JPS61141619A - Production of zirconia fine powder - Google Patents

Abstract

PURPOSE:To produce zirconia fine powder containing uniformly dispersed stabilizer, by heating an aqueous solution containing dissolved Zr and sulfate radical to form an insoluble precipitate composed mainly of basic Zr sulfate, wherein a specific stabilizer is adsorbed to the precipitate during the formation of the precipitate. CONSTITUTION:One or more water-soluble compounds selected from Y compound, Ca compound, Mg compound Al compound and rare earth element compound and a water-soluble Zr compound are dissolved in water to obtain an aqueous solution containing sulfate radical. The solution is heated to obtain a pulpy mixture of the precipitate composed mainly of basic Zr sulfate. The pH of the mixture is raised to >=8 by the addition of an alkaline substance. The pulpy mixture is separated into solid and liquid, and the solid substance is optionally washed with an alkali, dried, and calcined to obtain the objective zirconia fine powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing fine zirconia powder, particularly partially stabilized or stabilized zirconia fine powder.

[Conventional technology]

Zirconia powder is a powder of zirconium oxide, and it is a substance that has become important in terms of its heat resistance properties, especially in the recent field of fine ceramics, and this powder is usually used for sintering. .

When zirconia powder is fired, it becomes a sintered body mainly consisting of tetragonal crystals, but as the powder particle size increases, and in the case of zirconium oxide alone, a phase transition occurs during the process of cooling to room temperature. % volume expansion becomes normal. This change in the volume of the fired crystal is not desirable in the production of precision fired crystals, not only in terms of dimensional changes but also in terms of strength and toughness.

Traditionally, yttrium oxide, calcium compounds, magnesium compounds, and aluminum compounds.

Partially stabilized zirconia powder containing a small amount of a stabilizer such as a rare earth element compound, or stabilized zirconia powder containing a relatively large amount of a stabilizer (hereinafter collectively referred to as stabilized zirconia powder) is commonly used. . When an appropriate amount of such a stabilizer is mixed.

The transition energy from tetragonal to monoclinic is stored inside, making it possible to create a sintered body with high strength and high toughness.
Furthermore, if a large amount of stabilizer is blended, it is possible to obtain sintered crystals without phase transition.

In this case, the conditions are that the zirconia powder is sufficiently fine and that the stabilizer is uniformly dispersed. Conventionally, as a method for producing such stabilized zirconia powder, a solution in which a stabilizer such as indolium is dissolved in an aqueous zirconium solution is used as a starting material.

(l) A method of coprecipitating by adding an alkali such as aqueous ammonia.

(2) A method in which the precipitate is hydrolyzed and then replaced in an organic solvent.

(3) A method of hydrolysis under high temperature and high pressure.

(4) A method of synthesizing an alkoxide compound and hydrolyzing it.

etc. were proposed.

[Problem that the invention seeks to solve]

The present invention solves the following problems in conventional methods for producing zirconia powder.

In the case of method T1), the obtained hydroxide is hard.

It takes a lot of grinding to make it into a fine powder. In method (2), the rate of hydrolysis is slow, requiring about 100 hours, and requires equipment for recovering organic solvents and explosion-proof equipment, resulting in high energy costs. Method (3) requires an autoclave and increases equipment and energy costs. Furthermore, method (4) involves a process of synthesizing an organometallic compound, which requires considerable chemical costs. The purpose of this study is to develop an economical method for producing stabilized zirconia fine powder that can be easily sintered even after pulverization.

[Means for solving problems]

The present invention provides a method for producing stabilized zirconia fine powder that effectively solves the above problems.

An aqueous solution containing at least one water-soluble compound of an indolium compound, a calcium compound, a magnesium compound, an aluminum compound, or a rare earth element compound and a water-soluble zirconium compound and containing a sulfate group. Prepare.

By increasing the temperature of this aqueous solution, an insoluble precipitate (substantially a precipitate of zirconium basic sulfate) is formed from the solution.
was precipitated to obtain a pulp in which this precipitate was dispersed.

An alkaline substance is added to this pulp to adjust the pH of the pulp liquid.
After setting it to 8 or more.

The pulp is subjected to solid-liquid separation to collect the solid material, which is dried with or without alkaline washing and calcined.

The present invention provides a method for producing fine zirconia powder consisting of the following.

The method of the present invention will be explained in detail below.

