JPS63274625A - Production of fine zirconia powder having uniform particle size to be used as material for sintering - Google Patents

Abstract

PURPOSE:To produce the title fine powder contg. scarcely agglomerated particles by heating crystalline hydrous zirconyl chloride or a solid mixture consisting primarily thereof at a specified temp. in a closed vessel, holding the product at the temp., then heating, dehydrating, caking, drying or calcining after releasing the product from tightly closed condition. CONSTITUTION:Crystalline hydrous zirconyl chloride alone, or a solid mixture consisting primarily of the crystalline hydrous zirconyl chloride contg. also <=0.2 (by molar ratio basing on Zr) one kind of metal salt or metal hydroxide which can be dissolved in ZrO2 as solid soln. and forming metal oxide, is used. The material is heated at 150-300 deg.C in a closed vessel, and held for a sufficient time necessary for generating crystallized ZrO2. In this stage, said zirconyl chloride is hydrolyzed slowly by its own water of crystallization to form white paste mixture. Then, the vessel is released from tightly closed condition, and the product is dehydrated by heating as it is, and dried or calcined. By this method, relatively coarse fine particles having >=0.3mu particle size of relatively uniform particle size distribution are obtd.

Description

[Detailed description of the invention] The invention is highly efficient and economical, suitable for industrial production.

The present invention relates to a method for producing sized zirconia fine powder for sintered bodies.

The raw material powder used for sintering in general, especially for sintering oxides, is used to achieve densification at relatively low temperatures.

Each powder particle has high purity, fine particles, uniform particle size and spherical shape.

It is also desired that there is no solid aggregation between the powder particles. However, if the particles are too fine, the sintering activity increases, but on the other hand, strong agglomeration between particles tends to occur, and disadvantages such as the inability to increase compaction density increase. According to experiments conducted by the present inventors, monoclinic zirconia fine powder used for sintered bodies such as zirconia ceramics and zirconia dispersion-strengthened ceramics and Y, 0
．． In the case of square or cubic zirconia fine powder in which Q,
Fine particle powder with a relatively coarse uniform particle size of about 371 m or more is suitable. However, the current industrial manufacturing method of zirconia fine powder for sintered bodies uses monoclinic zirconia fine powder, tetragonal to cubic zirconia fine powder stabilized with Y20a, CaO, MgO, etc., and zirconium hydroxide. This is due to the calcination of hydroxide or co-precipitated hydroxide, or the calcination of hydrolysis products of zirconium compounds or co-precipitates with them.For those made from hydroxide, the particles become coarse and irregular.
In addition, the hydrolysis products are extremely fine particles, and local sintering and strong agglomeration occur during calcination, both of which result in irregularly shaped 2
Particle size molecule: 5 (7) The zirconia powder was wide, and was not necessarily satisfactory for use in sintered bodies.

The present invention does not have these drawbacks and has a relatively uniform particle size distribution. Relatively coarse particles of about 0.3 μm or more can be produced. The present invention provides a new method for producing sized fine zirconia powder for sintered bodies, which comprises extremely economical improved thermal hydrolysis and subsequent treatment. The inventor is
Crystalline hydrated zirconyl chloride is directly heated to 150~
It was discovered for the first time that when heated to a temperature of 300°C and held for a long time, it gradually hydrolyzed by its own water of crystallization, forming a white paste-like mixture. When this paste-like mixture is dispersed in water and observed under an electron microscope, it shows that
It is composed of extremely fine ultrafine particles of about 0° 1 m or less, and when examined with X-rays when dried, it is a monoclinic zirconia ultrafine crystal. However, the present inventor further discovered that after the paste mixture was produced, it was directly heated, dehydrated, and solidified without being cooled to room temperature without being unsealed, and then observed with a scanning electron microscope. It is noteworthy that f:oI was found to form relatively coarse and relatively uniform spherical agglomerated particles.

Once sufficiently dried, even if water or an acid such as hydrochloric acid is added again to create a suspension, these spherical aggregated particles will no longer be 0.
．． It was found that ultrafine particles of about 0.01 μm or less were dispersed and kept in a single spherical agglomerated shape. The present invention is based on these discoveries.

