JPH03112862A - Preparation of raw material fine powder for zirconia ceramic and zirconia ceramic - Google Patents

Abstract

PURPOSE:To provide raw material fine powder having improved slurry formability and moldability without containing strong coagulated secondary particles by sintering a zirconia ceramic material and subsequently finely impact- grinding the calcined product. CONSTITUTION:A kind or more of zirconia ceramic materials synthesized by a known wet process or dry process and containing a stabilizer is calcined at 600-1300 deg.C in the atmosphere for 1-24hrs. The calcination product is, if necessary, crushed up to the maximum particle size of 2mm, fed into a high speed rotation type impact grinding machine, impact-ground at a rotation number of 10000-20000rpm and subsequently classified into raw material fine powder having an average volume particle size of 0.8-10mum and a bulk density of 0.3-0.7 and used for preparing zirconia ceramic. The raw material and a dispersing agent are dispersed in water to form a slurry, which is molded and sintered to provide a zirconia ceramic sintered product having a flexual strength of >=1100MPa.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a raw material fine powder for producing zirconia ceramics, and to zirconia ceramics obtained using this fine powder.

Conventional technology and its problems Conventionally, fine powder raw materials for manufacturing zirconia ceramics are produced by synthesizing zirconia material through a wet process or a dry process, and then
It is manufactured by calcining, or by preparing and mixing raw material powders, calcining, and pulverizing the calcined product. The pulverization process carried out at this time is roughly divided into a wet pulverization method and a dry pulverization method.

The wet pulverization method has the advantage that the material to be pulverized can be pulverized well, but since water, an organic solvent, etc. are used as a dispersion medium, a drying step is required after pulverization. For drying the pulverized material, methods such as granulation drying using a spray dryer, direct drying, etc. are used.

The granulation drying method has a major problem in that the equipment cost is high. Furthermore, when water is used as a dispersion medium in the direct drying method, particularly strong agglomeration of powder occurs during evaporation and drying of the water. When using zirconia ceramic raw material powder containing a large amount of strongly agglomerated secondary particles in this way, for example, when performing casting molding, the dispersibility of the powder in the slurry will be poor, so dispersants etc. Not only does this require the use of a large amount of additives, but the workability is also reduced, and it is difficult to obtain a homogeneous sintered body. On the other hand, when an organic solvent is used as a dispersion medium, the problem of powder aggregation is alleviated, but sufficient consideration must be given to disaster prevention and handling, such as making the drying equipment explosion-proof. Therefore, in addition to the cost of the organic solvent, the cost of the drying equipment also increases, which is economically disadvantageous.

Equipment such as dry ball mills, roller mills, and jet mills are used in the dry grinding method.

In the dry ball milling method, pulverization is performed mainly by the friction of the pulverizing media, so the material to be pulverized is strongly compressed by the pulverizing media, and as a result, a powder containing many solid (agglomerated) secondary particles is formed. In addition, due to the over-grinding phenomenon, some ultra-fine powder is generated, which promotes the agglomeration of the powder. Grinding with a roller mill produces almost the same powder as that with a dry ball mill, so it is still homogeneous. It is difficult to obtain a sintered body.In the case of pulverization using a jet mill, since the pulverization mechanism is based on collision of the objects to be crushed, agglomeration of the pulverized materials does not occur.

However, this pulverization method is not suitable for pulverizing a large amount of raw materials, and the ratio of equipment cost to pulverization processing capacity becomes large, which is economically disadvantageous.

Means for Solving the Problems The inventor of the present invention has carried out intensive research in view of the problems of the prior art as described above, and as a result, after calcining a zirconia material synthesized by a conventional dry process or wet process, It has been found that when impact pulverized, a fine powder for producing zirconia ceramics can be obtained which does not substantially contain strong agglomerated secondary particles, is easy to mold, and forms a uniform sintered body.

