JPH04202016A - Production of zirconium oxide-based fine powder - Google Patents

Abstract

PURPOSE:To uniformly control compsn. and particle diameter and to improve dispersibility by maintaining a constant concn. of a precipitate and a constant pH when a mixed aq. soln. contg. salts of Zr, Y, Ca, etc., is allowed to react with an alkali soln. and Zr oxide-based fine powder is produced from the resulting precipitate. CONSTITUTION:A mixed aq. soln. contg. water-soluble salts of Zr and one or more among Y, Ca, Mg and Ce is prepd. and allowed to react with an alkali soln. to form a precipitate. At this time, a constant pH is maintained in the reaction system and the constant concn. of the precipitate in the system is maintained from the beginning of the reaction to the end. The resulting precipitate is separated, dried and fired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing high-purity zirconium oxide-based fine powder whose composition and particle size are uniformly controlled and which has excellent dispersibility.

Zirconium oxide powder is used as abrasive materials for weak electric currents, optical lenses,
Used in sintered bodies for forming thin films, special refractories, and toughness-enhancing materials. The zirconium oxide powder used for these purposes must: (1) have a uniform composition; and (2) be small in size.

Various characteristics are required, such as (1) uniform particle size, good dispersibility of zero particles, and (2) high purity.

[Prior Art] As a method aimed at producing zirconium oxide fine powder with a relatively uniform particle size distribution, or as a method expected to be effective, a solution adjusted to a predetermined pH value is prepared. A mixed aqueous solution containing at least one of a hezirconium salt and water-soluble salts of yttrium, calcium, and magnesium and an alkaline solution such as aqueous ammonia are each quantitatively fed into the reaction tank to maintain a constant pH in the reaction tank. (Japanese Patent Publication No. 2-8968), a method in which the reaction is carried out while adjusting the amount within the range of A method in which the product is carried out continuously while flowing out (Unexamined Japanese Patent Publication No. 1983
-44718) and the like have been proposed.

[Problems to be Solved by the Invention] However, the present inventors have found that it is not possible to make the composition and particle size distribution of the zirconium oxide powder uniform by simply adjusting the pH of the liquid in the reaction tank and the flow rate of the feed liquid. It was found that the purity of the powder was insufficient and that there was room to further improve the purity of the powder.

The present invention aims to solve the above-mentioned problems, that is, to obtain a highly purified zirconium oxide-based fine powder whose composition and particle size are uniformly controlled and which has excellent dispersibility.

[Means for Solving the Problems] The present inventors achieved the following by carrying out the neutralization precipitate formation reaction while keeping the precipitate concentration and pH constant during the reaction.
It was discovered that the above-mentioned target fine powder could be obtained, and the present invention was completed.

That is, the present invention maintains the pH within the reaction system at a constant value while at least one of a zirconium salt and a water-soluble salt of yttrium, calcium, magnesium, or cerium.
In a method for producing fine zirconium oxide powder by reacting a mixed aqueous solution containing seeds with an alkaline solution to form a precipitate, separating the resulting precipitate, drying, and firing, the method includes: The gist of this invention is a method for producing fine zirconium oxide powder by keeping the precipitate concentration in the system substantially constant throughout the process.

The present invention will be explained in more detail below.

Examples of the mixed aqueous solution containing a zirconium salt and at least one of water-soluble salts of yttrium, calcium, magnesium, and cerium include chlorides, sulfates, and nitrates. Furthermore, examples of the alkaline solution include aqueous solutions of ammonia, sodium hydroxide, potassium hydroxide, and the like.

The reaction according to the present invention can be carried out in either a four-part reaction system or a continuous reaction system, but from an industrial and economic point of view, a continuous reaction system is preferred. Also, are there any special restrictions regarding the type of reaction tank?As the viscosity of the reaction solution increases as the concentration of precipitates increases, it is preferable to use a reaction tank equipped with a stirrer to maintain a uniform mixing state. .

