JP3146578B2 - Manufacturing method of zirconia fine powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing zirconia powder, which is a raw material for zirconia ceramics, and more particularly to a method for producing a zirconia fine powder capable of improving the formability of the raw material powder. .

[0002]

2. Description of the Related Art Conventionally, as a method for producing zirconia powder, ammonia water is added to a suspension of hydrated zirconia fine particles in which a stabilizer is dissolved, and the zirconia powder is filtered, washed with water, and calcined. (JP-A-63-129017) A method in which a chloride stabilizer is added to a raw material of zirconium hydroxide and calcined to obtain zirconia powder (JP-A-61-266307). Zirconyl ammonium carbonate A method in which hydrogen peroxide is added to a mixed aqueous solution of a salt and a stabilizer, and the obtained solid is dried and calcined to obtain a zirconia powder (Japanese Patent Laid-Open No. 61-4761).
17 gazette) are known.

[0003]

The zirconia powder obtained by the above method is a fine powder having a very large BET specific surface area, that is, a fine powder having a small particle size. Since the adhesive force between them significantly increases, the obtained zirconia powder becomes a strong agglomerated powder, which makes it difficult to mold. The zirconia powder obtained by the above method is calcined at 1100 ° C. with a gel-like precipitate of zirconium hydroxide, and when this gel-like precipitate is calcined at a high temperature, strong agglomeration between particles occurs violently. And poor dispersibility. Is to add hydrogen peroxide to a mixed aqueous solution of a zirconyl ammonium carbonate salt and a stabilizer, and calcinate the obtained gel-like coprecipitate to obtain zirconia powder. The precipitate has a heterogeneous composition, and the powder obtained for calcining the gel precipitate has poor dispersibility as described above. Further, hydrogen peroxide used in coprecipitation is a highly dangerous substance, which makes industrial mass production difficult and impractical.

In the present invention, such disadvantages in the conventional method are solved, that is, zirconia powder having a good dispersibility and a good dispersibility, in which a stabilizer is well dissolved, is produced by a simple process. The purpose is to provide a method that can do this.

[0005]

The present inventors calcinated a mixture of hydrated zirconia sol and a stabilizer commonly used in the production of zirconia-based ceramics, such as yttria, calcia, magnesia, and ceria, to produce zirconia. According to a detailed study focusing on the calcining atmosphere and the solid solution reaction when obtaining the powder, the stabilizer is controlled by controlling the thickness of the mixture layer when the mixture is charged into the calciner. It is possible to produce fine particles of zirconia which are sufficiently solid-dissolved and therefore have good dispersibility, and the fine powder thus obtained has good moldability and zirconia fine powder which is sintered at a relatively low temperature. The present invention was found to be a powder, and the present invention was completed.

The present invention relates to a hydrated zirconia sol and Y, C
a method of producing a zirconia fine powder by calcining a mixture containing at least one compound of a, Mg, and Ce, wherein the mixture having a layer thickness of H (cm) is 120H ^0.5 +50.
The gist of the present invention is a method for producing zirconia fine powder by calcining at a temperature T (° C.) satisfying the condition of 0 ≦ T ≦ 1200. Hereinafter, the present invention will be described in more detail.

In the present specification, the “solid solution reaction rate” relating to the solid solution reaction between the hydrated zirconia sol and the stabilizer is calculated by the following equation, focusing on the diffraction line measured by powder X-ray diffraction. It is something that is done.

[0008] Tetragonal crystal ratio (%) = It / (It + Ic + Im) × 100 Cubic crystal ratio (%) = Ic / (It + Ic + Im) × 100 where It is the intensity of the tetragonal (111) diffraction line, I
c is cubic (111) strength, Im is monoclinic (11).
It is the sum of the intensities of 1) and (11-1). The “average particle size” of the hydrated zirconia sol is determined by particle size measurement using an electron microscope or a particle size distribution analyzer, and is given by, for example, a photon correlation method.

