JPH01301520A - Production of alumina-zirconia multiple powder - Google Patents

Abstract

PURPOSE:To obtain the title multiple powder with the constituent homogeneously mutually mixed at a microscopic level, by mixing an aqueous solution of zirconate and an organic solvent solution of aluminum alkoxide with each other followed by hydrolysis with ammonia and then calcining the multiple precipitate produced. CONSTITUTION:An aluminum alkoxide [e.g. Al(i-C3H7O)3] organic solvent solution or boehmite-dispersed water-organic solvent solution is mixed with an aqueous solution of zirconate [and, if needed, spiked with water-soluble salt(s) of Y, Mg, Ca, Ce, etc. as a stabilizer]. The resultant mixture is then spiked with ammonia or ammonium carbonate to effect hydrolysis and the resulting homogeneous mixture comprising alumina hydrate and zirconia hydrate is filtered and dried and then calcined at 800-1,300 deg.C, pref. at 900-1,100 deg.C, thereby obtaining the objective multiple powder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing alumina-zirconia composite powder, which is a raw material for ceramic materials having high toughness, high strength, high hardness, and excellent wear resistance.

BACKGROUND OF THE INVENTION In recent years, alumina-zirconia composite ceramics have come to be used in a variety of applications as materials with high toughness, high strength, and high hardness.

In the production of alumina-zirconia composite ceramics, alumina and zirconia can be mixed using method 1 of mechanically mixing raw material alumina powder and zirconia powder using a ball mill or the like, or a method of obtaining alumina-zirconia composite powder from a liquid phase. . The latter method involves neutralizing an aqueous solution containing aluminum salts and zirconium salts and calcining the resulting mixed hydrate of alumina and zirconia, or by hydrolyzing a mixed organic solvent solution of aluminum and zirconium alkoxides. There is a method of calcining a mixed hydrate of alumina and zirconia.

Problems to be Solved by the Invention In alumina-zirconia composite ceramics, it is important to have dispersed particles uniformly and finely present in the matrix in order to produce ceramics with desired characteristics. For this purpose, it is necessary that the raw material powders be mixed uniformly at a microscopic level, and that the powder be sufficiently fine and have excellent sinterability.

Conventional mechanical mixing using ball mills, etc., makes it difficult to mix alumina powder and zirconia powder uniformly down to a sufficiently microscopic level. Ceramics are difficult to obtain.

In addition, the method of producing an alumina-zirconia composite powder by obtaining precipitates or hydrates mixed in a liquid phase and calcining them is superior in terms of uniform mixing at a micro level.

However, in the method using an aqueous solution of an aluminum salt and a zirconium salt, the resulting alumina-zirconia composite powder has a strong cohesive force, and it is difficult to obtain a sufficiently fine powder by pulverization.

When alkoxide is used, there is a problem that zirconium alkoxide is expensive and difficult to put into practical use.

In view of this situation, an object of the present invention is to provide an inexpensive method for producing alumina-zirconia composite powder, which is sufficiently uniformly mixed at a microscopic level, has a weak cohesive force, and has high sinterability.

Means for Solving the Problems The method of the present invention involves mixing an aqueous solution in which a zirconium salt is dissolved and a six-unit solvent solution in which an aluminum alkoxide is dissolved, and adding ammonia or ammonium carbonate to this mixed solution to obtain alumina water. A method for producing alumina-zirconia composite powder, which is characterized by calcining a composite precipitate of zirconium hydrate and zirconia hydrate, and further adds yttrium salt and magnesium salt as a stabilizer to an aqueous solution in which the zirconium salt is dissolved. It is also possible to add at least one water-soluble salt among calcium salts, cerium salts, ittria, magnesia, calcia, and ceria.

Moreover, instead of the above-mentioned organic solvent solution in which aluminum alkoxide is dissolved, a water/organic solvent solution in which boehmite is dispersed can also be used.

The boehmite mentioned here has 1.0 to 2.0 moles of crystal water per 2031 moles of Al, and in X-ray diffraction, the h-spacing of the (020) plane is 6.1 to 6.8. refer to something.

The present invention will be described in further detail below.

First, the case where aluminum alkoxide is used as the alumina source will be explained.

First, an aqueous solution in which a zirconium salt is dissolved is prepared. The zirconium salt used here is zirconium acid chloride,
Any material such as zirconium nitrate that is water-soluble and can form a hydrate by adjusting the pH may be used.

Next, an organic solvent solution in which aluminum alkoxide is dissolved is prepared. The aluminum alkoxide used here may be one such as aluminum isopropoxide, aluminum butoxide, etc., as long as it dissolves in an organic solvent and produces a hydrate by hydrolysis.

Isopropyl alcohol, butyl alcohol, ethyl alcohol, benzene, etc. can be used as the organic solvent.

