JPS60255622A - Production of fine powder of zirconia having excellent sinterability - Google Patents

Abstract

PURPOSE:To obtain the titled fine powder having high bulk density and excellent dispersibility, and giving a dense sintered material, by adding a polybasic carboxylic acid (salt) to a specific aqueous solution, and carrying out the thermal hydrolysis to form colloidal particles. CONSTITUTION:An aqueous solution containing a water-soluble Zr salt or its mixture with Mg, Ca or a >=3-valent element and having a Zr salt concentration of >=0.1mol%, is added with <=0.5mol (based on 1mol of Zr) of a polybasic carboxylic acid (salt) containing 2-4 carboxylic acid groups in 1mol. The mixture is hydrolyzed to produce colloidal particles by heating at >=50 deg.C for >=several hr. Before or after the formation of the colloidal particles, the mixtur is added with an alcohol having a boiling point of >=80 deg.C (e.g. ethanol) and thermally dehydrated to obtain the titled fine powder having particle diameter of <=300Angstrom .

Description

[Detailed description of the invention] This relates to a manufacturing method.

Zirconia fine powder is used in a wide range of applications, including refractories, abrasives, coating materials, painting, pigments, optical glasses, ferroelectrics, piezoelectrics, catalyst carriers, and solid electrolytes. In addition, in recent years, it has been discovered that partially stabilized zirconia, which is produced by adding a small amount of a stabilizer such as magnesia, calcia, or yttria to zirconia, has unprecedented high strength and toughness. Development in this field is rapidly accelerating, and its use as a variety of high-strength structural materials is expanding. For this reason, the demand for zirconia-based fine powder, which is the raw material, is also increasing.

The method of the present invention is aimed at producing fine zirconia powder suitable for such uses.

Conventionally, as a method for producing zirconia-based fine powder, a mixed solution of a water-soluble zirconium salt such as zirconium oxychloride and an aqueous solution of a metal element salt serving as a stabilizer such as magnesium chloride, calcium chloride, or yttrium chloride, Add an alkali such as ammonia water to neutralize and coprecipitate to generate a hydroxide sol, which is then filtered, washed,
The most common method was to dry and then calcinate.

However, the powder obtained by this method has a low bulk density and the primary particles are relatively fine and porous, so when made into a sintered body, the density is generally low and sufficient strength and hardness are obtained. The disadvantage was that it was difficult to get rid of.

Another typical method for producing zirconia-based fine powder is a hydrolysis method. In this method, a mixed aqueous solution of a water-soluble zirconium salt such as zirconium oxychloride and a salt of a metal element serving as a stabilizer such as magnesium chloride, calcium #i chloride, or yttrium chloride is directly heated and reacted with the solid solution type zirconia. A sol is produced as a precursor, and this is dried and calcined. The zirconia-based fine powder obtained by this method has a relatively high bulk density, the primary particle size is slightly larger, and fine and uniform secondary particles are easily obtained. For this reason, it has excellent sinterability and is characterized in that a dense sintered body can be obtained.

Since the zirconia fine powder produced by the above-mentioned neutralization method is manufactured by drying and calcining the generated hydroxide, in many cases micropores are likely to be generated due to the elimination of the water-bearing group, and when this is sintered, It is thought that the pores remain in the sintered body, making it difficult to obtain a high-density sintered body. On the other hand, in the hydrolysis method, fine zirconia crystals or their precursors are directly generated as colloidal particles from an acidic aqueous solution such as hydrochloric acid, and therefore a dense sintered body can be easily obtained.

However, this hydrolysis method has a very slow reaction rate, and the concentration of zirconium in the aqueous solution is about r1.6 mol/j.
At higher temperatures, the reaction does not proceed in a substantial sense. Therefore, it is necessary to react a low concentration zirconium salt aqueous solution of about (L5 mol/l or less) for a long time, for example, several days. It has the disadvantage of high cost because it requires a tank and the reaction efficiency is low.

Another method for producing fine zirconia powder is to use an alkoxide such as zirconium isoptepoxide as a raw material and hydrolyze it in an organic solvent, but in this case the cost of the raw material is high and the reaction is slow. Since it is complicated, the cost is high and it is industrially disadvantageous.