The zirconia fine powder obtained in the present invention is B
The ET specific surface area is 5 to 25 m ² / g. When the BET specific surface area is less than 5 m 2 ^/ g, dispersibility good zirconia powder is not obtained to strong agglomeration due to sintering occurs between particles becomes greater than 25 m 2 / ^g, with between particles Due to the remarkable increase in the adhesive force, the powder becomes a strong agglomerated powder, is difficult to mold, and is not suitable as a ceramic powder. Further, the calcined powder obtained by calcining a mixture of the hydrated zirconia sol and the stabilizer preferably has a solid solution reaction rate of 90% or more, and if the solid solution reaction rate is lower than 90%, the zirconia fineness is reduced. The composition of the powder becomes non-uniform, and if such a powder is molded and fired, non-uniform shrinkage or the like due to abnormal grain growth is likely to occur, which is not preferable. More preferably, it is 95% or more. By the way, the above hydrated zirconia sol has an average particle size of 0.0
It is preferable that the diameter is 5 to 0.3 μm and the crystallite diameter is 4 nm or less. The average particle size of the hydrated zirconia sol is 0.0
If it is smaller than 5 μm, strong cohesion due to sintering between particles is likely to occur during calcination, and if it is larger than 0.3 μm, the particle size of the powder will be large and the sinterability will be low. It is not desirable as a powder. On the other hand, when the crystallite diameter is larger than 4 nm, the solid solubility with the stabilizer is reduced, which is not preferable.

In the present invention, when a mixture of a hydrated zirconia sol and a stabilizer is calcined, the layer thickness H (cm) and the calcining temperature T (° C.) of the mixture are 120H ^0.5 +500. The relationship of ≦ T ≦ 1200 must be satisfied. Calcination temperature is 120H
^{If the} temperature is lower than ^0.5 + 500, the solid solution reaction rate of the calcined powder becomes lower than 90%, so that a solid solution with the stabilizer cannot be obtained.
When the specific surface area is larger than 25 m ² / g, the desired zirconia fine powder cannot be obtained. On the other hand, 120
If the temperature is higher than 0 ° C., strong aggregation due to sintering between particles occurs, so that the BET specific surface area becomes smaller than 5 m ² / g, and zirconia powder having good dispersibility cannot be obtained. Furthermore, at such a high calcination temperature, industrial mass production is difficult and therefore impractical. A more preferable calcination temperature T (° C.) is the above (120H ^0.5 +5).
00) to 1200 ° C., and the relationship between the average particle diameter φ (μm) of the hydrated zirconia sol satisfies T ≧ 1000φ + 400, and more preferably, 1000φ + 400 ≦ T ≦ 3000φ + 600. Is satisfied. Various gases can be selected as the atmosphere gas during calcination. It is better that the gas used at this time contains water vapor, and the partial pressure of water vapor is 30 mm.
It is better to use a gas of Hg or more. If it is lower than 30 mmHg, since the grain growth of the hydrated zirconia sol during calcination is suppressed, it is difficult to obtain dense particles at a low temperature, which is not preferable. A more preferred partial pressure of water vapor is 40 to 760 mmHg. Examples of the type of gas include air, carbon dioxide, nitrogen, oxygen, argon, and helium. The holding time of the calcination temperature is preferably 0.5 to 10 hours, and the heating rate is 0.5 to 10 ° C /
min is preferred. If the holding time is shorter than 0.5 hours, it is difficult to uniformly calcine, and if the holding time is longer than 10 hours, the productivity is undesirably reduced. On the other hand, if the heating rate is lower than 0.5 ° C./min, the time required to reach the set temperature becomes longer. Is reduced.