That is, the present invention provides the following method for producing raw material fine powder for producing zirconia ceramics and a zirconia ceramic sintered body obtained using the powder: [3] Synthesized in a wet process and a dry process. After calcining one or a mixture of two or more of the zirconia ceramic materials, the calcined material is impact pulverized to a volume average particle diameter of 0.8 to
A method for producing fine raw material powder for producing zirconia ceramics, characterized by obtaining powder of 10 μm.

(2) A zirconia ceramic sintered body having a bending strength of 1100 MPa or more obtained by molding and sintering the zirconia ceramic raw material fine powder produced by the method described in the above item (2).

[3] After calcining one or a mixture of two or more zirconia ceramic materials synthesized in a wet process and a dry process, the calcined material is crushed to a maximum particle size of 21111 or less, and then impact pulverized to obtain a volume average A method for producing fine powder of zirconia ceramic raw material, characterized by obtaining powder having a particle size of 0.8 to 10 μm.

(2) A zirconia ceramic sintered body having a bending strength of 1100 MPa or more obtained by molding and sintering the zirconia ceramic raw material fine powder produced by the method described in the above item (2).

The zirconia material used as a starting material in the present invention may be manufactured by a known wet process or dry process, or may be a mixture of two or more types obtained by different manufacturing methods. Such zirconia materials typically contain known stabilizers such as yttria, magnesia, calcia, rare earth oxides, and the like. In addition, the particle size of the zirconia material is not particularly limited, but is usually 0.1 to 100 μm.
It is preferable that it is about m.

In the present invention, the powdered zirconia material as described above is calcined. Calcination is performed by heating the zirconia material in an air atmosphere.
This is carried out by heating at about 00 to 1300°C for about 1 to 24 hours.

Next, the calcined zirconia powder obtained above is pulverized by impact. The dimensions of the calcined material to be subjected to the pulverization treatment are preferably such that the maximum particle size is 2 mm or less, and more preferably 1 mm or less. Therefore, if necessary, the calcined material may be crushed in advance prior to pulverization.

Impact milling can be carried out, for example, by various types of impact mills. Examples include high-speed rotary impact mills. This is a type of pulverizer that rotates two opposing disks with a large number of bottles arranged at high speed, supplies the calcined material between them to be pulverized, and pulverizes the material by impact between the pins. be. The high-speed rotating impact crusher may be of the type (a) in which two disks rotate in opposite directions, or (b) the type in which one disk is fixed and the other rotates. It could be something like that. The number of rotations of the disks is appropriately determined depending on the crushability of the calcined material, the required particle size of the fine powder, etc., but for type (a), the total number of rotations of the two disks is 10,000 to 2,000 Orp.
m, type (b), rotation speed 10,000~
It is about 2000 rpm.

The particle size of the zirconia fine powder obtained by the above-mentioned pulverization is required to be in the range of 0.8 to 10 μm as an average volume particle size. When the particle size of the fine powder is more than 10 μm or less than 0.8 μm, the finely pulverized product may be classified to adjust the particle size.

The zirconia fine powder obtained by such a pulverization operation does not contain hard agglomerated particles and is a bulky powder, and its bulk density is about 0.3 to 0.7.

This fine powder also has good dispersibility and moldability, for example,
The amount of dispersant (for example, polyacrylic acid type, etc.) required to prepare a slurry for casting molding having a concentration of about 75% by weight and a viscosity of about 100 cps is only about 0.25% by weight. The amount of this dispersant used is about 1/4 of the amount required to slurry a pulverized product using a known dry ball mill.

Further, when the fine zirconia powder according to the present invention is formed into beads by the transfer granulation method, beads having a diameter of approximately 1 to 10 mm+, which is extremely close to a true sphere, can be obtained. This is because the fine powder does not contain coarse secondary particles that are tightly aggregated, so the compaction during molding becomes better. On the other hand, for example, with fine powder obtained by a known wet ball mill, it is not possible to mold beads that are close to perfect spheres. This is because in this case, since there are many secondary particles that are tightly aggregated, the molding pressure is not applied uniformly during granulation, resulting in beads having an irregular shape.

The raw material fine powder for producing zirconia ceramics produced by the method of the present invention is molded and fired by a conventional method to produce a zirconia ceramic product.