The reaction operation method is as follows. First, before starting the reaction, a suspension consisting of a precipitate and pure water having a predetermined pH, a predetermined concentration, and a predetermined composition is prepared in a reaction tank. [The precipitate prepared in advance in the reaction tank and the precipitate generated in the reaction tank are M(OH)mSMO
(OH)m-2, MOm/2 ・nH2O (M is Zr,
Y, Ca.

Mg and Ceom are the valences of M. ), and in this specification, "precipitate" and "precipitation product" both refer to this substance. A mixed aqueous solution containing a zirconium salt and at least one of water-soluble salts of yttrium, calcium, magnesium, and cerium and an alkaline solution are separately and simultaneously supplied so that the concentration and composition are maintained. The pH, precipitate concentration, and precipitate composition of the suspension in the reaction tank can be adjusted by supplying the above mixed aqueous solution such as zirconium salt with a predetermined constant concentration and constant composition and an alkaline solution with a predetermined constant concentration at a constant flow rate ratio. should be maintained at a constant value. In continuous operation,
The product solution containing the precipitate is continuously extracted using a metering pump or an overflow type so that the amount of the product solution containing the precipitate is constant in the reaction tank. In the case of batch operation, the supply of the raw material liquid is stopped when the liquid in the reaction tank reaches a predetermined amount.

By separating, washing, drying, and calcining the precipitate obtained in this way, the composition and particle size distribution are uniformly controlled, and the precipitate is a highly dispersible product that does not contain cationic or anionic impurities. The purity of zirconium oxide powder can be changed. In addition, by placing a solution with the same precipitate concentration, composition, and pH as in the reaction tank in advance, this can be prevented from occurring immediately after the start of the reaction (immediately after the start of adding the solution). It acts as a buffer against fluctuations in the precipitate concentration and pH of the system or increases in viscosity in the reaction tank caused by slight imbalances in the flow rate, and the concentration and pH substantially decrease from the start of the reaction (immediately after the start of solution addition). A uniform mixing state is maintained at all times, thereby controlling the composition and particle size to be uniform, resulting in a highly purified zirconium oxide-based fine powder with excellent dispersibility.

The precipitate in the product solution is filtered and washed with water, then dehydrated and dried, and calcined in the range of 600 to 1100°C to obtain a fine powder.

Furthermore, there are no particular restrictions on the amount of suspension prepared in advance in the reaction tank, as long as it can be stirred sufficiently. As the suspension prepared in advance in the reaction tank, it is usually sufficient to use the one remaining in the reaction tank at the end of the previous operation (having the same composition as the precipitated product to be obtained). If such a substance is not available, first add an alkaline substance to pure water to adjust the T)H to that used in the actual operation, and add at least one of a zirconium salt and a water-soluble salt of yttrium, calcium, magnesium, or cerium. A mixed aqueous solution containing the alkaline solution and an alkaline solution are supplied such that the composition and supply ratio of both solutions are the same as those of the present invention, until the concentration of the precipitate in the suspension in the reaction tank reaches a substantially steady state. By continuing its supply, the above-mentioned suspension prepared for carrying out the present invention can be prepared.

That is, even if the necessary suspension is not available at the beginning of the practice of the invention, it can be produced in this way, and -
If the suspension is manufactured in this way, even when the operation is terminated due to periodic repairs, the suspension from the reaction tank at the end of the operation can be stored in the storage tank, and from then on, each time the operation is terminated, the suspension will be The preparation of a suspension for carrying out the invention is no longer necessary.

The concentration of the precipitate is not particularly limited, but in order to obtain a highly pure fine powder with uniform composition and particle size and excellent dispersibility, it should be in the range of 10 to 300 g/Ω in terms of oxide. preferable. If the concentration is lower than 10 g/ρ, water etc. in the dried precipitate are removed, which may be the cause, but the powder after firing has a non-uniform composition and particle size.
It tends to become a fine powder with poor dispersibility and purity, and 30
If it exceeds 0 g/Ω, the viscosity of the product solution containing the precipitate will be high and the fluidity will be poor, making it difficult to obtain a fine powder with uniform composition and particle size, good dispersibility, and high purity.