The hydrated zirconia sol described above may be obtained under any reaction conditions. In the case of a hydrolysis reaction of an aqueous zirconium salt solution, the average particle size of the obtained hydrated zirconia sol can be controlled by adjusting the pH of the reaction solution at the end of the reaction. For example, by adjusting the pH at the end of the reaction to be 0.1 to 1.5, a hydrated zirconia sol having an average particle size of 0.05 to 0.3 μm can be obtained. On the other hand, the crystallite diameter can be controlled by adjusting the anion concentration of the zirconium salt aqueous solution, and the anion concentration is adjusted to 0.8 g ion / l.
When hydrolyzed as described above, a hydrated zirconia sol having a crystallite diameter of 4 nm or less is obtained. Therefore, a desired hydrated zirconia sol can be obtained by controlling the anion concentration and pH of the aqueous zirconium salt solution within the above ranges. Methods for controlling the pH and anion concentration, that is, the average particle size and crystallite of the hydrated zirconia sol, include, for example, adding an acid, alkali, or metal salt to a zirconium salt aqueous solution, or anion exchange. A method of hydrolyzing by adjusting the pH by removing a part of the anion constituting the zirconium salt with a resin,
Alternatively, a mixed slurry of zirconium hydroxide and an acid, and a metal salt added to the mixed slurry to form a mixed slurry p
A method of adjusting the concentration of H and anions to carry out hydrolysis is exemplified. Here, examples of the zirconium salt used in the production of the hydrated zirconia sol include zirconium oxychloride, zirconyl nitrate, zirconium chloride, zirconyl sulfate, and the like. Is also good. Examples of the alkali added to control the average particle size of the hydrated zirconisol include ammonia, sodium hydroxide, potassium hydroxide, and the like. In addition, the alkali decomposes like urea to show basicity. It may be a compound. Examples of the acid include hydrochloric acid, nitric acid, sulfuric acid and the like, and in addition, organic acids such as acetic acid and citric acid may be used. Further, examples of the metal salt to be added for controlling the anion concentration of the aqueous zirconium salt solution, that is, the crystallite size of the hydrated zirconisol, include salts of alkali metals or alkaline earth metals such as sodium salts, and aluminum salts. However, an ammonium salt may be added. When a raw material of zirconium hydroxide is used, various methods can be selected for its production method. For example, zirconium hydroxide can be obtained by neutralizing an aqueous solution of zirconium salt with an alkali.

The mixture of the hydrated zirconia sol and the stabilizer obtained by this reaction can be obtained by drying the hydrated zirconia sol-containing liquid containing the stabilizer. There is no particular limitation on the method for drying the liquid content. For example, the suspension or a method in which an organic solvent is added to the suspension to dry it, an alkali is added to the suspension, and the suspension is filtered, washed with water, and dried And the like. The bulk density of the resulting mixture at this time is preferably in the range of 0.5~2.1g / cm ^3. When the bulk density is larger than 2.1, the atmosphere in the mixture becomes uneven during calcination, so that the solid solubility with the stabilizer is deteriorated. When the bulk density is smaller than 0.5, the production efficiency is reduced. Not preferred. More preferred bulk density is 0.9~1.6g / cm ^3. The mixture contains 1% by weight based on zirconia.
It is better to include the above anions. If the anion content is lower than 1%, the grain growth rate of the hydrated zirconia sol during calcination becomes slow, so that it is difficult to obtain dense particles at a low temperature. More preferred anion content is
3 to 33%. The stabilizer may be added to the suspension after hydrolysis, or may be added in advance at the time of hydrolysis. The amount of the stabilizer added is 1 to 1 in terms of zirconia in the hydrated zirconia sol.
30 mol% is preferable, and the type is Y, Ca, Mg,
Any compound such as Ce may be used. Particularly, water-soluble salts, hydroxides, oxides, and the like are preferable. of course,
If necessary, a compound such as aluminum or a transition metal may be added before drying.

[0013] The calcined powder obtained as described above is pulverized into a finely dispersed zirconia fine powder.

[0014]

The microstructure of a hydrated zirconia sol obtained by hydrolysis of an aqueous solution of a zirconium salt is observed by an electron microscope to be composed of particles in which ultrafine particles having good crystallinity are aggregated. It is considered that the smaller the size of the ultrafine particles, the larger the reaction surface area with the stabilizer and the better the uniformity with the stabilizer. From this, it is inferred that the reaction surface area is affected because the atmosphere near the particles changes as the mixture becomes thicker by calcining, and as a result, the solid solubility with the stabilizer changes.

[0015]

As described above, according to the present invention, according to the present invention, a fine particle in which a stabilizer is well-dissolved and has good dispersibility,
Therefore, zirconia powder having good moldability can be manufactured by a simple process.