The most characteristic solution employed in the present invention is that an insoluble precipitate consisting mainly of zirconium basic sulfate is generated by simply heating an aqueous solution in which zirconium is dissolved and sulfate radicals are present, and this zirconium Utilizing the property of basic sulfate having ion adsorption ability, at least one of yttrium, calcium compounds, magnesium, aluminum, or rare earth elements is adsorbed to the precipitate during the formation of the precipitate; After generation, adjust the pH to yttrium, calcium, magnesium, aluminum,
Alternatively, at least one rare earth element may be fixed to the precipitate.

In carrying out the present invention, first.

Water Soluble Zirconium Compound 9 For example, at least one water soluble compound of a stabilizing element such as zirconium oxychloride, zirconium oxynitrate, etc.

Water-soluble indolium compound 1 such as yttrium chloride,
Yttrium nitrate, yttrium sulfate, etc.; Water-soluble calcium compounds 1, such as calcium chloride, calcium nitrate, etc.; Water-soluble magnesium compounds 9, such as magnesium chloride,
Magnesium nitrate, etc.; Water-soluble aluminum compound 2, such as aluminum chloride,
Aluminum nitrate, aluminum sulfate, etc.; water-soluble rare earth element compounds 1, such as rare earth element chlorides, nitrates, sulfates, etc.: are dissolved in water, and ammonium sulfate, sodium sulfate, magnesium sulfate, sulfuric acid are added as sulfate group regulators. Aluminum etc. are added, and the zirconium concentration in the liquid is 0.1 to 1.0 'sol/It, and the sulfate group concentration in the liquid is 0.4 to 0 per zirconium concentration 1 o + ol.
．． An aqueous solution containing substantially no solid substance is prepared so as to have a concentration of about 8 mol. The preparation operation of this aqueous solution is carried out at a temperature of 30° C. or below. If the solution is prepared within this temperature range, the solution will remain transparent even when a sulfuric acid group serving as a precipitant is added, and the formation of precipitates will be suppressed. In the present invention, it is first important to obtain an aqueous solution in which at least one of yttrium, calcium, magnesium, aluminum, and rare earth elements is completely dissolved in addition to zirconium and contains sulfate radicals. The pH of this aqueous solution is usually 2 or less.

When this transparent aqueous solution is heated, the solution becomes cloudy as the temperature rises, and when the temperature reaches about 80° C. or higher, zirconium basic sulfate completely precipitates. This mutually generated precipitate hardly dissolves again even if the temperature of the liquid is lowered, and therefore a bulb in which this insoluble precipitate is dispersed can be obtained simply by heating operation.In the case of the present invention Since the precipitate is generated only by heating, the precipitate that is formed is uniform in all parts of the liquid, and the pH during precipitate formation does not change, resulting in a highly uniform fine grain. You can get something. The heating operation is sufficient under atmospheric pressure.

This zirconium basic sulfate has the general formula.

This precipitate is expressed as (ZrO) n (SO4) ta ·x HzO, and has the property of adsorbing metal ions. Therefore, indium ions, which are precursors of zirconia powder stabilizers (indolium oxide, calcium oxide, RR magnesium, aluminum oxide, rare earth element oxides, etc.), calcium ions, magnesium ions, When aluminum ions, rare earth element ions, etc. are dissolved, these ions are adsorbed to the precipitate during or after the precipitate is formed. The point is that an insoluble precipitate of zirconium basic sulfate, which determines the particle shape, is generated only by a heating operation without pH fluctuation, and at the same time, yttrium, calcium, magnesium, aluminum, rare earth elements, etc. are adsorbed to this precipitate. This is a major feature of the present invention.

Next, an alkaline substance is added to the valve thus obtained, and the pH of the pulp liquid is finally adjusted to 8 or higher. pHm due to the addition of this alkaline agent
By this process, yttrium, calcium, magnesium, aluminum, rare earth elements, etc. still dissolved in the liquid can be co-precipitated as hydroxides into the zirconium compound, and the sulfate group can be converted from the zirconium basic sulfate to parenterized sulfate groups. You can let go. For example, when an alkaline substance such as ammonia water or ammonia gas is added to the valve so that the pH becomes 9 or higher, yttrium, calcium, magnesium, aluminum, rare earth elements, etc. in the liquid become hydroxides and are added to the precipitate. Fixed. Also, by adding this alkali, sulfate radicals can be removed from the precipitate.