Therefore, the first feature of the method of the present invention is that crystalline hydrated zirconyl chloride is directly heat-treated at a temperature of 150 to 300''C in a closed container, and also before the zirconia crystals are formed and subjected to a The second feature is that it is heated, dehydrated, assimilated and dried as it is.In other words, the present invention provides crystalline hydrated zirconyl chloride or crystalline hydrated zirconia chloride fine powder which can be solid-dissolved in Z'02. A solid mixture containing one or more types of metal oxides such as Kinbo salt or hydroxide in a molar ratio of 0.2 or less to zirconium is heated in a closed container to a temperature of 150 to 300°C to form zirconia. Hold for sufficient time for crystallization to form.

Next, the container was unsealed and the product was heated and dehydrated.
A method characterized by drying or calcining.

In addition, crystalline hydrous zirconyl chloride alone and a solid mixture containing one or more metal chlorides or hydroxides soluble therein are heated to a temperature of 150 to 300°C in a closed container to form zirconia crystals. 1. Next, the container is unsealed, and the product is heated and dehydrated as it is. Once sufficiently solidified and dried, water or acid is added again to make it into a suspended state, and soluble components are removed and additional components are removed. A relatively uniform particle size distribution of 8 was achieved by a method characterized by adjusting the chemical composition, such as adding coprecipitation, and then calcining at a temperature of 600° C. or higher. This makes it possible to obtain relatively coarse particles of about 0.3 pm or more.

The method of the present invention is characterized in that the crystalline hydrous zirconyl chloride is directly heat-treated in a closed container, but the presence of mixed water and a small amount of free water is allowed at a molar ratio of up to 5 to zirconia. In addition, crystallization water of hydrated salt as an additive is not only acceptable.

In some cases, high temperatures may be preferable since they aid in hydrolysis and low temperatures may fix water; in other cases, the aggregate particle size may be somewhat smaller. Therefore, the soluble metal chlorides or hydroxides used as additives in the present invention are useful for both particle size control and process stabilization. However, it is desirable to use a substance that does not cause any harm even if it remains in the final sintered body.

The metal ion used in this sense is Ca''.

Mg2+1. A11+ etc. are suitable. The relatively coarse agglomerated fine particles produced by direct heat treatment in a closed container according to the present invention have a spherical shape, and even when calcined at a relatively high temperature of 1000°C or higher, the particles do not sinter inside the agglomerated particles. Although it is densified, strong agglomeration due to sintering between the aggregated particles is difficult to occur (the particle size is relatively uniform. This results in a fine zirconia powder with a uniform particle size for excellent sintered bodies).

In the method of the present invention, it is extremely important to first dehydrate and solidify and dry the paste-like mixture obtained by thermal hydrolysis. If even a small amount of water is added to this paste-like mixture first, or if it is cooled to room temperature and left to stand for a long time before being heated and solidified, the agglomerated particles may be broken or irregularly coarsened. Even if water or hydrochloric acid is added again to form a suspension, the suspended particles will not be uniformly aggregated. However, if a sufficient amount of a strong electrolyte such as calcium chloride coexists during hydrolysis, with a molar ratio of at least 0.5 or more to zirconium, water may be taken as crystal water during cooling, or ionized ions may coordinate water. Perhaps because it prevents the dispersion of the zirconia ultrafine crystals, relatively coarse, uniform agglomerated particles remain even after cooling to room temperature, and are stabilized by heating, dehydration, solidification, and drying. A suspension of aggregated fine particles can be obtained. However, before adding water or hydrochloric acid to the hydrolyzed product to form a suspension, it is an essential condition for the present invention that the product be sufficiently heated to dehydrate and solidify and dry. Further, in the present invention, although the effect of chlorine ions is not necessarily clear, chlorine ions are necessary for thermal hydrolysis and particle coarsening.

The soluble metal chloride appears to be useful in stabilizing relatively coarse, uniformly aggregated particles.

The method of the invention is as evidenced by one or more of the following.

Since the crystalline hydrous zirconyl chloride is heat-treated directly in a sealed container, the work is extremely simple, and most of the treatment is carried out efficiently in the most concentrated zirconium-containing state, and the process is relatively uniform through a simple process. Agglomeration and coarsening: This makes it possible to obtain zirconia fine powder particles suitable for sintered bodies, and is not only used in the industrial production of fine powders for zirconia ceramics or zirconia dispersion-strengthened ceramics.

It is also extremely valuable for industrial production of high-performance ceramics.

Example 1 Reagent zirconyl chloride (ZrOCl2.8H2o) approx. 25
1 wo.

