JPH08119632A - Production of hydroxide of rare earth element and production of oxide of rare earth element - Google Patents

Abstract

PURPOSE: To easily produce spherical particles of oxide of a rare earth element useful as powder for thermal spraying and bedding powder spread at the time of sintering a ceramic compact. CONSTITUTION: When an aq. soln. of a water-soluble salt of a rare earth element is mixed with an aq. soln. of ammonia or an alkali hydroxide and they are brought into a reaction to form a precipitate of hydroxide of the rare earth element, at least one of the aq. solns. is dispersed in an org. solvent which is not uniformly miscible with water before the mixing and the resultant precipitate is fired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a spherical rare earth element oxide which is useful as a powder for thermal spraying or as a spread powder for firing a ceramics sintered body.

[0002]

2. Description of the Related Art When a sprayed film of a rare earth element oxide is to be produced, it is convenient that the flowability of the powder supplied to the burner is good to obtain a uniform film, and therefore spherical particles are preferred. . In addition, spherical particles that are good in fluidity and require a small contact area are also preferred as the spreading powder to be spread to prevent the adhesion and reaction with the furnace material when sintering the ceramic compact.

Japanese Unexamined Patent Publication (Kokai) No. 3-23214 discloses a method of obtaining spherical particles by granulation using fine powdery rare earth element oxides. In this method, once a precipitate is formed from a solution, filtered, Since the fine particles are produced by firing and then the fine particles are produced, it is troublesome.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide a method for easily producing spherical particles of rare earth element oxides suitable for spraying and spreading powder from an aqueous solution. It is a thing.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to solve such problems, and have a spherical rare earth element oxide suitable for thermal spraying and spread powder which has a high productivity and a simple process. The present invention has been completed by establishing a manufacturing method and establishing manufacturing conditions, and the gist thereof is that an aqueous solution of a water-soluble salt of a rare earth element and an aqueous solution of ammonia or an alkali hydroxide are mixed and reacted. In obtaining a precipitate of a rare earth element hydroxide, at least one of the rare earth element aqueous solution and the alkaline aqueous solution is dispersed and added in an organic solvent that is not uniformly mixed with water. And a method for producing a rare earth element oxide by firing the same.

According to the present invention, a hydroxide can be easily obtained from an aqueous solution of a water-soluble salt of a rare earth element, and a spherical rare earth element oxide in the form of spherical particles can be easily obtained by firing the same, which is economical and It was found that almost all the particles were spherical particles, the angle of repose was small, and the particles were useful as a powder for thermal spraying or a spread powder during ceramic sintering.

Hereinafter, the present invention will be described in detail. The applicable range of the present invention is yttrium as a rare earth element and a lanthanoid having an atomic number of 57 to 71.

The term "spherical" in the present invention means a true sphere and a substantially spherical particle having a ratio of major axis to minor axis of 1.5 or less. This is a sufficient range for use. Further, the oxide composed of such particles has a repose angle (measured by a tilt method) showing good flowability smaller than that of a normal oxide. The average particle size (D ₅₀ ) is expressed on a volume basis, and is 50% of the total particle volume.
Are occupied by particles having an average particle size or less. A Coulter counter (trade name, manufactured by Coulter, Inc.) was used for the measurement method.

As the method for producing the spherical rare earth element hydroxide of the present invention, when the aqueous solution of the water soluble salt of the rare earth element is reacted with the aqueous solution of ammonia or the alkali hydroxide to precipitate the precipitate, the rare earth element aqueous solution is used. And at least one of the alkaline aqueous solutions are dispersed in an organic solvent that is not uniformly mixed with water, and a so-called w / o type emulsion in which an aqueous phase is dispersed in a continuous phase of the organic solvent is added. As the water-soluble salt of rare earth element, nitrate, chloride and the like are used. The rare earth element may be of one type, two or more types,
Further, if the total rare earth element concentration is too low, the liquid amount increases and it is uneconomical. If it is too high, the viscosity increases too much after precipitation is formed, so 0.1 to 2.0 mol / l is preferable.

An aqueous solution of sodium hydroxide, potassium hydroxide, barium hydroxide, or ammonia is used for precipitating the rare earth element, but ammonia water is preferably used when mixing of alkali metals or the like is disliked. This concentration is also 0.2 ~ for the same reason as described in the rare earth element solution.
5.0 mol / l is good. The amount is preferably 3 to 5 mol per 1 mol of the rare earth element, and if the amount is less than 3 mol, the yield is poor and 5 mol.
Even if it exceeds l, it is uneconomical with no effect.

Any organic solvent may be used as long as it does not mix uniformly with water, but examples thereof include aromatic hydrocarbons such as toluene, straight-chain aliphatic hydrocarbons such as n-hexane, and cycloaliphatic hydrocarbons such as cyclohexane. Examples include mixtures obtained by fractional distillation of petroleum such as hydrogen and kerosene. Among them, kerosene, cyclohexane and the like are preferable in consideration of the high flash point, safety to human body, price and the like. The amount used is 2 to 5 times the volume of the aqueous solution to be dispersed.
It is convenient for the production of w / o emulsions.

Further, at this time, sorbitan monooleate,
A relatively oil-soluble emulsifier such as polyoxyethylene sorbitan monostearate or sorbitan trioleate is added in an amount of 0.5 to 5.0% by weight based on the organic solvent.