[0016]

The present invention will be described below in detail with reference to examples. In the examples, the crystal structure of the hydrated zirconia sol is monoclinic, and its crystallite diameter was calculated by applying the Scherrer equation to the half width of the diffraction line of (11-1). Here, the Scherrer constant was set to 0.9. The zirconia fine powder was molded by a mold press at a molding pressure of 700 kg / cm ² , and the molded body was sintered at 1500 ° C. for 2 hours.

Example 1 To 2.5 liters of a 2 mol / l aqueous solution of zirconium oxychloride, 2 liters of 1N ammonia water, 36 g of yttrium oxide and 7.5 g of sodium chloride were added.
Distilled water was further added to prepare 10 liter of a 0.5 mol / l zirconium oxychloride aqueous solution. The hydrolysis reaction was performed at the boiling temperature for 120 hours while stirring the raw material liquid. The average particle size of the obtained hydrated zirconia sol according to the photon correlation method is 0.1 μm, and the crystallite size is 2.4 n.
m. This hydrated zirconia sol-containing liquid is heated and concentrated, and further spray-dried to obtain a bulk density of 1.3 g / cm.
^{3. A} hydrated zirconia dry powder having a chlorine content of 15% (weight ratio to zirconia, the same applies hereinafter) was prepared. This dried powder was charged into a calciner with a layer thickness of 6 cm, and a partial pressure of water vapor of 10 cm.
It was calcined at a temperature of 850 ° C. for 2 hours in air of 0 mmHg (120 × 6 ^0.5 + 500 = 794). As a result of measuring the powder X-ray diffraction of the obtained calcined powder, it was a tetragonal diffraction pattern and the solid solution reaction rate was 97%.

Next, the calcined powder obtained above was washed with water, and then ground with a ball mill for 50 hours. The BET specific surface area of the obtained zirconia fine powder was 15 m ² / g. When a compact was produced using this powder, the compact had a density of 2.67 g / cm ³ , and the sintered compact obtained by firing this compact had a density of 6.07 g / cm ³ ,
The bending strength was 115 kgf / mm ² .

Example 2 The same procedure as in Example 1 was carried out except that the calcining temperature was set at 700 ° C. and the layer thickness of the dried powder was set at 2.5 cm (120 × 2.5
^0.5 + 500 = 690).

The solid solution reaction rate of the obtained calcined powder was 92%, and the BET specific surface area of the zirconia fine powder after washing with water and pulverizing was 23 m ² / g. Using this powder,
When a molded article was produced, the density of the molded article was 2.75 g / c.
m ³ , the density of the sintered body obtained by firing this compact was 6.08 g / cm ³ , and the bending strength was 120 kgf / cm ² .
It was mm ^2.

Example 3 To 2 liters of a 2 mol / l zirconium oxychloride aqueous solution, 1.9 liters of 1N ammonia water and 36 g of yttrium oxide were added, and distilled water was further added to obtain 0.1 ml.
10 liters of a 4 mol / l zirconium oxychloride aqueous solution was prepared. The hydrolysis reaction was performed at the boiling temperature for 120 hours while stirring the raw material liquid. The average particle size of the obtained hydrated zirconia sol by the photon correlation method is 0.15 μm.
m, and the crystallite diameter was 2.6 nm. The hydrated zirconia sol-containing liquid was heated and concentrated, and further spray-dried to prepare a hydrated zirconia dry powder having a bulk density of 1.2 g / cm ³ and a chlorine content of 14%. This dried powder is 8c
m in a calcining furnace with a steam partial pressure of 100 mmHg
Calcined at a temperature of 900 ° C. for 2 hours (120 ×
^80.5 + 500 = 839). When the powder calcined powder obtained was measured for powder X-ray diffraction, only a tetragonal diffraction pattern was obtained, and the solid solution reaction rate was 98%.

Next, the calcined powder obtained above was washed with water and pulverized with a ball mill for 50 hours. The BET specific surface area of the obtained zirconia fine powder was 15 m ² / g. When a compact was produced using this powder, the compact density was 2.75 g / cm ³ , and the sintered compact obtained by firing this compact had a density of 6.09 g / cm ³ ,
The bending strength was 125 kgf / mm ² .

