JP3284244B2 - Zirconium oxide powder and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to zirconium oxide powder. Zirconium oxide powder is usually mixed with other powders, molded, and sintered to produce various materials. For example, solid electrolytes, piezoelectrics, wear-resistant materials,
It is used in large quantities in the manufacture of abrasives and the like. Further, a material obtained by adding a stabilizer such as yttria, magnesia, and calcia to this is used for producing a structural material or the like made of a stabilized or partially stabilized zirconia sintered body.

[0002] In the present specification, the term "primary particle size" refers to a particle having a particle size of about 1 to 1000 nm which can be measured by a transmission electron microscope or a particle size distribution measuring device by a photon correlation method. Refers to the particle size of the volume-based distribution measured by a particle size distribution measuring device or the like, and “average particle size” refers to a so-called median size, and the cumulative distribution of the particle size is 50%.
%. In this specification, the term “hydrated zirconia” refers to what is called zirconium hydroxide, crystalline hydrated zirconia, amorphous hydrated zirconia, or the like.

[0003]

2. Description of the Related Art Conventionally, a material obtained by adding a stabilizer such as yttria, magnesia, and calcia to a powder of zirconium oxide, forming and sintering the resulting material to form a stabilized or partially stabilized zirconia sintered body. Are manufactured. As the molding method, a press molding method in which powder is put into a mold and pressurized with a piston or the like, or a slurry casting method in which slurry is poured into a casting mold and solidified is used.

[0004]

However, conventional powders still have problems. That is, moldability such as occurrence of defects such as lamination (composing a layered structure) when performing press molding, slow deposition speed when performing slurry casting, and clogging of a gypsum casting mold. Is a problem. When such a problem occurs, the density and strength of the product and the productivity are reduced. This poor formability is particularly problematic when large products are manufactured or when a large number of products are industrially manufactured by automatic pressing. An object of the present invention is to provide a zirconium oxide powder which has improved the above-mentioned problems, has good moldability, and can produce a high-density, high-strength sintered body.

[0005]

The present inventors have conducted intensive studies and found that the BET specific surface area is 1 to 10 m ² / g, the average particle size is 0.1 to 1 μm, and the cumulative distribution is 0.1 μm.
And zirconium oxide powder characterized in that the proportion of particles having a particle size exceeding 10 μm is 5% or less can achieve the above-mentioned object. Hereinafter, the inventors have found that a suspension of hydrated zirconia particles having a primary particle diameter of 50 to 150 nm is dried and then calcined, thereby completing the invention.

The details will be described below. The zirconium oxide powder of the present invention has a BET specific surface area of 1 to 10 m ^2.
/ G, and an average particle diameter of 0.1 to 1 μm. When the BET specific surface area is larger or the average particle size is smaller than the above range, for example, it is difficult to use a high-concentration slurry due to an increase in the viscosity of the slurry when performing slurry casting, or a gypsum mold. When it is placed in a fine powder, the inlay speed is slow to block the gypsum pores, and furthermore, when performing press molding, the transmission of the molding pressure is poor because the particles are too small, or lamination occurs. In any case, it is difficult to obtain a high-density product. On the other hand, when the BET specific surface area is smaller than this range or the average particle size is larger, that is, when the zirconium oxide powder particles are large and coarse, it is difficult to obtain a sintered body with high density and high strength. BET from the range
When only the specific surface area is large or only the average particle diameter is large, the zirconium oxide powder is agglomerated firmly of fine particles, and pores between the fine particles are likely to remain as they are even after molding and sintering. It is difficult to obtain a sintered body having a high density.

Further, the zirconium oxide powder of the present invention comprises:
It is essential that the proportion of particles having a cumulative distribution of 0.1 μm or less and exceeding 10 μm is 5% or less. Regarding the condition of the cumulative distribution, the ratio of particles having a particle size of 0.1 μm or less and 10 μm or more is preferably 1% or less, and the ratio of particles having a particle size of 0.1 μm or less and 5 μm or more is more preferably 1% or less.

If the cumulative distribution is out of the range of the conditions, there are too many fine or coarse particles in the particles, so that good moldability cannot be obtained, and as a result, it is difficult to obtain a high-performance product. . In the method for producing a zirconium oxide powder in the present invention, first, the concentration of the hydrated zirconia suspension is converted to about 10 to about 200 by converting the hydrated zirconia in the hydrated zirconia suspension into ZrO _2.
0 g / liter, preferably 10 to 100 g in terms of the converted value
Prepare in the range of 1 / liter.