As a method of mixing the solution, one of an alkali solution and a rare earth element solution to be added as an emulsion is first mixed with an organic solvent in which an emulsifier is dissolved by shaking, stirring or the like to emulsify. Whether or not the w / o emulsion was successfully prepared can be confirmed by a method such as adding an oil-soluble or water-soluble dye with an optical microscope. When both the rare earth element aqueous solution and the alkaline aqueous solution are made into emulsions, the emulsions may be mixed in either order, but when one is mixed only with the aqueous solution, the emulsion is preferably added to the aqueous solution. The time required for this mixing may be arbitrary. The temperature when mixing the solutions is preferably room temperature. Even if the temperature is low, there is no effect, and it is not preferable to increase the temperature because it uses an organic solvent.

When all the solutions have been added, the reaction is allowed to proceed for 10 minutes or more to complete the reaction. When the formation of precipitate is complete, it is filtered off with a Buchner funnel and washed with water. A spherical rare earth hydroxide was thus obtained. The obtained hydroxide is 600
Spherical rare earth element oxides can be obtained by firing at temperatures above ℃ 1,500 ℃.

[0015]

EXAMPLES The embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto. Example 1 To 200 ml of kerosene, 1.5 g of sorbitan monooleate was added and dissolved and placed in a separating funnel. Where 1.5mol / l
80 ml of the yttrium nitrate aqueous solution was added, and the container was sealed and shaken with a shaker to give a w / o emulsion. this is,
The mixture was stirred until the next reaction so as not to separate the phases. Separately, dissolve 1.5 ml of sorbitan monooleate in 200 ml of kerosene, put it in a separatory funnel, add 40 ml of 28% ammonia water and 20 ml of pure water, close the cap, and shake with a shaker. After a w / o emulsion, it was transferred to a 1 liter beaker and stirred with a stirring blade attached to a motor. The above-mentioned yttrium nitrate emulsion was poured into this for 30 seconds. After stirring for a further 30 minutes, it was filtered off with a Buchner funnel. After washing the precipitate with 500 ml of water, place it in a magnetic crucible and place it in an electric furnace in the atmosphere.
The temperature was raised to 900 ° C over 1 hour, kept at 900 ° C for 1 hour, and then allowed to cool. 13.4 g of yttrium oxide was obtained. The average particle size was 22.5 μm, the angle of repose was 39 degrees, and when observed with an electron microscope, almost all were spherical particles.

EXAMPLE 2 An emulsion of an aqueous yttrium nitrate solution produced in the same manner as in Example 1 was prepared by reacting 28% ammonia water with 40 ml and 460 ml without reacting the ammonia water with the emulsion.
While stirring, the mixture was poured into an aqueous solution obtained by mixing pure water of 30. Thereafter, in the same manner as in Example 1, 13.3 g of yttrium oxide was obtained. The average particle size is 14.7 μm,
The angle of repose was 41 degrees, and when observed by an electron microscope, almost all of them consisted of spherical particles.

Example 3 21.5 g of gadolinium oxide was obtained in the same manner as in Example 1 except that a 1.5 mol / l gadolinium nitrate aqueous solution was used instead of the yttrium nitrate aqueous solution. Average particle size is 30.8
The angle of repose was 36 degrees, and when observed by an electron microscope, almost all of them consisted of spherical particles.

Example 4 In the same manner as in Example 1 except that a 1.5 mol / l neodymium nitrate aqueous solution was used instead of the yttrium nitrate aqueous solution,
19.8 g of neodymium oxide was obtained. The average particle size was 25.8 μm, the angle of repose was 38 degrees, and when observed by an electron microscope, almost all were spherical particles.

Example 5 Instead of adding 40 ml of 28% ammonia water and 20 ml of pure water, 1
13.3 g of yttrium oxide was obtained in the same manner as in Example 1 except that 180 ml of a 0 mol / l sodium hydroxide aqueous solution was used. The average particle size was 19.6 μm, the angle of repose was 40 degrees, and when observed by an electron microscope, almost all were spherical particles.

Comparative Example 1 160 ml of a 0.75 mol / l yttrium nitrate aqueous solution was poured over 3 minutes into an aqueous solution obtained by mixing 40 ml of 28% ammonia water and 460 ml of pure water while stirring. Thereafter, in the same manner as in Example 1, 13.5 g of yttrium oxide was obtained.
The average particle size is 51.4 μm, and the angle of repose has extremely poor flowability and cannot be measured. When observed with an electron microscope, in addition to angular irregular-shaped particles, fine particles of 1 to several μm were also seen.

Comparative Example 2 13.3 g of yttrium oxide was obtained in the same manner as in Example 2 except that 25 g of oxalic acid dihydrate was added instead of 28% aqueous ammonia. The average particle size is 5.4 μm, and the angle of repose is extremely poor in flowability and cannot be measured. When observed with an electron microscope,
It consisted of angular irregularly shaped particles. Moreover, when a part of the precipitate before firing was taken and the X-ray diffraction pattern was measured, it was normal yttrium oxalate.

[0022]

INDUSTRIAL APPLICABILITY According to the present invention, spherical particles of rare earth element oxide can be easily obtained. Also, since almost all of them are spherical particles, the angle of repose is small and the powder for spraying or the ceramic sintering is used. It is useful as a spreader for baking the body.

Claims (2)

[Claims] 1. When the aqueous solution of a water-soluble salt of a rare earth element and an aqueous solution of ammonia or an alkali hydroxide are mixed and reacted to obtain a precipitate of a rare earth hydroxide, the aqueous solution of the rare earth element and the aqueous alkali solution. A method for producing a rare earth element hydroxide, characterized in that at least one of the above is dispersed in an organic solvent that is not uniformly mixed with water and added. 2. A method for producing a rare earth element oxide, which comprises firing the rare earth element hydroxide obtained by the method according to claim 1.