For these reasons, the present inventors have conducted extensive studies with the aim of developing a method for producing zirconia-based fine powder that has excellent sintering properties, is low cost, and is industrially advantageous.

As a result, by adding a small amount of polyhydric carboxylic acid and/or its salt to an aqueous solution of water-soluble zirconium salt and heating it, colloid-like particles are generated, and by drying and calcining, excellent sinterability is achieved. It was discovered that zirconia-based fine powder could be obtained, and the present invention was achieved.

The method of the present invention allows the use of a highly concentrated zirconium salt aqueous solution and allows the reaction to proceed in a short period of time, resulting in high reaction efficiency and is very industrially advantageous.

Water-soluble zirconium salts are generally thought to exist in a polynuclear complex ion state composed of several zirconium ions in an aqueous solution.

When heated, the polynuclear complex ions are dehydrated and polymerized to form a high molecular weight polymer, which is precipitated as colloidal particles, and the hydrolysis reaction progresses. Although the effect of the addition of polyvalent carboxylic acids used in the method of the present invention is not fully clear, it is clear that monocarboxylic acids such as acetic acid and propionate have no effect, and that the addition of a very small amount of polycarboxylic acids to zirconium It is thought that the reaction between the above-mentioned polynuclear complex ions is catalytically promoted and the hydrolysis reaction progresses.

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

Examples of the water-soluble zirconium salt used as a raw material in the method of the present invention include zirconium sulfate, zirconium nitrate, zirconium chloride, zirconium acetate, and zirconium oxychloride, with zirconium nitrate or zirconium oxychloride being preferred. The concentration of zirconium salt in the aqueous solution can be selected from a wide range;
In order to effectively carry out the method of the present invention, 0.1 mol/1
It is necessary to have a concentration of about [12 mol/l ~
A range of about 2 mol/l is more preferred. In addition, one or more elements having a valence of 3 or more, such as magnesium, calcium, aluminum, yttrium, lanthanum rare earths, silicon, titanium, hafnium, and transition metals, may coexist in the aqueous solution. In the method, effective polycarboxylic acids are polycarboxylic acids having from 2 to 4 carboxylic acid groups in one molecule. Therefore, specific examples of the polyvalent carboxylic acids to be added to the zirconium salt aqueous solution include Scheric acid, malonic acid, succinic acid, adipic acid, sebacic acid, maleic acid, and fumaric acid.

Examples include divalent carboxylic acids such as malic acid, tartaric acid, heptatalic acid, and terephthalic acid, trivalent carboxylic acids such as citric acid, itaconic acid, and trimellitic acid, and tetravalent carboxylic acids such as pyromellitic acid. Examples of the salt include alkali salts such as ammonium salts and sodium salts.

These polyhydric carboxylic acids or salts thereof may be added to an aqueous solution of a water-soluble zirconium salt in their original form, but it is more preferable to add them after dissolving them in water or the like.

The total amount of polyvalent carboxylic acid or its salt to be added must be less than α5 mol per 1 mol of zirconium; if it is more than this, polyvalent carboxylate of zirconium will be generated. The effects of the present invention cannot be obtained. The gist of the present invention is to catalytically promote the hydrolysis reaction by coexisting a small amount of polycarboxylic acid ions in an aqueous solution of a water-soluble zirconium salt. In order to produce a zirconia-based fine powder with excellent sinterability, which is the object of the present invention, it is important to generate colloid-like fine particles of Zirphere, which is a high-molecular polymer that is uniform and has a high degree of polymerization.

For this reason, the amount of polyhydric carboxylic acid or its salt to be added is
Concentration of zirconium in aqueous solution 1 Reaction temperature.

Although it varies greatly depending on the reaction time etc., it is preferably α005 to α5 mol per 1 mol of zirconium [L
It is particularly preferable that O1 to [1,3 mol.

The production of colloidal particles is significantly promoted by heating an aqueous solution of a water-soluble zirconium salt to which at least one of these polyhydric carboxylic acids or salts thereof is added. The preferred reaction temperature varies depending on other conditions, etc., but is usually about 50°C or higher, more preferably about 60°C to about 12°C.
It is preferable to set it in the range of 0°C.

