JPH0529626B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to zirconia, which has many applications not only in functional ceramics such as solid electrolyte sensors, but also in structural ceramics such as heat insulating materials and fireproof materials. It is related to the production of molded products, and in particular, it is produced by hydrolyzing zirconium alkoxide with crystallization water of one or more salts selected from zirconia stabilizers such as yttrium, calcium, magnesium, cerium, etc. The present invention relates to stabilization or partial stabilization and a method for producing a tetragonal zirconia molded product.

[Conventional technology]

In recent years, synthetic methods using hydrolysis of metal alkoxides have been actively researched as a method for obtaining high-quality ceramics. The so-called sol-gel method using a metal alkoxide yields a product of higher purity than the commonly used method of mixing metal oxide fine powder and calcining the mixture.

2. Highly homogeneous products can be obtained.

3. Low-temperature manufacturing process is possible.

4. There is freedom in giving shapes.

There are high expectations for the development of highly functional ceramics due to their many advantages.

With this method, particles, fibers, glass lumps,
Ceramic products in the form of films or the like can be obtained.

In the method for producing zirconia using zirconium alkoxide, zirconium alkoxide is dissolved in an organic solvent such as benzene, ethanol, isopropanol, etc., and the amount of water for hydrolysis, pH,
Bulk gels, fibers, and coatings are produced by strictly controlling the hydrolysis rate and polycondensation reaction by varying the aging temperature and time.

For example, Saito et al. (Journal of the Chemical Society of Japan 1988, No.
9, P1571-1577), the hydrolysis of zirconium alkoxide was controlled by changing the amount of hydrolysis, pH, aging temperature, and time, and the reaction rate was adjusted to PH = 2.
It has been reported that in the system with PH = 10, lumps are obtained.

In addition, Yokoo et al.
Vol.9, P163-175 (1988)) is Zr ₍ 0- _nC3H7 ) ₄
Acid is added to the solution, mixed with stirring, aged at 80°C, and the resulting viscous solution is spun to obtain gel fibers.

[Problem to be solved by the invention]

However, with these methods, the operations are complicated, most of the work must be done in a glove box to prevent air contact, and white precipitation may occur if the water is slowly soaked. It is necessary to add it so that it is not present. It is difficult to industrialize because the operation is complicated.

The object of the present invention is to solve the above-mentioned drawbacks, to provide an ultra-high purity, stabilized or partially stabilized, tetragonal zirconium molded product that is easy to manufacture and of high quality.

[Means to solve the problem]

The present invention involves adding a metal salt having water of crystallization to a solution of zirconium alkoxide, hydrolyzing it with the water of crystallization to produce a sol, forming a gel-like molded product from the sol, and producing a gel-like molded product from the sol. This is a method for producing a stabilized or partially stabilized and tetragonal zirconia molded product characterized by firing, and thereby the above-mentioned problems can be solved.

Further, in the present invention, the metal salt having water of crystallization may be yttrium, calcium, magnesium,
Alternatively, it is preferable that at least one type is selected from the group consisting of cerium chloride, nitrate, sulfate, carbonate, oxalate, or acetate.

In the present invention, the gel-like molded product formed from a sol and the molded product of the fired molded product refer to those having the shape of particles, fibers, lumps, membranes, sheets, etc., and are pressure-molded by press processing etc. It is not limited to products. That is, the shape is not particularly limited and includes any shape.

Examples of the zirconium alkoxide used in the present invention include zirconium methoxide, zirconium ethoxide, zirconium isopropoxide, zirconium normal propoxide, and zirconium normal butoxide. Among these alkoxides, there are those that are solid and those that are liquid at room temperature, and both are used as a solution by dissolving them in an organic solvent. As the organic solvent for dissolving the zirconium alkoxide, alcohols such as methyl alcohol and ethyl alcohol, benzene, toluene, xylene, etc., or mixtures thereof can be used.

Zirconium alkoxide is rapidly hydrolyzed and easily forms a white precipitate when water is added. Therefore, in the present invention, one or more salts selected from yttrium, calcium, magnesium, cerium, etc., which function as a stabilizer for zirconia, are slowly hydrolyzed with crystallization water. Monolithic gel can be produced by operation in air.