This product is superior to products manufactured from fine raw material powder for producing zirconia ceramics by conventional methods in terms of bending strength, bulk density, formability, etc. of the molded body.

Effects of the Invention The raw material fine powder for producing zirconia ceramics produced by the method of the present invention has extremely few agglomerated particles, so it is easy to form a slurry, and the number of uses for the dispersant is greatly reduced, thus reducing the production cost of ceramics. Reduced.

Furthermore, the equipment used to crush the zirconia material is also downsized, so equipment costs are also reduced.

Furthermore, various physical properties of zirconia ceramics produced using the fine powder obtained as described above are also improved. For example, the bending strength usually reaches 1100 MPa or more.

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention.

Example 1 A zirconia material (Ittria content M-i = 3 mol%) produced by a hydrolysis method was calcined at 850°C for 10 hours, and the resulting calcined product was crushed to a maximum particle size of 1 mm or less. A crude raw material powder was obtained.

Next, a high-speed rotary impact crusher of the type in which one of two discs rotates (diameter of disc = 160 mm, number of pins = 40
0) was operated at a rotational speed of 1800 rpm, the above crude raw material powder was supplied at a rate of 10 kg/hour and subjected to impact pulverization.

The volume average particle size of the zirconia fine powder thus obtained is:
The bulk density was approximately 1.5 μm and 0.60.

Using this zirconia fine powder and blending 0.25% of a polyacrylic acid dispersant, an aqueous slurry with a solid content concentration of 73% by weight was prepared, and by a conventional casting method, 6
Molded into a size of 0nm x 80mm x 6mm, 1500
It was baked at ℃ for 3 hours to obtain a test piece.

The relative density of the obtained test piece was 99.5%, and JI
The three-point bending test strength according to S R1601 is approximately 12
It showed a value of 00 MPa.

Table 1 shows the results of this example as well as the results of similar test pieces obtained using pulverized products produced by the known dry ball mill method.

Table 1 Example 2 A zirconia material (yttria content = 3 mol%) produced by a hydrolysis method was calcined at 1050°C for 10 hours, and the resulting calcined product was crushed to a maximum particle size of 1 mm or less. A crude raw material powder was obtained.

Next, a high-speed rotary impact crusher of the type in which one of two discs rotates (diameter of disc = 160a + m, number of pins = 4)
00) was operated at a rotational speed of 18,000 rpm, the above crude raw material powder was supplied at a rate of 10 kg/hour and subjected to impact pulverization.

The zirconia fine powder thus obtained was classified and coarse particles were removed, and the volume average particle size of the fine powder was approximately 1.6 μm.
The bulk density was 0.52.

Using this zirconia fine powder, beads with a diameter of 2 mm were molded by a transfer granulation method and fired at 1500° C. for 3 hours.

Table 2 shows the physical properties of the sintered body obtained in this example.

Table 2 also shows the characteristics of a sintered body using powder obtained by a known wet ball milling method using ethanol as a solvent.

Claims (1)

[Claims] [1] After calcining one or a mixture of two or more zirconia ceramic materials synthesized in a wet process and a dry process, the calcined material is impact-pulverized to have a volume average particle diameter of 0. 8～
A method for producing fine raw material powder for producing zirconia ceramics, characterized by obtaining powder of 10 μm. [2] A zirconia ceramic sintered body having a bending strength of 1100 MPa or more obtained by molding and sintering the zirconia ceramic raw material fine powder produced by the method according to claim [1]. [3] After calcining one or a mixture of two or more zirconia ceramic materials synthesized in a wet process and a dry process, the calcined product is crushed to a maximum particle size of 2 mm or less, and then impact pulverized to obtain a volume average A method for producing fine raw material powder for producing zirconia ceramics, characterized in that powder having a particle size of 0.8 to 10 μm is obtained. [4] A zirconia ceramic sintered body having a bending strength of 1100 MPa or more obtained by molding and sintering the zirconia ceramic raw material fine powder produced by the method according to claim [3].