The reaction time varies depending on the concentration of the zirconium salt, the type and concentration of the polyhydric carboxylic acid or its salt added, the reaction temperature, etc., but is usually several hours or more, preferably about 10 hours.
A range of hours to several tens of hours is appropriate.

Before or after the formation of colloidal particles, add an alcohol with a boiling point of 80°C or higher at normal pressure, such as propatool, butanol, amyl alcohol, hexanol or octatool, and heat or dehydrate by heating.
It can also facilitate drying and improve the dispersibility of the resulting powder particles.

Drying can be carried out by any method such as directly heating the reaction solution containing colloidal particles to dehydrate and concentrate it, freeze drying or spray drying. When drying by heating, the appropriate temperature is about 60°C or higher, more preferably about 0°C to about 200°C. The zirconia-based fine powder of the present invention can be obtained by further calcining this at a temperature of usually about 00°C to about 1000°C.

The zirconia-based fine powder thus obtained has a high bulk density and good dispersibility. In addition, the crystallite diameter is approximately 801 or less at the stage where normal drying is completed, and 900
Even when calcined at ℃, the particles are very fine with a diameter of about 500A or less.

The zirconia-based fine powder obtained by the method described above can be used as is and has good powder characteristics, but in order to obtain even better performance when made into a sintered body, the secondary particle size must be increased. Approximately 2
It is preferable to use it by crushing it to a particle size of about 1 μm or less, preferably less than 1 μm. The pulverization method may be either a dry method or a wet method, and can be carried out by any conventionally known method.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these. In addition, the bending strength shown in the examples refers to width of 4 mm, thickness of 3 mm,
It means the average value of the strength of five or more specimens obtained when a test specimen with a length of 40 mm is subjected to three-point bending failure under the conditions of a span length of 50 as and a crosshead speed (L5 mn/win).

Further, the density of the sintered body is determined by the commonly used underwater Archimedes method.

Example 1 Zirconium oxychloride (Zr0O]4.840) was dissolved in water, and the concentration of zirconium was 30 as Zr01.
An aqueous solution of zirconium salt weighing 4.6 g// was prepared. To this aqueous solution &071, add 7.5% water/and citric acid (H
1.61 of an aqueous solution in which 94.69 of OOO-000H (2% O) was dissolved was added. The concentration of zirconium in this mixed aqueous solution is 1.0 mol/l, and the number of moles of zirconium added is 1.0 mol/l. α05 moles per mole.

Pour this mixed aqueous solution into a glass container and stir for about 1 hour.
The mixture was heated at 00°C for 20 hours. After completion of the reaction, the generated sol was dehydrated under reduced pressure and heated at about 120°C under air circulation.
Dry for 0 hours. The apparent bulk density of the obtained dry powder was 1.
52g/61. The tap density was 1.759/-.

This was then calcined at 850°C for 2 hours.

The obtained powder is monoclinic zirconia, and the crystallite diameter determined by X-ray diffraction is approximately 25 OA, and the BIT specific surface area is approximately 1.
5m'/9, apparent bulk density is 1, v29/ct/1
．． The tap density was 2.06 g/-. Fine ittria powder with an average particle size of about (15 μm) was added to the zirconia fine powder thus obtained so that the amount of ittria was 3 mol %, and the powder was milled in a ball mill. The mixture was ground and mixed in ethanol for about 72 hours.
After drying for a period of time, a fine zirconia powder containing ittria was obtained.

This powder was compression molded using a mold press and a rubber press, and then baked in air at 1500°C for 2 hours.

The obtained sintered body mainly consists of a tetragonal system and has a density of 1.
,059/cd, and the bending strength was 108Ir9/-.

Example 2 Zirconium nitrate (ZrO(NOs), -2H,O)
427.69 was dissolved in 7117. Succinic acid (HOOOOOHR01% 0OOH) 1 &
400 d of an aqueous solution in which 79 was dissolved was added. The concentration of zirconium in this mixed aqueous solution is 1.0 mol/l, and the number of moles of succinic acid added is 10 mol of IIL per 1 mol of zirconium.