Next, an aqueous solution of zirconium salt is added to the organic solvent solution of aluminum alkoxide to cause hydrolysis of the aluminum alkoxide. Ammonia water or ammonium carbonate aqueous solution is added to this mixed solution to neutralize the zirconium salt. Caustic soda, caustic potash, and the like are not preferred because they cause Na and K to be mixed into the precipitated product.

The amount of ammonia water, etc. is greater than the amount necessary to neutralize the zirconium salt. The temperature of the organic solvent solution of aluminum alkoxide and the aqueous solution of zirconium salt is not particularly limited, but it is preferable to use them heated, since the solubility of aluminum alkoxy L' used therein is better.

The mixed solution thus obtained becomes a uniform mixed solution containing precipitates of alumina hydrate and zirconia hydrate.

It is necessary to avoid adding aqueous ammonia or the like in advance to an aqueous solution in which a zirconium salt is dissolved.

Even if an organic solvent solution of aluminum alkoxide is then added thereto, it is not possible to obtain a composite powder having a weak cohesive force and having a uniform composition at the microscopic level, which is the object of the present invention.

By adjusting the zirconium salt and aluminum alkoxide used, an alumina-zirconia composite powder having the desired ratio can be obtained.

If necessary, at least one of yttrium salts, magnesium salts, calcium salts, cerium salts, yttrium, magnesia, calcia, and ceria may be added as a stabilizer by preliminarily adding the desired amount to the aqueous solution of the zirconium salt. It can be nailed.

The obtained homogeneous mixed solution is dried or filtered, and after drying, it is calcined at 800-1300°C, preferably 900-1100°C.

After calcining, the powder is pulverized by a conventional method.
The desired fine-grained alumina-zirconia composite powder is obtained.

Further, as an alumina source, instead of an organic solvent solution in which aluminum alkoxide is dissolved, a water/organic solvent mixed solution in which boehmite is dispersed can also be used. Any boehmite may be used as long as it can be dispersed in a mixed solution of water and an organic solvent and turned into a sol. The organic solvent is isopropyl alcohol,
Ethyl alcohol, benzene, etc. can be used.

The ratio of water to organic solvent is preferably 1 part water to 1 part or more of the organic solvent.

The basic operation is basically the same as that for the aluminum alkoxide 6 solvent solution described above.

Function The present invention is characterized in that the neutralization of the zirconium salt is carried out in a liquid containing an organic solvent, and the organic solvent is an organic solvent solution of aluminum alkoxide, which is a derivative of alumina, or a dispersion of boehmite. water a
By utilizing the organic solvent in the organic solvent mixture solution, there is no need to use other additives.

Furthermore, by reacting and mixing in the liquid phase, the constituent components are mixed uniformly at a microscopic level.

Even if the homogeneous mixed solution of alumina hydrate and zirconia hydrate produced under these conditions was filtered and the mixed hydrate was dried by simple static drying, the dried powder would not solidify into a block shape. The powder has an average diameter of 1 to 4 um when determined by a laser diffraction granulometer to 7111.

In order to weaken the cohesive force of the mixed hydrate after drying, the procedure is very important in producing the hydrate as described above.

Even after calcination, the powder maintains its weak cohesive strength,
Fine-grained alumina-zirconia composite powder can be obtained.

Example (1) Zirconium acid chloride (ZrO(1) ・8H20) 1
29 g and yttrium chloride (Y CII 6H2
0) An aqueous solution was prepared by dissolving 7.3 g in 500 ml of water and maintained at 80°C.

Next, aluminum isopropoxide [AfI(i-C3
H70) 3) 49g isopropyl alcohol 101
A solution was prepared by dissolving 00O and maintained at 80°C.

A solution containing zirconium acid chloride was added to a solution containing aluminum isopropoxide and thoroughly stirred to form a mixed solution.

Aqueous ammonia was added to the mixed solution until the pH reached 7.0, and the mixture was thoroughly stirred.

This mixed solution was filtered and left to dry in a hot air dryer.

The particle size of the obtained mixed hydrate was determined using a laser diffraction type granulometer with a>1, and the average diameter was 2.8p.

Further, it was calcined at 1100°C for 2 hours, and the alumina-zirconia composite powder (20wt% alumina, 80vt% zirconia (3*oN% ittria a white degree)) was heated to 84Kk'.
J.

From the X-ray diffraction results of this powder, peaks of δ-alumina, θ-alumina, tetragonal zirconia, and a slight monoclinic zirconia were observed.

The square content was 94%.

Also, the average diameter of this powder was determined to be 4.0-BE by the same method as described above.
T specific surface area is 14.5rr? /g.