The pH is preferably selected from the range of 7.0 to 13.0, which is a precipitate-forming region of one precipitate product.

When the pH is lower than 7, it becomes difficult to obtain a 1" precipitated product, and when it exceeds 13, it becomes difficult to remove water, hydroxide, etc. from the precipitate, which is thought to be the cause. It becomes difficult to obtain a fine powder with uniform composition and particle size, good dispersibility, and high purity.

[Function] In the conventional method in which the pH of the reaction solution and the supply flow rate of the raw material solution are kept constant, a mixed aqueous solution containing a zirconium salt and at least one of water-soluble salts of yttrium, calcium, magnesium, and cerium is mixed with an alkali. Since the reaction with the solution is started in the absence of a precipitate, which is a product, in the reaction system, the neutralization precipitate formation reaction occurs locally within the reaction tank, resulting in a pH distribution within the reaction system. However, since the precipitated products are generated depending on the pH, the composition becomes non-uniform. On the other hand, if the reaction is started in the absence of the product, the precipitate, in the system,
The concentration of the precipitate in the reaction solution increases continuously until it reaches a steady state. The particle size of the produced precipitate depends on this precipitate concentration. Therefore, in the conventional method described above, the particle size distribution of the produced precipitate becomes broader (and, as a result, the target zirconium oxide powder) It is estimated that this will make the particle size distribution non-uniform.

Furthermore, when the concentration is low immediately after the start of the reaction, the neutralization precipitate formation reaction occurs locally in lumps in the reaction tank, which not only makes the particle size uneven, but also causes severe aggregation. Impurity anions and cations in the liquid are incorporated into this aggregate, resulting in poor purity of the resulting zirconium oxide powder.

In the present invention, since a precipitate is allowed to exist in the system from the start of the reaction and the concentration of the precipitate is kept constant during the reaction, it is presumed that all of the drawbacks of the conventional methods described in section 2 can be overcome.

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to obtain a highly pure zirconium oxide-based fine powder whose composition and particle size are uniformly controlled and which has excellent particle dispersibility.

Examples] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 In a reaction tank with a volume of 5Ω up to the overflow outflow pipe, the concentration of the precipitate Zr020 Y2O3 equivalent concentration 100g/Ω (
A suspension (containing 3.0 mol 26 of Y2O2) with a pH of 9 was added and stirred. This precipitate suspension was placed in a stirred reaction tank with 1.0% zirconium oxychloride. ．． 54moρ/Ω
At the same time, a mixed aqueous solution of yttrium chloride 0°10m0Ω/β was started to be supplied at 42rrl/min and ammonia water with a concentration of 9.1wt% was started to be supplied at a flow rate of 42mΩ/min using a constant flow pump. The neutralization and precipitation reaction was carried out continuously for 2.6 hours using an overflow method in which the solution was flowed out at a rate of 84 mg/min in terms of raw material solution. The solution in the reaction tank had a precipitate concentration of 100 g/Ω in terms of ZrO2 + Y2O3 - the precipitate in the effluent was separated and washed with water to remove ammonium chloride. A total of 5 points at 3 points immediately after the start of the reaction operation, immediately before the end of the reaction operation, and at equal intervals during the reaction operation time
After drying the precipitate sample at 110°C for 24 hours, it was calcined at 850°C for 1 hour, and the average particle size was determined to be 2.05 to 2.12μ by a light transmission type ultracentrifugal particle size distribution δ111 determination device.
m1 particle size range 1.

87-90% in the range of 0.00-3.00 μm, particle size distribution width 0.60-4.00 μm, specific surface area 16 m
2/g and the purity of Zr○2+Y2O3 is 99
．． 9wt% or more, Y203/Zr○2+Y
Itria partially stabilized zirconia fine powder containing 3.0 mol % of 2O3 was obtained.