When this mixed aqueous solution was heated while stirring, approximately 70%
Milky-white colloidal particles began to form around ℃. Further heating was continued and the temperature was maintained at 98° C. for 48 hours to cause a reaction. After completion of the reaction, the produced sol was dehydrated under reduced pressure and heated to about 120 ml.
It was dried at ℃ for 24 hours.

The apparent bulk density of the obtained dry powder was 1. s69/cd.

The tap density was 1.7097 cd. This was then calcined at 900°C for 2 hours. The obtained zirconia fine powder is monoclinic, with an X-ray crystallite diameter of approximately 270X, Bl!
+T specific surface area is about 12-/l, and apparent bulk density is t
aa 9/aA-tap density was 1.9097 dl.

Fine ittria powder was added to the zirconia fine powder thus obtained so that the amount of ittria was 3 mol % in the same manner as in Example 1, and the mixture was ground in ethanol using a ball mill for 48 hours. This was then dried, molded in the same manner as in Example 1, and fired in air at 1500°C for 2 hours. The density of the obtained sintered body is &059/d, and the bending strength is 106K.
g/-.

Example 3 Zirconium oxychloride was dissolved in water to prepare an aqueous solution of zirconium salt having a zirconium concentration of 30t89/l as ZrO. This aqueous solution 7.351
! Ittria (YtOs purity 9λ9%) 125.69
800 rnl of an aqueous solution prepared by dissolving in hydrochloric acid was added.

Then water 5.65 / and Sierra acid (HOOO-000
H・2 Peng o) 45.49 aqueous solution 1.21
was added.

The concentration of zirconium in this mixed aqueous solution is 1.20 mol/l, which is 0.02 mol per 1 mol of hadzirconium in the added Sierra brew. This mixed aqueous solution was placed in a glass container, heated to about 100° C. with stirring, and reacted for 24 hours.

After the reaction was completed, the produced sol was dehydrated by heating under reduced pressure, and then dried at about 120° C. for 20 hours.

The apparent bulk density of the obtained dry powder was 1.289/cA.

The tap density was 1.759/-. Next, this dry powder was calcined at 850° C. for 2 hours. In this way, a zirconia-based fine powder containing 3 mol% of yttrium as YtOm was prepared. X-ray crystallite diameter is approximately 268A, BI
The T specific surface area is approximately 15t&/g, and the apparent bulk density of the powder is 1.769/7. The tap density was 20797 di.

This powder was ground in a ball mill for 72 hours in an ethanol solvent. The average secondary particle size of the fine powder obtained by drying P was about 0.5 μm. Next, this powder was compression molded using a mold press and a rubber press, and calcined in air at 1500° C. for 2 hours.

The obtained sintered body mainly consists of a tetragonal system, and as shown in Table 1, the sintered body density and bending strength are &079, respectively.
/- and 112 ky/s-.

Comparative Example 1 A zirconia-based fine powder containing 3 mol% of yttrium (Y40m) was prepared in the same manner as in Example 3, except that Scheler's acid was not added. In this case, heating and stirring were continued at approximately 100°C, but no colloidal particles were observed to form even after 72 hours had passed, and the solution remained transparent. For this reason,
The aqueous solution was directly heated, dehydrated, and concentrated to dryness.

As a result of XSt diffraction measurement of the obtained dry powder, the raw material zirconium oxychloride (Zr0O]4.8
4o] was found to be quite mixed.

Powder was prepared in the same manner as in Example 5, and a sintered body was produced. As shown in Table 1, the sintered body density was 5.9.
B9/64. The bending strength was 67 kg/-.

Examples 4-8. Comparative Examples 2 to 4 Zirconia fine powders containing 3 mol% of yttrium (ytos) were prepared in the same manner as in Example 3 by varying the amount of cisulic acid added. Furthermore, a sintered body was produced using the powder, and its density, bending strength, etc. were measured. The results are shown in Table 1.

