JPS60137827A - Production of fine zirconia powder - Google Patents

Abstract

PURPOSE:To produce fine zirconia powder, containing a uniformly dispersed stabilizer, and having a large specific surface area without requiring a pulverizing operation, by mixing aqueous solutions of raw materials in the presence of a surfactant and a water-insoluble organic solvent, and reacting the raw materials. CONSTITUTION:A surfactant, e.g. a nonionic surfactant having about 4-20HLB, a water-insoluble organic solvent, e.g. benzene, and water are previously charged into a reaction vessel. An aqueous solution containing about 20-60wt% zirconium salt, e.g. zirconium oxychloride octahydrate, and about 0.5-6wt% stabilizer, e.g. a water-soluble yttrium salt, and an aqueous solution containing about 5- 30wt% ammonium carbonate are added thereto and strongly stirred. The resultant carbonate is then washed with a water-soluble organic solvent, e.g. acetone, dried and fired at about 600-1,000 deg.C in the atmosphere of air to afford the aimed fine powdery zirconia.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine zirconia powder, in which the powder has a large specific surface area, an extremely small particle size, and is independent grains without requiring any pulverization operation. The present invention provides a method for producing easily sinterable high-purity zirconia fine powder in which a stabilizer is uniformly dispersed.

Zirconia powder is used as a raw material for sintered products, but in order to be applied to fields that require high toughness, such as for mechanical structures, it must (1) be a high-purity product;
(2) It is a fine powder consisting of independent homogeneous grains, (3)
It is desired that the stabilizer be uniformly and homogeneously dispersed.

However, conventional methods for producing zirconia powder (melting method, neutralization method, etc.) require mechanical pulverization to produce a powder, resulting in low purity and large particle sizes even after pulverization, resulting in sintering. It had the disadvantage that it had poor condensation properties and that the stabilizer was not homogeneously dispersed.

The present inventors completed the present invention as a result of intensive research aimed at solving these conventional disadvantages.

That is, in the present invention, an aqueous solution containing a zirconium salt and a stabilizer and an aqueous ammonium carbonate solution are mixed with stirring in the presence of a surfactant and a water-insoluble organic solvent, and the reaction is carried out while maintaining the reaction system in an emulsified state. The present invention relates to a method for producing fine zirconia powder, which comprises washing the produced carbonate with a water-soluble organic solvent and then thermally decomposing it. This will be explained in detail below.

The zirconium salt used as a raw material in the present invention is usually water-soluble, such as zirconium oxychloride octahydrate or zirconium sulfate. Such stabilizers include those already known, such as calcium and magnesium.

Water-soluble materials such as gnesicium, cerium, and metals having a valence of 3 or more (yttrium, diisprosium, erbium, ytterbium, etc.) are used. By preparing a mixed aqueous solution of the zirconium salt and the stabilizer, the stabilizer can be mixed uniformly. There are no particular restrictions on the concentration of this mixed aqueous solution, but it is usually 20 to 60% by weight of the zirconium salt and 0.5 to 6% by weight of the stabilizer.
And it is sufficient.

On the other hand, an ammonium carbonate aqueous solution is prepared, and the concentration of this solution may be approximately in the range of 5 to 30% by weight.

By mixing the aqueous solution containing the zirconium salt and stabilizer with the ammonium carbonate aqueous solution, zirconium and the stabilizer carbonate are produced.In the present invention, this reaction is carried out using a surfactant and a water-insoluble organic solvent. is required to be carried out in the presence of i.e. 1
Carbonate is generated while maintaining the reaction system in an emulsified state.

It is recommended that the surfactant and water-insoluble organic solvent be added to the reactor together with water at the start of the reaction, but if the reaction is to be carried out continuously, an aqueous solution containing the zirconium salt and stabilizer should be added to the reactor. A method is adopted in which, simultaneously with the continuous charging of the ammonium carbonate aqueous solution, a water-insoluble organic solvent solution in which a predetermined amount of a surfactant is dissolved is introduced into the reactor from a separate line. At this time, the reaction mixture is taken out from overflow C2.

By maintaining the reaction system in an emulsified state as described above, it is possible to obtain finely powdered zirconia in which the stabilizer having a larger specific surface area is uniformly dispersed. Among nonionic surfactants, those having an HLB value of 4 to 20 are particularly suitable as surfactants used for this purpose. Benzene, toluene, xylene, etc. are used as water-insoluble organic solvents.

