JPH0337151A - Production of ceramic fine powder - Google Patents

Abstract

PURPOSE:To easily and economically produce ceramic fine powder giving a formed article having high strength by gelatinizing a synthetic slurry or sol of a ceramic compound with a gelling agent and heat treating the gel block to eliminate water and the gelling agent from the gel. CONSTITUTION:A synthetic slurry or sol of a ceramic compound is prepared beforehand. The ceramic compound is preferably calcium phosphate compound, titania, magnesia, alumina. zirconia, etc. The synthetic slurry or sol is gelatinized with a gelling agent (e.g. pectin or sodium alginate). Ceramic powder composed of extremely fine particles can be produced by heat-treating the obtained gel block, thereby evaporating the water and decomposing the gelling agent. The powder can be formed into a formed article having high strength and density and suitable as a bio-material, optical material, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application The present invention relates to a method for producing fine ceramic powder useful for fine ceramics.

"Prior art and its problems" Fine ceramics used for various biomaterials, optical materials, electronic materials, structural materials, etc. are made into fine powders with high purity in order to improve strength, density, and various functions. ization is required.

Dry and wet synthesis methods are conventionally known for producing ceramic powders. To produce calcium phosphate compounds by a wet method, a method in which a calcium compound and a phosphoric acid compound are reacted in water is generally adopted.

When obtaining powder, especially fine powder, as a raw material for ceramics by filtration, centrifugation, etc. from the slurry obtained by this wet method, a pulverization step using a ball mill, jet mill, etc. is required in addition to the drying step. . However, in this case, impurities may be mixed in due to wear of the equipment, and calcination may be required. When a slurry is pulverized by spray drying, it can be pulverized into particles having a particle size of about 5 μm at most. When performing dry molding,
A ceramic molded body having sufficient strength can be obtained with the aggregated particles obtained by spray drying, but when performing wet molding, the strength will be insufficient unless finer particles are used. Furthermore, when freeze-drying is used, although a fine powder can be obtained, a calcination step cannot be performed at the same time. Furthermore, freeze-drying requires the use of expensive equipment and has the problem of not being able to be manufactured at low cost.

``Purpose of the Invention'' The present invention is directed to the production of a powder consisting of extremely fine ceramic compound particles suitable for wet molding from a slurry obtained by a wet synthesis method at low cost, and to which a calcination or firing process can be performed simultaneously. The purpose of the present invention is to provide a method for producing powder.

"Structure of the Invention" The method for producing ceramic fine powder of the present invention includes gelling a synthetic slurry or sol of a ceramic compound by adding a gelling agent, and heat-treating the resulting gel mass to remove water and the gelling agent. It is characterized by

In the present invention, examples of the ceramic compound include calcium phosphate compounds, titania, magnesia, alumina, and zirconia. These compounds are used in the method of the present invention as a slurry or sol obtained by a wet synthesis method, respectively.

As the gelling agent, agar, pectin, carrageenan, sodium alginate, gellan gum, etc. can be used. The gelling agent only needs to be able to maintain a state in which the ceramic compound is uniformly dispersed in the slurry, and since it is ultimately removed by thermal decomposition, it is preferable to use the gelling agent in the minimum necessary amount.

Next, the present invention will be explained regarding a method for producing a calcium phosphate compound.

Examples of calcium phosphate compounds include apatite such as hydroxyapatite, tricalcium phosphate, and the like. These calcium phosphate compounds are produced by a wet synthesis method as follows. First, hydroxyapatite is obtained by reacting phosphoric acid and calcium hydroxide in water such that the atomic ratio of Ca/P is 1.67. In addition, tricalcium phosphate is C
It is obtained by reacting phosphoric acid and calcium hydroxide so that the a/P atomic ratio is 1.50, and α-tricalcium phosphate or β-tricalcium phosphate can be obtained depending on the firing temperature.

In the method of the present invention, a slurry of calcium phosphate compounds obtained in the wet synthesis process as described above is gelled by adding a gelling agent.