Examples 4 to F in which the amount of citric acid added is α5 mol or less per 1 mol of zirconium! In this case, no specific X-ray diffraction peak was observed in the X-ray diffraction measurement of the dry powder. On the other hand, the amount of oxalic acid added is zirconium 1
In the case of Comparative Examples 2 to 4 where the amount exceeded [L5 mol per mole], a bulky white precipitate was formed simultaneously with the addition of citric acid. Furthermore, from the results of x11 diffraction measurement of the obtained dry powder, it was confirmed that zirconium sherate was produced.

As is clear from the results shown in Table 1, in order to obtain zirconia fine powder with excellent sinterability, the number of moles of polyhydric carboxylic acid such as silicic acid to be added must be increased per mole of zirconium. It is necessary that α5 mole or less. The amount of polycarboxylic acid added varies depending on the concentration of zirconium and other conditions, but the effect can be sufficiently obtained if the amount is about 0.01 mol or more per 1 mol of zirconium.

Examples 9 to 23 In the same manner as in Example 5, yttrium was replaced with Y by changing the type of polycarboxylic acid added to the aqueous solution of zirconium salt.
A zirconia-based fine powder containing 3 mol% of tO was prepared. Further, a sintered body was prepared using the powder, and the density 1 bending strength and other properties of the sintered body were measured. The results are shown in Table 2.

Example 24 An aqueous solution of zirconium oxychloride with a concentration of a8 mol/I and 1.2 mol/l of zirconium was prepared in the same manner as in Example 3 by coexisting α02 mol of fumarate ion per 1 mol of zirconium. did.

Pour this mixed aqueous solution into a glass container and stir for 10 minutes.
The mixture was heated to 0°C to react. A portion of the reaction solution was sampled at regular intervals, and the concentration of zirconium ions dissolved in the reaction solution was analyzed by chelate titration. From this value, the conversion rate of zirconium ions dissolved in the aqueous solution into insoluble colloidal particles (hereinafter referred to as hydrolysis rate) was determined. The results are shown in FIG.

Example 25 Zirconium oxychloride was dissolved in water to prepare an aqueous solution of zirconium salt having a zirconium concentration of 29549/:/ as ZrO12. This aqueous solution! t04/
Ittria (purity 91J) 8179 was heated and dissolved. To this solution was added 80 l of water and fumaric acid (HOO
Aqueous solution 21 in which 69.677 was dissolved was added.

The concentration of zirconium in this mixed aqueous solution is α8morph t
The number of moles of fumaric acid added is a,05 moles per mole of zirconium.

Pour this mixed aqueous solution into a glass container and stir for 90 minutes.
It was dried at ℃ for about 40 hours. After the reaction was completed, the produced sol was dehydrated by heating at 100° C. and concentrated until the liquid volume became about 51 ml. Next, n-pudanol (boiling point 118°C) 2
/ was added, and heating was continued for azeotropic dehydration. Thereafter, it was dried in a hot air dryer at 120° C. for about 24 hours.

The obtained dry powder was calcined at 850° C. for 2 hours to prepare a zirconia-based fine powder containing 3 mol% of yttrium as Yiaos. After that, it is crushed by a ball mill,
The obtained fine powder was compression molded and fired at 1500°C for 2 hours. The density of the sintered body thus obtained was 6.079.
7cd, bending strength is 1161e9/-.

Example 26 Zirconium oxychloride (ZrOO1@・8bird0]12
24.69 and magnesium chloride (Mgo 640)
407g dissolved in aqueous solution 2j, water 1.21 and ammonium oxalate t: (m 0. to H, 0) 27.
600 WLt of an aqueous solution in which 09 was dissolved was added. The concentration of zirconium in this mixed aqueous solution is 1.0 mol/1, and the number of mols of ammonium oxalate added is 0.05 mol per mol of zirconium.

This mixed aqueous solution was heated at about 98° C. for 20 hours to generate colloidal particles. Next, 500 d of n-octatool (boiling point: 195° C.) was added to this sol and heated for azeotropic dehydration. Further, this was dried in a hot air dryer at 100° C. for about 40 hours.

The obtained dry powder was calcined at 920°C for 2 hours.