It is preferable to stir the reaction system strongly using a homomixer, homogenizer, etc. If the stirring is weak, fine powdered zirconia cannot be obtained.

Next, the generated carbonate is washed with a water-soluble organic solvent. That is, by this washing, the water adhering to or penetrating the carbonate is replaced with the organic solvent, and then drying is performed. If dried while still containing moisture, carbonate particles will aggregate, making it impossible to obtain easily sinterable fine powder zirconia consisting of independent grains.

The washed carbonate is dried and thermally decomposed to obtain zirconia powder, and this thermal decomposition is usually carried out in an air atmosphere at a temperature in the range of 600 to 1000°C.

Next, I will give a concrete example.

Example 1 Reactor ζ with capacity 307 with in-line homomixer
2. Ammonium carbonate aqueous solution with a concentration of 13.5% by weight s, o
o o), toluene 7.000. P, sorbitan oleate (Nippon Nyukka Warisaki, Newaol 3Q, HLB6
．． 4) 120iP was added and stirring was started.

Rotation speed: 7.0.0 Orpm + After double rotation, a mixed aqueous solution of zirconium salt and yttrium salt (stabilizer) (zirconium oxychloride octahydrate 35.7%, chloride) Jll Lamb, 243% by weight aqueous solution) using a metering pump for 30? At the same time, an aqueous ammonium carbonate solution with a concentration of 13.5% by weight was added from another series at a rate of 40% by weight.
5? / minute, and sorbitan oleate (New
A toluene solution containing 1.7% by weight of co'l 80)
0? They were added continuously at a rate of 1/2 min, and the reaction was carried out while maintaining stirring at the above-mentioned rotational speed. During the reaction, the reaction mixture was discharged from the overflow of the reactor. The overflow from 6 hours to 7 hours and 40 minutes after the start of the reaction was collected and filtered through a vacuum filter, and the cake-like material deposited on the filter was washed with 5 J of acetone and filtered. This cleaning f
After repeating the process three times, the solvent was removed using a vacuum dryer.
After drying, it was fired at 800°C for 1 hour in an air atmosphere, and as shown in Table 1, fine zirconia powder with a large specific surface area, independent grains, and a stabilizer uniformly dispersed was obtained. Obtained.

The X-ray diffraction pattern of this zirconia fine powder was as shown in FIG. 1, and it had extremely good sinterability.

Example 2 In Example 1, polyethylene glycol monostearate (manufactured by Kao Atlas Co., Ltd., Emanone 3199, HLB1) was used instead of sorbitan oleate as an emulsifier.
As shown in Table 1, the stabilizer was in the form of a fine powder consisting of independent grains with a large specific surface area, and the stabilizing agent was uniform. A fine zirconia powder was obtained. This product had extremely good sinterability.

Example 3 In Example 1, instead of yttrium chloride as a stabilizer, a rare earth oxide mixture with an yttria content of 64%, usually called yttria concentrate, was dissolved in hydrochloric acid water, and yttrium chloride was added. 0.795 in concentration
The reaction was carried out in the same manner except that a mixed aqueous solution was used so that the concentration of weight%
, 3.5% by weight each of cerium and gadolinium (and others).

After the reaction, the product was washed and fired in the same manner as shown in Table 1. As shown in Table 1, a fine zirconia powder having a large specific surface area and consisting of independent grains in which the stabilizer was uniformly dispersed was obtained. This product had extremely good sinterability.

Comparative Example 1 The reaction and washing were carried out in the same manner as in Example 1 except that no surfactant and water-insoluble organic solvent were used.
When dried and thermally decomposed, the results shown in Table 1 were obtained. Furthermore, when the zirconia powder obtained in this comparative example was examined using an electron microscope photograph, it was found that the average particle diameter was approximately 5 μm.
Met.

Comparative Example 2 When Example 1 was carried out in the same manner as in Example 1 except that no acetone washing was performed, the results shown in Table 1-62 were obtained.

[Brief explanation of drawings]

FIG. 1 shows an X-ray diffraction pattern of the zirconia powder obtained in Example 1. Patent applicant Shin-Etsu Chemical Co., Ltd.□20

Claims (1)

[Claims] 1. An aqueous solution containing a zirconium salt and a stabilizer and an aqueous ammonium carbonate solution were mixed with stirring in the presence of a surfactant and a water-insoluble organic solvent, and reacted while maintaining the reaction system in an emulsified state. A method for producing fine zirconia powder, which comprises washing carbonate with a water-soluble organic solvent and then thermally decomposing it.