To remove the sulfate radicals, an alkaline agent may be added to the pulp, but washing water with a pH of 8 or higher should be prepared.

In practice, it is preferable to perform decant washing of the pulp or filtration washing of the pulp with this washing water. By carrying out such washing with an alkaline solution until no sulfate radicals are detected in the washing solution, the sulfuric acid radicals can be effectively removed. The fine particles from which the sulfate group has been removed and the liquid separated by solid-liquid separation are zirconium hydroxide Zr.
O(OH) 2, indolium hydroxide Y (OR
) 3 Calcium hydroxide Ca (OR) 21
It is thought that magnesium hydroxide Mg (OH) 2 , aluminum hydroxide ^1(OH) 3 , rare earth element hydroxide, etc. are fixed.

After drying, the fine particles of hydroxide can be made into a stabilized zirconia fine powder by subjecting them to a conventional calcining treatment.

It has been found that the average particle diameter of this zirconia fine powder product has a predetermined relationship with the sulfate radical concentration when obtaining the aqueous starting solution. Therefore, by adjusting the sulfate radical concentration, the particle size of the zirconia fine powder product can be adjusted. Further, the crystallite size in the particles of the zirconia fine powder can be adjusted by adjusting the heating temperature during calcining.

Table 1 shows how y2 o3 is converted to 3 ggo1 according to the method of the present invention.
The graph shows the average particle size and tetragonal crystal ratio of zirconia powder when the sulfate group concentration of the aqueous solution which is the starting solution was changed when producing zirconia powder mixed in %.

Further, Table 2 shows the relationship between the heating temperature during calcination, the crystallite diameter, and the specific surface area when zirconia powder containing the same <Y2O3 at 3so1% is produced.

As is clear from Table 1 and Table 2, the particle size of the zirconia powder in the final product tends to increase as the concentration of sulfate groups in the aqueous solution increases, and when trying to obtain a fine particle size, 9 For example 1μ
If you want to obtain a particle size smaller than Ugly, use Sot/ZrO2
The concentration of sulfate radicals may be adjusted to a molar ratio of 0.5 or less. In the case of this fine grain size, the tetragonal crystal ratio can be increased even if the amount of ittriya is constant. Also.

As shown in Table 2, the crystallite diameter and specific surface area can be adjusted by adjusting the calcination temperature.

The amount of yttriya added to zirconia powder as a stabilizer can be adjusted by dissolving the required amount of yttrium as a stabilizer in the initial aqueous solution. In addition to being able to fix indium hydroxide, this yttrium can also be fixed in a uniformly dispersed state in each of the fine particles.

As described above, according to the method of the present invention, in the first step of the wet process, only an alkaline agent is required as a regulator used in addition to the raw materials, and precipitation is only caused by heating the liquid, which does not affect the pH. Since no equipment is required, this process can be carried out very economically, and since the fine particles obtained are hydroxides from which the sulfuric acid groups have been separated, sulfur dioxide gas is not emitted during the process of calcining them into zirconia. It is also advantageous in that it does not occur. Furthermore, the particle size and tetragonal crystal ratio of the final product zirconia powder can be well adjusted, as well as the amount of other stabilizing agents blended, and the zirconia fine powder has a small average particle size and the stabilizer is evenly dispersed. can be manufactured advantageously.

〔Example〕

Example 1 Zirconium oxychloride (Zr0C1z ・8) +20
) was dissolved in pure water, and the ZrO2 concentration was 310.9.
1001 g/l solution was obtained and used as a stock solution. Take 12.871 of this liquid and separately add yttrium oxide (Y203
99.9%) was weighed, 226.9g was dissolved in hydrochloric acid to make yttrium chloride, and mixed with a yttrium solution, which was diluted with water to make the total amount 80 β. The ZrO2 concentration at this time was 50 g/l. To this liquid, 1928 gr of ammonium sulfate was added in solid form and stirred to obtain a transparent mixed solution. Heat this liquid to a temperature of 80-85℃
The mixture was maintained at a temperature of 100 mL to form a precipitate, and the precipitate-forming reaction was completed.

Aqueous ammonia was added to the pulp liquid thus obtained to adjust the pH of the liquid to 9 or higher. Then filter the precipitate,
This precipitate was washed with a washing solution whose pH was adjusted to 9 or higher.