The concentration of the hydrated zirconia suspension is not unique due to drying conditions and the like. In the present invention, the hydrated zirconia suspension is obtained by a method of hydrolyzing a water-soluble zirconium salt. The reason is that particles having powder characteristics are easily obtained. The hydrated zirconia suspension is preferably prepared by a hydrolysis method of an aqueous solution of zirconium oxychloride. The hydrated zirconia suspension may be a suspension to which a stabilizer such as yttria, magnesia, and calcia is added, that is, a suspension in which a stabilized or partially stabilized zirconia powder is formed after calcination. There is no limitation on the method of addition.

In the present invention, the hydrated zirconia particles in the hydrated zirconia suspension have a crystallite diameter of 5 nm or less.
The particles having a primary particle diameter of 50 to 150 nm are used. The hydrated zirconia suspension is dried.

[0011] The hydrated zirconia suspension is preferably spray-dried. In the case of a drying method other than spray drying, for example, in the case of static drying, the dried powder becomes block-shaped, and it is difficult to perform heat treatment by calcining uniformly. The loss is large. The drying temperature may be a commonly used temperature, preferably 50 to 250 ° C, and more preferably 100 to 200 ° C. Before the drying, an organic compound or a surface treating agent may be added to control the powder characteristics of the hydrated zirconia dry powder.

As the organic compound, alcohols, esters, surfactants and the like are preferably used. In particular,
Alcohols having 1 to 10 carbon atoms are preferred. The amount of the organic compound to be added is preferably in the range of 0.01 to 10 mol% based on the Zr containing the organic compound in the hydrated zirconia suspension, and is preferably in the range of 0.01 to 1 mol% based on the Zr. More preferred. Further, if necessary to facilitate the drying, the viscosity of the hydrated zirconia suspension is adjusted before the drying. The viscosity is preferably adjusted so that the viscosity of the hydrated zirconia suspension solution is about 50 to 5000 cP. The viscosity may be adjusted with an acid or an alkali, or a coagulant, a surfactant, an organic polymer, or the like may be added.

The hydrated hydrated zirconia powder preferably has a light bulk density of 1.0 to 2.0 g / cm ³ . The bulk density is more preferably from 1.2 to 1.8 g / cm ³ , even more preferably from 1.3 to 1.5 g / cm ³ . The water content of the hydrated zirconia dry powder is 1
It is preferably at most 5%, more preferably at most 10%.

Further, if necessary for controlling the powder characteristics after calcination, an alkali metal salt such as NaCl or NaOH or a caustic alkali may be added. In the present invention,
As Cl chlorine atom content of the dry powder of the calcined before the relative ZrO _2, there is preferably 1 to 20 wt%.
The dried hydrated zirconia powder is calcined. The calcination may be performed by a normal method such as no pressurization in an oxygen atmosphere.

The heating rate in the calcination step is 2 ° C./min.
The following is preferred. In the region where the calcination temperature is 700 ° C. or less, 1
The temperature is preferably 1 ° C. or less per minute, more preferably 0.5 ° C. or less. Further, in a region where the calcination temperature exceeds 700 ° C.,
The heating rate is preferably 2 ° C. or less per minute. The calcination temperature is preferably 900 to 1300 ° C.,
0 ° C. is more preferred. The holding time at the calcining temperature is preferably 1 hour or more, and more preferably 2 hours or more. The generated zirconium oxide powder is washed and crushed as necessary, and then crushed if necessary.

In the cleaning, the value obtained by converting impurity atoms such as alkali metal atoms and metal atoms other than zirconium and the stabilizing compound into oxides is preferably 2,000 ppm or less, more preferably not more than 2000 ppm with respect to the value obtained by converting contained Zr to ZrO _2. Preferably 1000 ppm or less, more preferably 600 ppm
It is good to wash until the following. The disintegration is performed to disintegrate the weakly aggregated coarse particles. Grinding is the usual method,
It is preferable to pulverize with a medium mill, a vibration mill, a ball mill or the like. After the crushing, preferably, the zirconium oxide suspension is spray-dried.

[0017]

Industrial Applicability The zirconium oxide powder of the present invention exhibits industrially good formability and, by sintering the formed body, has higher performance and higher reliability than conventional ones in terms of density, strength, etc. Zirconium oxide particles from which a sintered zirconium oxide sintered body can be obtained.

