JPS60103032A - Manufacture of fine zirconium oxide powder - Google Patents

Abstract

PURPOSE:To manufacture fine zirconium oxide powder having a narrow particle size distribution, high activity and favorable sinterability by drying without requiring a cooling means by placing zirconium hydroxide hydrate in vacuum and carrying out heating after starting freeze-drying. CONSTITUTION:An alkali soln. is added to zirconium oxychloride to form zirconium hydroxide, and this zirconium hydroxide is dried in vacuum. When filtration is carried out in a pretreatment stage, porous porcelain is put on the bottom of a vacuum chamber, and the zirconium hydroxide is allowed to stand in vacuum. It is decomposed into H2O and ZrO2, H2O is vaporized, and cooling proceeds by the latent heat of vaporization, so freeze-drying is carried out. When freezing proceeds excessively to drop the temp., the rate of sublimation of ice is reduced to require a longer drying time. In order to maintain the rate of sublimation, slight heating is carried out at a fixed time. The resulting dried powder has 0.05-0.003mum small particle size, 120-150m<2>/g large surface area, high activity and favorable sinterability. Conventional powder has 40-70m<2>/g surface area.

Description

[Detailed description of the invention] The present invention relates to a method for producing fine zirconium oxide powder.

In particular, it relates to a method for directly obtaining dried zirconium oxide fine powder.

Conventionally, it has been extremely difficult to directly obtain dried ultrafine powder of zirconium oxide from zirconium hydroxide, and a preferable processing method has been desired. That is, no matter how fine zirconium hydroxide or zirconium oxide is obtained, it takes 200 to
Since heating to 600° C. is required, the particles condense and there is a problem that fine active particles cannot be obtained.

For example, after dissolving E i Z r04 with caustic soda,
Zirconium 71xychloride (ZrOOl) was dissolved in hydrochloric acid.
・8H20) and add NH solution to precipitate zirconium hydroxide. After that, heating and dehydration are performed.

At this time, there was a problem that the above-mentioned 67F shrinkage occurred and a desirable powder could not be obtained.

The present invention solves the following two problems, and relates to a method for producing fine zirconium oxide powder, in which zirconium hydroxide containing water is placed under vacuum, freeze-drying is started, and then heated.

The present invention will be explained in detail below.

Adding an alkaline solution to zirconium oxychloride forms zirconium hydroxide. As the alkaline solution, a solution of NH2, for example, is used. Thereafter, it is dehydrated by filtration or the like, or treated as an aqueous solution.

The next step is drying under vacuum. The vacuum condition is preferably 0. , 5 mHg- or less.

If filtration is performed during pretreatment, place porous porcelain at the bottom of the vacuum chamber and leave it under 7Y air.
Zirconium hydroxide is decomposed into 1(20 and ZrO□,
H2O vaporizes and cooling progresses due to the latent heat of vaporization, freezing occurs, l
Drying is performed. This is one of the two characteristic phenomena of the present invention.

On the other hand, if the freezing progresses too much and the temperature decreases, the speed of sublimation of the ice will be slow and the drying time will be delayed. Accordingly, in the present invention, some heating is performed at certain times.

As mentioned above, some of the excess water evaporates.

Some of the other water is removed through the porous porcelain bottom, and other water freezes into ice and sublimates, removing moisture.

In addition, when processing as an aqueous solution, a method is adopted in which zirconium hydroxide is injected into a vacuum chamber by spraying.

In this case, it is preferable to wait for spraying until freezing starts, and spraying is performed intermittently.

This is because freezing is performed efficiently. Even in this case, if freezing occurs rapidly and sublimation of ice is not efficient, measures are taken to aid sublimation by heating.

In the case of spraying, for example, a cyclone section maintained in a vacuum and a spray section are provided separately, and preferably the spray section is provided on a side wall of the cyclone section.

In addition, when using the spray method, a large amount of water enters the vacuum chamber, so a porous porcelain filter is placed at the bottom of the cyclone section to remove water before and after freezing. It is preferable.

Sunda cyclones t, l: Multiple cyclones may be provided.

If freezing progresses too much, the ice will not sublimate efficiently, so a heating device fR is installed inside or outside the cyclone.

The particle size of the resulting dry powder is O,OSμ~0.003
It is as small as μ, and it is an active powder. Moreover, the surface area was large, 120 to 150 rr?/f, compared to the usual (7) 40 to 7 (l rl/f K).

The powder obtained by this method has good sinterability, and the sintering temperature can be as low as 40 to 70° C. compared to ordinary powder, and a preferable powder can be produced.

By implementing the present invention as described above.

You can obtain the following effects.

■ Complete drying can be performed without the need for cooling means.

■ Zr 02 is immediately ablated from zirconium hydroxide.

■ A fine, non-agglomerated powder is obtained.

(2) There is no spread in the particle size distribution, and a desirable powder can be obtained.

■ Since it is an extremely active powder, it has extremely good sinterability.

(2) Complicated pre-treatments such as ripening, which are found in alkoxide methods and coprecipitation methods, are not required, and ZrO can be easily obtained using ordinary means for producing zirconium hydroxide.

■ Powder with an extremely large surface area can be obtained.

■ The sublimation rate of ice can be increased by heating.

Example 1 Megishi salt and zirconium chloride (ZrOOl.
Ammonia is added to a solution containing 26Of of 8H20) to produce zirconium hydroxide in the form of a sol.

The obtained precipitate is washed with water and dehydrated.

After dehydration, it was placed in a yA empty apparatus and subjected to vacuum treatment. The degree of vacuum at this time is 0.2 wmHf, and the more H and O are vaporized, the more cooling progresses, and the more preferably freeze-drying is performed. However, when freezing progressed excessively, that is, when the temperature reached around -15°C, heating was performed to promote sublimation of the ice. This accelerated the reaction.

Obtained powder iJ: 100 large and 9 surface area 120v
r? /l, which was a preferable powder. Further, the particle size distribution was preferably extremely narrow. Furthermore, since the powder was active, it had extremely good sinterability.

Example 2 Zirconium oxychloride (ZrOOl・8H,
Ammonia was added to a solution containing 26-O) to produce zirconium hydroxide in the form of a sol, and the precipitate was washed with water,
After dehydration, add a small amount of clean water to make a slurry.

When the zirconium hydride that was previously placed under vacuum begins to freeze due to the latent heat of vaporization of H and O, it is discharged from the lower outlet and introduced into a separate vacuum chamber to begin drying again. If freezing progresses excessively (around -15°C), the heating device is activated to quickly sublimate the ice.

Freeze-drying could be performed preferably by performing this sweeping continuously.

The obtained powder was 60'A and had a large surface area of 130 d/l. Moreover, it was a preferable powder because the particle size distribution was extremely narrow. Furthermore, the powder had extremely good sinterability due to its activity.

Patent applicant: Nippon Kodo Co., Ltd. Agent: Patent attorney (7569) Keishi Namikawa

Claims (1)

[Claims] (1) A method for producing fine zirconium oxide powder, which comprises dispersing zirconium hydroxide containing water in a vacuum, starting freeze-drying, and then heating it.