This is then dried and calcined at a temperature of 900°C to form Y2O.
Stabilized zirconia fine powder containing 3 mo1% of 3 was obtained. The physical properties of this fine powder are a bulk density of 0.43 g/d.

Tap density 0.90 g/aJ, average particle size 0.32
The μ-9 specific surface area was 24//gr, and the tetragonal crystal ratio was 97%.

When this fine powder was briefly molded and sintered at 1450°C, a pure white sintered body with a density of 5.95 g/d was obtained. When the powder was pulverized and then sintered at 1500°C, the density of the sintered body was 6.05 g/-.

Example 2 Take 12.872 grams of the zirconium stock solution prepared in Example 1, mix it with a yttrium solution in which 226.9 grams of yttrium oxide was weighed and dissolved in hydrochloric acid to make yttrium chloride, and diluted with water to make up the entire amount. It was set to 801. The ZrO2 concentration of this liquid is 50 g/jt.

To this liquid, 2357 gr of ammonium sulfate was added as a solid and stirred to obtain a transparent mixed solution.

This liquid was heated and the liquid temperature was maintained at 80 to 85°C to form a precipitate, thereby completing the precipitation reaction. The time required up to this point was approximately 5 hours.

Aqueous ammonia was added to the pulp liquid thus obtained to adjust the pH of the liquid to 9 or higher. Then filter the precipitate,
This precipitate was washed with a washing solution having a pH of 9 or higher.

Next, this was dried and calcined at a temperature of 900°C to form Y2O.
A stabilized zirconia fine powder containing 3-01% of No. 3 was obtained. The physical properties of this fine powder are a bulk density of 0.69 g/ai.

Tap density 1.47 g/d, average particle size 1.23μ
m.

The specific surface area was 22 td/gr, and the tetragonal crystal ratio was 74%.

When this fine powder was sintered at 1450° C. for 2 hours, the sintered density was 5.56 g/d. In addition, the fine powder was
When pulverized with a time vibration mill and sintered at 1500°C, the density of the sintered body is 6.01 g/aJ,
The tetragonal crystal ratio of this sintered body was 98%.

Example 3 Take 12.871 g of the zirconium stock solution prepared in Example 1 and add 190 g of anhydrous calcium chloride to the solution to bring the liquid volume to 80 j! Then, 192.8g of ammonium sulfate was added to this mixed solution without heating. At that time, the liquid becomes completely clear.

No gypsum precipitation was observed. When ammonium sulfate was completely dissolved, heating was started, and the temperature was maintained at 80 to 85°C for 2 hours to form a precipitate and complete the precipitation reaction. Aqueous ammonia was added to the pulp liquid thus obtained to adjust the pH of the liquid to 10 or higher. Then, the precipitate was filtered, and the precipitate was washed with a washing liquid adjusted to have a pH of 10 or higher.

Next, this was dried and calcined at a temperature of 900°C to produce Ca.
O-stabilized zirconia fine powder was obtained. The physical properties of this fine powder include an average particle size of 1.20 μm and a bulk density of 0.70 g/d.
, tap density 1.12 g/cg1. Specific surface area 22r
d/g *Tetragonal crystal ratio 52%, sintered density at 1600℃ 5.65 g/aj, transverse rupture strength 7.0ksr/m
It was 2.

Example 4 Magnesium chloride (MgC
Same treatment as Example 3 except that 587 gr of 1z 6H20) was added. A 1gO stabilized zirconia fine powder was produced. The physical properties of the obtained fine powder are as follows: average particle diameter: 0.35μ steel, bulk density: 0.39 g/d, tap density: 0.84
g/cd, specific surface area 20 rd/g, tetragonal crystal ratio 35%
.

The sintered density at 1600° C. was 5.43 g/aj, and the transverse rupture strength was 18 dazzles/tsuru 2.

Claims (1)

[Scope of Claims] At least one water-soluble compound selected from a yttrium compound, a calcium compound, a magnesium compound, an aluminum compound, or a rare earth element compound and a water-soluble zirconium compound are dissolved in water, and a sulfuric acid radical is dissolved in water. An insoluble precipitate is precipitated from the solution by increasing the temperature of the aqueous solution to obtain a pulp in which the precipitate is dispersed, and an alkaline substance is added to the pulp to adjust the pH of the pulp liquid.
8 or higher, the pulp is solid-liquid separated to collect a solid substance, the solid substance is dried with or without alkaline washing, and then sintered. .