[0018]

【Example】

3 _mol% in terms of Example _{1 Y 2 O 3 (Y 2} O 3 in terms of value and Zr
O ₂ in terms of value to the sum of the. The same applies to the following)
including l _3, after boiling hydrolyzing zirconium oxychloride aqueous solution of ZrO ₂ concentration in terms 50 g / liter, the Z
Concentration was performed until the concentration in terms of rO ₂ became 300 g / liter, and a suspension of hydrated zirconia particles having an average primary particle diameter of 100 nm (by a particle size distribution analyzer using a photon correlation method) and a crystallite diameter of 4 nm. A liquid was obtained. The solution was spray-dried with a spray drier. The obtained dried particles were spherical and had a light bulk density of 1.25 g / cm ³ . The dried powder was calcined. Calcination is performed at a heating rate of 1 ° C./min. After that, the temperature was raised at a rate of 1.5 ° C./min. And kept at 1050 ° C. for 2 hours to obtain zirconium oxide powder. When the slurry was cast and press-molded using the obtained powder,
Good moldability was exhibited.

Example 2 The calcination conditions were up to 500 ° C. at a rate of 1 ° C./min. so,
Thereafter, until 950 ° C., the temperature was raised at a rate of 1.5 ° C./min. , And kept at 950 ° C. for 2 hours under the same conditions as in Example 1.

Example 3 The calcination conditions were up to 500 ° C. at a rate of 1 ° C./min. so,
Thereafter, the temperature was raised to 1250 ° C. at a rate of 1.5 ° C./min. , And maintained at 1250 ° C. for 2 hours under the same conditions as in Example 1.

[0021] 3 _mol% in terms of Comparative Example _{1 Y 2 O 3 (Y 2} O 3 in terms of value and Zr
O ₂ in terms of value to the sum of the. The same applies to the following)
including l _3, after boiling hydrolyzing zirconium oxychloride aqueous solution, and concentrated to an average primary particle diameter of 140 nm (according to particle size distribution measuring apparatus according to photon correlation spectroscopy), hydrated crystallite size of 6nm A suspension of zirconia particles was obtained. After the solution was dried, it was calcined under the same conditions as in Example 1 to obtain a zirconium oxide powder. When slurry casting was performed using the obtained powder, the gypsum casting mold was clogged and a good molded product could not be obtained.

Comparative Example 2 After boiling hydrolysis, the mixture was concentrated and the average primary particle diameter was 10%.
nm (by a photon correlation particle size analyzer) to give a suspension of amorphous hydrated zirconia particles. After the solution was dried, it was calcined under the same conditions as in Example 1 to obtain a zirconium oxide powder. Table 1 shows the powder properties of the powders obtained in the examples and the comparative examples. The zirconium oxide powders obtained in Examples and Comparative Examples were subjected to a pressure of 700K.
It was molded to 57 mm × 34 mm × about 5 mm at g / cm ² . By firing at 1500 ° C. for 2 hours after molding, a sintered body was obtained. After measuring the sintered body density by the Archimedes method, from the obtained sintered body, 3 mm × 4 mm × about 40 m
m test piece was cut out, and the room temperature three-point bending strength was measured by the method specified in JIS1601. Table 2 shows the average results of the 30 samples.

Table 1 Powder properties Average particle size BET specific surface area Cumulative distribution (%)(Μm) (m ² /g)≦0.1 μm> 10 μm> 5 μm Example 1 0.8 6.2 0.6 0 0.6 Example 2 0.5 9.3 0.9 0 1.0 Example 3 0.7 5.6 0.4 0.5 0.9 Comparative Example 1 0.8 15.2 6.5 0 0.5 Comparative Example 2 1.5 7.7 1.2 3.2 8.1 Table 2 Sintered Body Density and Room Temperature Three-Point Bending Strength Sintered Body Density Room temperature 3-point bending strength ^{(G / cm3) (kgf /} mm 2)  Example 1 6.09 125.7 Example 2 6.05 120.1 Example 3 6.07 122.3 Comparative Example 1 6.05 115.8 Comparative Example 2 5.89 99.5

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 25/02 C04B 35/48 CA (STN)

Claims (2)

(57) [Claims] 1. A BET specific surface area of 1 to 10 m ² / g, an average particle diameter of 0.1 to 1 μm, and a cumulative distribution of 0.1 to 1 m ² / g.
5% or less of particles less than μm and more than 10 μm
A zirconium oxide powder characterized by the following. 2. A crystallite having a crystallite diameter of 5 obtained by boiling hydrolysis.
The method for producing a zirconium oxide powder according to claim 1, wherein a suspension of the hydrated zirconia particles having a primary particle diameter of 50 to 150 nm or less is dried and calcined.