Example 2 In the reaction tank, the concentration of the precipitate in terms of ZrO2+cao was 50 g.
/ρ (containing 8.0 mol% as CaO), pH 12 suspension 21 was added and stirred. In the reaction tank under stirring of this precipitate suspension, 0.78 moΩ of zirconium oxychloride was added.
/D1 Calcium chloride 0.

07 moΩ/l mixed aqueous solution at 42 mΩ/min and 10.2 wt% ammonia water at 42 mΩ/m
Supply was started at the same time using a constant flow pump at a flow rate of in, and a neutralization precipitation reaction was carried out for 0.6 hours in a batch reaction system. The liquid in the reaction tank has a precipitate concentration of ZrO2+Ca○
Calculated at 50 g/Ω and pH was maintained at 12. The generated precipitate was separated and washed with water to remove ammonium chloride. The precipitate samples in the reaction tank were dried at 110°C for 24 hours at 110°C for 24 hours, and then calcined at 850°C for 1 hour. The average particle size was 2 using a light transmission type ultracentrifugal particle size distribution 'Al11 constant device.

18-2.22μm1 particle size range 1.00-3.00μm
range of 82-85% and particle size distribution width 0.80-
4.00μm, specific surface area 15m2/g and ZrO
2+CaO purity is 99.9wt% or more, CaO/ZrO
A calcia partially stabilized zirconia fine powder containing 2+CaO or 8.0 mol % was obtained.

Example 3 In a reaction tank with a volume of 5 g up to the overflow outflow pipe, a concentration of ZrO2 + MgO of the precipitate was 100 g/Ω (M
A suspension of 5.0 mol % (containing 5.0 mol % as O) and pH 11 was added thereto and stirred. In the reaction tank under stirring of this precipitate suspension, 1.60 mou/fl of zirconium oxychloride was added.
, magnesium chloride 0.

08mof! /Ω mixed aqueous solution at 42 m. Q/min and concentration9. 8 wt% ammonia water at 42 mρ
A constant flow pump starts supplying at a flow rate of / min at the same time, and a part of the reaction liquid flows out from the overflow tube at a rate of 84 mΩ/min in terms of raw material solution. 4. Precipitate formation reaction.
It lasted 6 hours. The liquid in the reaction tank has a precipitate concentration or ZrO
2+Mg○ conversion: 1.00g/f! and pH is 11
was maintained. The precipitate in the overflow effluent was separated and washed with water to remove ammonium chloride.

One sample of the precipitate was obtained from 5 points in total, immediately after the start of the reaction operation, immediately before the end of the reaction operation, and at equal intervals during the reaction operation time.
After drying at 1000℃ for 24 hours, baking at 850℃ for 1 hour to obtain an average particle size of 2.00 to 2.04μm, particle size range of 1゜OO using a light transmission type ultracentrifugal particle size distribution All+ constant apparatus.
~3.00 μm range 86-90% and particle size distribution width 0.80-4.00 μm, specific surface area 15 m2/g and Z r O2 + M g O purity of 99.9
W t% or more, M g O/ Z r O2+ M g
Magnesium partially stabilized zirconia fine powder containing 5.0 mol % of O was obtained.

Comparative Example] Zirconium oxychloride 1.54 moΩ/
Ω, 2.5Ω of a mixed aqueous solution of 0.10 moΩ/Ω of yttrium chloride was added, and while stirring, 15 2.5ρ of aqueous ammonia with a concentration of 9.1 wt% was added to give a precipitate concentration Z r02 + 100 g/ρ in terms of Y2O3 ( Y
A effluent containing 3.0 mol 26 as 2O3 and pH 9 was obtained. The generated precipitate was separated and washed with water to remove ammonium chloride.