Next, this was pulverized using a ball mill to obtain a zirconia-based fine powder containing 5 mol% of magnesium as MgO. The fine powder thus obtained was compression molded using a mold press and fired at 1540° C. for 2 hours. The density of the obtained sintered body was 5.769/ct/l.

The bending strength was 80:9/-.

Example 27 Dissolve zirconium oxychloride 11349 and cerium trichloride (OeO) 4.7%
) (7H(OH)OOOH) 26.49 d of an aqueous solution was added.

The concentration of zirconium in this mixed aqueous solution is 1.0 mol/
1, and the number of moles of tartaric acid added is 0.05 mole per mole of zirconium.

This mixed aqueous solution was heated at 98° C. for about 40 hours with stirring to generate colloidal particles. After the reaction is completed, the generated sol is further heated and dehydrated, and heated to approximately 24°C at 120°C under air circulation.
Dry for an hour.

The obtained dry powder was calcined at 850°C for 2 hours.

Next, this was ground with a ball mill to remove 0s of cerium.
A zirconia fine powder containing 12 mol% of O1 was obtained.

The fine powder thus obtained was compression molded using a mold press and fired at 1500° C. for 2 hours. The obtained sintered body mainly consists of tetragonal system and has a density of 6.159/ff.
The bending strength was 87 to/-.

Example 28 Zirconium oxychloride (ZrOO34@8H,O)
605.8, yttrium trichloride (YOI3.64o
) 24.59 and aluminum trichloride 1, nium (A101
3.61 (!O) Aqueous solution 31 in which 64.59 was dissolved
! 760m7 of an aqueous solution containing 257g of oxalic acid (HOOO・0OOH@2H,O) dissolved in it! was added. The concentration of zirconium in this mixed aqueous solution is 0.5 mol/l, and the number of moles of sinioic acid added is 0.10 mol per 1 mol of zirconium.

This mixed aqueous solution was heated at about 100° C. for 24 hours to generate colloidal particles. This was then dried in a hot air dryer for 10 minutes.
It was dried at 0°C for about 24 hours.

The obtained dry powder was calcined at 900°C for 2 hours.

Next, this was ground with a ball mill to contain 4 mol% of yttrium as YA and aluminum as Alt.
A zirconia-based fine powder containing 5% by weight of Os was prepared.

The thus obtained zirconia-based fine powder was compression molded using a mold press and a rubber press, and fired at 1400° C. for 3 hours. The obtained sintered body mainly consists of tetragonal and cubic systems, has a density of 5.9 (1/i, and a bending strength of 1
It was 07kg7vd.

Comparative Example 5 A mixed aqueous solution was prepared in the same manner as in Example 25, in which the concentration of zirconium was (L8 mol/l) and 120 mol of acetic acid was added to 1 mol of zirconium instead of fumaric acid.

This mixed aqueous solution was heated at about 100° C. for 72 hours while stirring. However, no formation of colloidal particles was observed and the solution remained transparent.

Comparative Example 6 An aqueous solution of a zirconium salt was heated in the same manner as in Comparative Example 5 except that α1 mol of propionic acid was added per 1 mol of zirconium instead of vinegar. However, no colloidal particles were observed to form, and the solution remained transparent even after 72 hours.

[Brief explanation of the drawing]

FIG. 1 shows the results of the heated hydrolysis reaction according to the method of the present invention.
FIG. 3 is a diagram showing the relationship between reaction time and hydrolysis rate. Patent applicant: Toyo Soda Kogyo Co., Ltd. Figure 1 Reaction time (Hr)

Claims (2)

[Claims] (1) Polyvalent carboxyl having 2 or more and 4 or more carboxyl groups in one molecule in an aqueous solution containing a water-soluble zirconium salt alone or a water-soluble zirconium salt and magnesium, calcium, or an element with a valence of 3 or more. A method for producing zirconia-based fine powder, which comprises adding 15 moles or less of an acid or a salt thereof to 1 mole of zirconium, heating and hydrolyzing the mixture to produce colloidal particles. (2) The zirconium concentration of the water-soluble zirconium salt aqueous solution is LL1 mol/1 or more, Claim No. 1
) The method for producing the zirconia-based fine powder described in item 2.