Furthermore, after crushing this powder with a ball mill, 2000
kg/cj and sintered at 1500°C for 2 hours under normal pressure. The sintered bulk density was 5.5 g/c [11].

Example (2) A mixed hydrate obtained in the same manner as in Example (1) was mixed with 11
It was calcined at 80°C for 2 hours.

From the results of X-ray diffraction of this powder, peaks of θ-alumina, α-alumina, tetragonal zirconia, and slightly fit orthorhic zirconia were observed. IEh crystal content is 91%
Met.

Also, the average diameter of this powder was determined to be 2.9 and BE by the same method as described above.
T specific surface area is 8.0rr? /g.

Example (3) Zirconium acid chloride (ZrOC, 77.8H20) 12
9g and 12.7g of Ittria (Y2O2) in 500m of water
A solution of water/8 dissolved in 1 was prepared and maintained at 80°C.

Next, add 27g of boehmite to 10U of isopropyl alcohol.
Oml, dispersed in a mixture of 500ml of water, 1 sip:)tl
, adjusted to pH 3.0 with HCN and kept at 80°C.

A solution containing zirconium acid chloride was added to a solution containing boehmite and thoroughly stirred to obtain a mixed solution.

Aqueous ammonia was added to the mixed solution until the pH reached 7.0, and the mixture was thoroughly stirred.

This mixed solution was dried in a retired air dryer after passing if5.

The average particle size of the obtained mixed hydrate was determined by the same method as described above.
．． The time was 6 μs.

Further, it was calcined at 1100℃ for 2 hours to obtain alumina-zirconia powder (20vL% alumina, 80vL% zirconia (
3■o (1% ittria@H)) was obtained in 63 ml.

X-ray diffraction revealed peaks of δ-alumina, θ-alumina, tetragonal zirconia, and slight monoclinic zirconia in this powder.

The square content of zirconia was 9496. In addition, the average particle size of this powder was determined to be 4.2 mm by the same method as described above, and the BE
The T specific surface area was 13.97g.

Furthermore, after crushing this powder with a ball mill, it becomes 2000kg/c.
When the molded material was molded at J and sintered under normal pressure for 1500'02 hours, the sintered bulk density was 5.48 g/cIfl.

Comparative Example (1) The same amount of zirconium acid chloride aqueous solution (containing yttrium chloride) and isopropyl alcohol solution of aluminum isopropoxide as in Example (1) were mixed with Jl! 1 adjustment and both liquids are 8
It was kept at 0°C.

First, add ammonia water to the zirconium acid chloride solution to pH
of 7.0 to cause hydrate precipitation of zirconium and yttrium.

'Next, this solution for precipitating zirconium and yttrium hydrates was added to an isopropyl alcohol solution of aluminum isopropoxide and thoroughly stirred to form alumina hydrates.

This mixed solution was filtered and left to dry in a retired hot air dryer. The mixed hydrate after drying was a flake-like mass with strong cohesive force, and it was difficult to pulverize it by normal pulverization.

Comparative Example (2) The same amount of zirconium acid chloride aqueous solution (containing yttrium oxide) as in Example 3 and 27 g of boehmite were added to 500 ml of water.
A solution was prepared which was dispersed in 1096 HC and adjusted to pl+3.0 with 17, and both solutions were maintained at 80°C.

First, add ammonia water to the zirconium acid chloride solution to pH
7.0 to precipitate hydrates of zirconia and ittria.

Next, the liquid containing the zirconia and yttria hydrate precipitates was added to the aqueous solution in which boehmite was dispersed and thoroughly stirred.

This mixed solution was quenched and left to dry in a hot air dryer. The mixed hydrate after drying was a flake-like mass with strong cohesive force, and it was difficult to pulverize it by normal pulverization.

Effects The method according to the present invention provides an inexpensive method for producing alumina-e-zirconia composite metal powder that has weak cohesive force and is uniformly mixed at a microscopic level.

Claims (3)

[Claims] 1. An aqueous solution in which a zirconium salt is dissolved and an organic solvent solution in which an aluminum alkoxide is dissolved are mixed, ammonia or ammonium carbonate is added to this mixture, and the resulting composite precipitate of alumina hydrate and zirconia hydrate is calcined. A method for producing an alumina-zirconia composite powder, characterized by: 2. Mix an aqueous solution in which a zirconium salt is dissolved and a water/organic solvent solution in which boehmite is dispersed, add ammonia or ammonium carbonate to this mixture, and precipitate the resulting composite precipitate of alumina hydrate and zirconia hydrate. A method for producing alumina-zirconia composite powder, which is characterized by firing. 3. Yttrium salt, magnesium salt, calcium salt,
3. The method according to claim 1, further comprising at least one of cerium salt, yttria, magnesia, calcia, and ceria.