Place it in a stainless steel container as it is: Place it in a Teflon container, seal the whole thing, heat it in a thermostat kept at 200″C, and keep it for 5 days. Immediately, it was placed in a drying mold at 150°C to dry and solidify.This was ground in a mortar.

Distilled water was added to extract the soluble components, followed by repeated centrifugation, washing with water, and drying to form a powder. According to X-ray diffraction, this powder consists of diagonal zirconia with an apparent crystallite size of about 50 particles, but scanning electron microscopy shows that each powder particle has a relatively uniform diameter of about 1 μm. The particles were agglomerated.

Example 2 Reagent zirconyl chloride (ZrOC1□-8H20) approx. 23
9 and.

Weigh out about 0.8y of calcium chloride (CaC1.6H20), mix it, put it directly into a Teflon container placed inside a stainless steel container, seal the whole thing, and place it in a constant temperature chamber kept at 200°. The white paste-like material produced was heated and held for 55 days for hydrothermal treatment.
It was placed in a drying mold at 50°C and dried and solidified. After pulverizing this in a mortar and calcining it at 900°C, it is easily loosened into a powder, and this powder is made of square zirconia with about 5 mo1% of CaO dissolved in it.

According to a scanning electron microscope, the diameter is relatively uniform, approximately 0.5 μm.
It consisted of fine particles.

Example 3 Reagent zirconyl chloride (ZrOCl2-8H20) approx. 25
Da.

Place the container as it is in a Teflon container that has been stored in a stainless steel container for a month, seal the whole thing, heat it in a thermostat kept at 200℃, keep it for 5 days, and immediately remove the white paste-like material that is formed. It was placed in a drying mold at 150'C to dry and solidify. Grind this in a mortar.

Add distilled water to extract soluble components, repeat centrifugation and wash with water, add about 0.9 y of yttrium chloride, coprecipitate as yttrium hydroxide with aqueous ammonia, dry this coprecipitate and ``(:) The calcined material is easily loosened and becomes a powder, and this powder is approximately
According to a scanning electron microscope, it consisted of relatively uniform spherical fine particles with a diameter of about 0.5 μm.

Example 4 Reagent zirconyl chloride (ZrOCl2.8H20) 13
9 and.

Reagent Magnesium chloride (MgC+2・6H20) 1
3 (Put the J (J) mixture directly into a stainless steel container: Place it into a Teflon container and seal the whole thing, 20
Heat it in a thermostat kept at 0''C and keep it there for 5 days.

The resulting white paste was immediately put into a drying mold at 150°C and dried and solidified. This was ground in a mortar, distilled water was added to dissolve the soluble components, centrifuged repeatedly, washed with water, and dried to form a powder.

This powder has an apparent crystallite size of about 40 monoclinic zirconia, but according to a scanning electron microscope, it consists of relatively uniform spherical fine particles with a diameter of about 0.67 zm. In addition, approximately 0.461 ythtrium chloride was added to this water @ suspension before drying to dissolve it, and ammonia water was added to this to coprecipitate zirconia and yttrium hydroxide. After drying the coprecipitate, 100%
The powder calcined at 0°C and lightly ground is approximately 3 mol','o
According to a scanning electron microscope, it consists of relatively uniform spherical fine particles with a diameter of about 0.2 to 0.3 μm.

Claims (2)

[Claims] (1) Crystalline hydrated zirconyl chloride alone, or crystalline hydrated zirconyl chloride as the main component, and one or more metal salts or hydroxides that form metal oxides that can be dissolved in ZrO_2 in a molar ratio of 0 to zirconium. A solid mixture containing a ratio of .2 or less is heated to a temperature of 150 to 300 °C in a closed container and held for a sufficient time to generate and crystallize zirconia, and then the container is unsealed and the product is heated and dehydrated as it is. A method for producing a sized zirconia fine powder for a sintered body, which comprises drying or calcining the zirconia powder. (2) Zirconia is produced by heating crystalline hydrous zirconyl chloride alone or a solid mixture containing one or more metal chlorides or hydroxides soluble therein to a temperature of 150 to 300°C in a closed container. Hold for a sufficient time to crystallize, then unseal the container and heat and dehydrate the product as it is. Once sufficiently solidified and dried, water or acid is added again to make it into a suspended state, and soluble components are removed or added. A method for producing a sized zirconia fine powder for use in a sintered body, which comprises adjusting the chemical composition by adding and co-precipitating components, and then calcining it to a temperature of 600°C or higher.