After drying this at 110℃ for 24 hours, it was dried at 850℃ for 1
By baking for a time, the average particle size was 4.88 μm as measured by a light transmission type ultracentrifugal particle size distribution analyzer, and the particle size range was 4.00 μm.
~42% in the range of 6.00 μm and particle size distribution width]
, 00-23. Oμm1 specific surface area 9 m 2 / g and purity of ZrO2 + Y2O3 98.6 wt%, as a result of randomly sampling 5 points from the powder and analyzing the composition,
Y2O3/Zr○2+Y20B range or 2.7-3.4
A mole % of Ittria partially stabilized zirconia fine powder was obtained.

Comparative Example 2 In the reaction tank, 1 g of water adjusted to pH 12 with ammonia water
and stirred. Into this reaction tank under stirring, a mixed aqueous solution of 0.78 moρ/-16~Ω of zirconium oxychloride and 0.07 moρ/ρ of calcium chloride was added at 42 mρ/min, and aqueous ammonia with a concentration of 10.2 wt% was added at 42 mρ/min. Supply was started at the same time using a constant flow pump at a flow rate of 1/min, and a neutralization precipitation reaction was carried out in a batch reaction system for 0.8 hours.

The pH of the liquid in the reaction tank was maintained at 12, and the precipitate concentration at the end of the reaction was 40 g/ρ (C
a content of 8.0 mol% as O).

The generated precipitate was separated and washed with water to remove ammonium chloride. By drying this at 110°C for 24 hours and then baking it at 850°C for 1 hour, the average particle size was 3.57 μm as measured by a light transmission type ultracentrifugal particle size distribution analyzer.
m and particle size range3. 52% in the range 00-5,00 μm and particle size distribution width 1.00-20.0 μm, specific surface area 11 m2/g and ZrO20Y2
03 purity or 98°9 wt%, 55% randomly from the powder
As a result of point sampling and composition analysis, CaO/Z
r O2+ Ca O range is 7.7 to 8.3 mol96
Calcia partially stabilized zirconia fine powder was prepared by IJ.

Comparative Example 3 In a reaction tank with a volume of 5 g up to the overflow pipe, 2 g of water adjusted to pH 11 with aqueous ammonia was placed and stirred. In this reaction tank under stirring, 1.60 moρ/β of zirconium oxychloride and 0.08 moΩ of magnesium chloride were added.
/Ω mixed aqueous solution at 42 mg/min and ammonia water at a concentration of 9.8 wt% at 42 mg/min.
At the same time, supply was started at a constant flow rate of
4.6 due to overflow one-way system that flows out at a rate of n
The neutralization precipitation reaction was carried out continuously over time. The pH of the liquid in the reaction tank was maintained at 11, and the precipitate concentration at the end of the reaction was Z
r O2 + M g O conversion 97.5 g/ρ (M g
The content was 5.0 mol% as O). The precipitate in the overflow effluent was separated and washed with water to remove ammonium chloride. After drying this at 110°C for 24 hours, it was baked at 850°C for 1 hour to obtain an average particle size of 4.28ttm as measured by a light transmission type centrifugal particle size distribution analyzer.
and those with a particle size range of 3.00 to 5.00 μm 5
8% and particle size distribution width 1.00-22.08 m1 specific surface area 9 m2/g and Z r O2+ M g
The purity of O is 99.0 wt%, and as a result of randomly sampling 5 points from the powder and analyzing the composition, M g O / Z r
A partially stabilized ittria-stabilized zirconia fine powder containing 4.8 to 5.3 mol% of 02+MgO was obtained.

Claims (1)

[Claims] (1) While maintaining the pH in the reaction system at a constant value, a mixed aqueous solution containing a zirconium salt and at least one of water-soluble salts of yttrium, calcium, magnesium, and cerium is reacted with an alkaline solution to precipitate. In the method for producing fine zirconium oxide powder by separating, drying, and calcining the resulting precipitate, the precipitate concentration in the system is kept substantially constant from the start to the end of the reaction. A method for producing zirconium oxide-based fine powder.