Example 4 To 2 liters of a 2 mol / l zirconium oxychloride aqueous solution, 3.6 liters of 1N aqueous ammonia and 28.5 g of yttrium oxide were added, and further distilled water was added to obtain 0.4 mol / l oxychloride. Zirconium aqueous solution 10
One liter was prepared. The hydrolysis reaction was performed at the boiling temperature for 120 hours while stirring the raw material liquid. The average particle size of the obtained hydrated zirconia sol by the photon correlation method was 0.2.
6 μm, and the crystallite diameter was 2.9 nm. The hydrated zirconia sol-containing liquid is heated and concentrated, and further spray-dried to obtain a bulk density of 1.0 g / cm 3 and a chlorine content of 13 g / cm 3.
% Hydrated zirconia dry powder was prepared. This dried powder was charged into a calciner at a layer thickness of 10 cm, and a partial pressure of steam was 40 mm.
Calcination was carried out at a temperature of 1000 ° C. for 2 hours in air of Hg (1
20 × 10 ^0.5 + 500 = 879). The obtained calcined powder was subjected to powder X-ray diffraction measurement. As a result, only a tetragonal diffraction pattern was obtained, and the solid solution reaction rate was 97%.

Next, the calcined powder obtained above was washed with water and pulverized with a ball mill for 50 hours. The BET specific surface area of the obtained zirconia fine powder was 8 m ² / g. When a compact was produced using this powder, the compact density was 2.70 g / cm ³ , and the sintered compact obtained by firing this compact had a density of 6.08 g / cm ³ , The bending strength was 120 kgf / mm ² .

Example 5 To 3 liters of a 2 mol / l zirconium oxychloride aqueous solution, 4 liters of 1N ammonia water and 36 g of yttrium oxide were added, and further distilled water was added to add 0.6 mol.
Per liter of an aqueous zirconium oxychloride solution was prepared. The hydrolysis reaction was performed at the boiling temperature for 120 hours while stirring the raw material liquid. The average particle size of the obtained hydrated zirconia sol by photon correlation was 0.1 μm,
The crystallite diameter was 2.5 nm. The hydrated zirconia sol-containing liquid was heated and concentrated, and further spray-dried to prepare a dried hydrated zirconia powder having a bulk density of 1.3 g / cm ³ and a chlorine content of 15%. This dried powder was charged into a calciner with a layer thickness of 6 cm, and was dried in air having a partial pressure of water vapor of 30 mmHg.
Calcined at a temperature of 00 ° C. for 2 hours (120 × 6 ^0.5 +5
00 = 794). As a result of measuring the powder X-ray diffraction of the obtained calcined powder, a tetragonal diffraction pattern was obtained, and the solid solution reaction rate was 98%.

Next, the calcined powder obtained above was washed with water and then pulverized with a ball mill for 50 hours. The BET specific surface area of the obtained zirconia fine powder was 20 m ² / g. When a compact was produced using this powder, the compact had a density of 2.88 g / cm ³ , and the sintered compact obtained by firing this compact had a density of 6.08 g / cm ³ ,
The bending strength was 125 kgf / mm ² .

Comparative Example 1 The same procedure as in Example 1 was performed except that the calcining temperature was set at 700 ° C. and the layer thickness of the dried powder was set at 6 cm (120 × 6 ^0.5 +5).
00 = 794).

The solid solution reaction rate of the obtained calcined powder was 80%, and the BET specific surface area of the zirconia fine powder after washing with water and pulverizing was 23 m ² / g. Using this powder,
When a molded body was produced, the molded body density was 2.59 g / c.
m ^3, the density of the sintered body obtained by firing the molded body, 5.95 g / cm ^3, flexural strength 96Kgf / m
It was m ^2.

Claims (1)

(57) [Claims] A hydrated zirconia sol and Y, Ca, Mg, C
e) calcining a mixture containing at least one compound out of e to produce fine zirconia powder, wherein the layer thickness H
(Cm) of the mixture is 120H ^0.5 + 500 ≦ T ≦ 1
A method for producing zirconia fine powder, comprising calcining at a temperature T (° C.) satisfying the condition of 200.