Also, the crystal water salt used in accordance with the present invention must be soluble in the organic solvent used to dissolve the zirconium alkoxide. The above salts include YCl ₃・6H ₂ O, Y ₂ (SO ₄ ) ₃・8H ₂ O, Y
(NO ₃ ) ₃・6H ₂ O, Y ₂ (CO ₃ ) ₃・3H ₂ O, Y (CH ₃
COO) ₃・4H ₂ O, Y ₂ (C ₂ O ₄ ) ₃・9H ₂ O, CaCl ₂・
H ₂ O, Ca (ClO) ₂・3H ₂ O, CaSO ₄・2H ₂ O, Ca
(NO ₃ ) ₂・4H ₂ O, Ca (C ₂ O ₄ )・H ₂ O, Ca (CH ₃
COO) ₂・H ₂ O, MgCL ₂・6H ₂ O, Mg(ClO ₄ )・
6H ₂ O, MgSO ₄・H ₂ O, MgSO ₄・7H ₂ O, Mg
(NO ₃ ) ₂・6H ₂ O, Mg (CH ₃ COO) ₂・4H ₂ O, Mg
(C ₂ O ₄ )・2H ₂ O, Ce (ClO ₄ ) ₃・6H ₂ O, Ce (OH)
₄・H ₂ O, Ce (SO ₄ ) ₃・8H ₂ O, Ce (NO ₃ ) ₃・8H ₂
O, etc., and one or more types can be appropriately selected and used from these.

The gel-like molded product is produced by adding an appropriate amount of one or more of the above salts to a solution of zirconium alkoxide, sealing the container and stirring, and after the salt has completely dissolved, hydrolysis is performed. It is synthesized by aging a sol at room temperature or an appropriate temperature.

It is desirable to adjust the amount of the salt having crystallization water so that the amount of H ₂ O in the crystallization water is 4 times or less, preferably 0.01 to 1 mole, per mole of zirconium alkoxide.

In addition, the aging process is performed by keeping the sol at a temperature of 20°C to 80°C.
It is carried out by leaving it under normal pressure = 1 atm for 1 to 180 days.

The resulting gel-like molded product is fired at a suitable temperature of 400°C to 1800°C to produce a stabilized or partially stabilized and tetragonal zirconia molded product. The stabilization or partial stabilization of the zirconia molded product means the state of cubic zirconia in the former case, and the state in which tetragonal zirconia is dispersed in cubic zirconia in the latter case.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

(Example 1) 200 ml of 0.1 mol of zirconium isopropoxide
was dissolved in ethanol. dissolved in solution
Add 0.01 mol of YCl ₃ 6H ₂ O, close the cap tightly and stir.
After completely dissolving, it was transferred to a polypropylene container and sealed. A gel-like material was formed by placing it in a dryer at 80°C for one month, and then firing it at 1350°C for 2 hours to create a tetragonal zirconia bulk body.

(Example 2) Add 5.9 g of MgCl ₂ 6H ₂ O to 111 g of zirconium butoxide butanol solution (90 wt% solution) and dissolve completely, then transfer to a polypropylene container, seal it, and put it in a dryer at 80 ° C. After 1 week When the gel was taken out and fired at 1700°C for 2 hours, a tetragonal zirconia bulk body was created.

(Example 3) Zirconium butoxide butanol solution (90wt% solution) was separated so that zirconium butoxide was 0.1 mole, 0.01 mole of YCl ₃ 6H ₂ O was added and dissolved, and then transferred to a polyethylene container and sealed. did. One day later, it had become a viscous sol. They spun it by dipping a Teflon rod into it.
When the fiber was fired at 1200°C for 2 hours, a cubic stabilized zirconia fiber was created.

(Example 4) 200 ml of 0.1 mol of zirconium isopropoxide
was dissolved in ethanol. dissolved in solution
0.022 mol of YCl ₃ .6H ₂ O was added, the mixture was tightly capped and stirred to completely dissolve, and then transferred to a polypropylene container and sealed. Place it in a dryer at 80°C for one month to form a gel-like material, then bake it at 1700°C for 2 hours, then anneal it at 1300°C for 2 hours to create a partially stabilized zirconia bulk body. did.

〔Effect of the invention〕

In the present invention, since the hydrolysis of zirconium alkoxide is carried out using salt crystallization water, it is possible to stably provide gel molded products and ceramics thereof that are easy to operate and of good quality. Furthermore, since the crystal water is used, hydrolysis progresses gradually and uniformly to form a sol, so for example, by putting the sol in a container of a desired shape and aging it, an integrated gel molded product and Since ceramics can be obtained extremely easily, they can be used in a variety of shapes and contribute greatly to improvements in labor saving and economic efficiency.

Claims (1)

[Claims] 1. Adding a metal salt having water of crystallization to a solution of zirconium alkoxide, hydrolyzing with the water of crystallization to produce a sol, forming a gel-like molded product from the sol, A method for producing a stabilized or partially stabilized and tetragonal zirconia molded product, which comprises firing the molded product. 2 The metal salt having water of crystallization is ythtrium,
The stabilizer or moiety according to claim 1, characterized in that the stabilizer or moiety is selected from the group consisting of chloride, nitrate, sulfate, carbonate, oxalate, or acetate of calcium, magnesium, or cerium. A method for stabilizing and producing a tetragonal zirconia molded article.