaction vessel and add 5
into the water. The resulting mixture disintegrated in 30 minutes. The Ca(OH) ₂ suspension formed in water was removed by repeated decantation several times. The resulting liquid containing samarium metal powder was filtered, washed with ethanol and water several times, and then vacuum-dried at 40°C and 0.1 Torr. The average particle size of the obtained metallic samarium powder was 14 μm, the Ca content was 0.27%, and the O content was 0.15%.

Example 3 1000 g of neodymium oxide (Nd ₂ O ₃ 99.9%) powder, 150 g of anhydrous calcium chloride, and granular metallic calcium (containing Mg, Ca purity 99.5%, 4 mesh or less)
536 g (1.5 times the stoichiometric amount) were mixed. The mixture was charged into a stainless steel reaction vessel into which argon gas was introduced, and the temperature was raised from room temperature to 1000°C in 80 minutes, and maintained at 1000°C for 30 minutes. After cooling, the product mixture was taken out from the reaction vessel and poured into the water in Step 5. The resulting mixture disintegrated in 5 minutes. The Ca(OH) ₂ suspension formed in water was removed by repeated decantation several times. The resulting liquid containing neodymium metal powder was filtered, washed with ethanol several times, and then vacuum dried at 40°C and 0.1 Torr. The average particle size of the obtained metallic neodymium powder was 10 μm, and the Ca content was
The O content was 0.10% and the O content was 0.35%.

Comparative example: 1000 g of cadrinium oxide powder (Gd ₂ O ₃ purity 99.9%, average particle size 10 μm), and granular metallic calcium (Mg content, Ca purity 99.5%, 4 mesh or less)
496 g (1.5 times the stoichiometric amount) were mixed in an argon atmosphere. Gadolinium oxide and metallic calcium were dried at 100°C and 400°C for 2 to 3 hours, respectively. The mixture was placed in a stainless steel reaction vessel into which argon gas was flowing, and the temperature was raised from room temperature to 1000°C in 80 minutes, maintained at 1000°C for 1 hour, and then cooled. After cooling, the product mixture was removed from the reaction vessel and poured into 100ml of water.
The resulting mixture was left in water for 48 hours without much disintegration.

〔Effect of the invention〕

By the method of the present invention, it is possible to industrially advantageously produce rare earth metal powder, which has heretofore been technically and economically difficult to produce industrially. Moreover, the obtained rare earth metal powder has high purity, and it is possible to produce fine particles with an average particle size (Fsss) of 50 μm or less.

In other words, coarsening of the raw material powder during the manufacturing process is suppressed, and the resulting mixture containing metal powder obtained by heat treatment has high disintegration (pulverization) in water, making it easy to produce metal powder with the target particle size. can be manufactured.

The method of the present invention does not require a mechanical pulverization step to obtain rare earth metal powder, and the Ca component can be separated by a short wet process, resulting in a high yield, suitable for mass production, and an industrial manufacturing method. It is excellent as.

Claims (1)

[Claims] 1 Rare earth metal powder made by heating a mixture of rare earth oxide powder, a reducing agent, and an alkali metal or alkaline earth metal chloride in an inert atmosphere or under vacuum, and then wet-processing the resulting mixture. manufacturing method.