In this way, since the calcium phosphate compound produced by the wet method is made into a gel as it is, the gel is interposed between the generated compound particles, drying and calcining are performed in this state, and the firing process is continued. You can also do that. As described above, by dispersing the compound particles in the gel and subjecting them to heat treatment, the aggregation of the compound particles occurs only after the gel has disappeared, so that extremely fine particles can be obtained. moreover,
Since the particles are extremely fine, firing can be performed at a relatively low temperature, particle growth due to firing is significantly reduced, and extremely fine calcium phosphate ceramic powder can be obtained.

On the other hand, wet synthesis methods for zirconia include a method in which a zirconium salt aqueous solution is made alkaline to produce zirconium hydroxide or zirconia hydrate, and this is heated to remove moisture, and a zirconia sol produced by hydrolysis of an alkoxide is heated. There are ways to disassemble it.

Further, titania, magnesia, and algos are wet-processed, or in the same manner as zirconia.

In order to produce oxide-based ceramics such as zirconia, titania, magnesia, or alyos by the method of the present invention, the hydroxide (
Alternatively, a slurry or sol of oxide hydrate may be gelled with a gelling agent and then heat treated. In this case, the heat treatment is carried out at a temperature at which the gelling agent used is decomposed and removed and water is removed to obtain the above-mentioned fine oxide powder. The atmosphere for the heat treatment may be air, inert gas, or under reduced pressure. A firing step can also be performed following this heat treatment step.

According to the method of the present invention, the diameter is 5 μm or less, usually 0.1 to 0.
Since fine ceramic powder having a particle size of 5 μm is obtained, a molded body with improved strength and density can be produced by wet molding.

Note that the fine particles obtained in the present invention are not suitable for dry molding as they are because of their amorphous shape, but by making them into granules by any granulation method, they can be dry molded like particles obtained by spray drying. It can also be made suitable for

"Examples of the Invention" Next, the present invention will be described in more detail based on Examples, but the present invention is not limited thereto.

Example 1 Calcium hydroxide and phosphoric acid were reacted in water by a known wet method to obtain a 2% slurry of hydroxyapatite. Next, gellan gum (Kelc).

Manufactured by Division of Merck & Co.
After adding 8 g of Kelcogel (trade name) to 200 g of water, it was heated in a microwave oven to dissolve it. Then, 300g of pre-heated slurry and gellan gum solution were mixed and stirred,
Cooled in a water bath to obtain a gel. When this gel was heat-treated at 500°C, fine hydroxyapatite powder with a particle size of 0.2 to 1 μm was obtained.

Example 2 Zirconium butoxide (manufactured by Nippon Soda, trade name TBZ)
'R) Ig with 0.01g of calcium nitrate dissolved in water 1
When added to 00d, it became cloudy and a slurry was formed.

Next, carrageenan (Mer.

After adding 8 g of Satyagel NP5B (manufactured by Rousselot 5atia, trade name) to 200 g of water, it was heated in a microwave oven to dissolve it. Then, the preheated slurry 100ad and the carrageenan solution were mixed, stirred, and cooled in a water bath to obtain a gel. This gel was heat-treated at 500°C to obtain a fine powder with a particle size of about 2 μm.

Example 3 Titanium butoxide (manufactured by Nippon Soda, trade name B-1)
When Ig was added to 100 d of water, it became cloudy and a slurry was formed.

Manufactured by Division of Merck & Co.
After adding 8 g of the product (trade name: Kelcogel) to 200 g of water, it was heated in a microwave oven to dissolve it. Then, preheated slurry 100I11 and gellan gum solution were mixed, stirred, and cooled in a water bath to obtain a gel. This gel was heated to 500°
When heat treated with C, a fine powder with a particle size of about 2 μm was obtained.

"Effects of the Invention" According to the present invention, fine ceramic powder can be produced at low cost with extremely simple operations.According to the present invention, a slurry or sol of a compound produced by a wet method is directly converted into a gel. Therefore, gel is present between the generated compound particles, and drying and calcination are performed in this state, and the calcination process can be continued. As described above, by dispersing the compound particles in the gel and subjecting them to heat treatment, the aggregation of the compound particles occurs only after the gel has disappeared, so that extremely fine particles can be obtained. Furthermore, since the particles are extremely fine, firing can be performed at a relatively low temperature, grain growth due to firing is significantly reduced, and extremely fine ceramic powder can be obtained.

Therefore, according to the method of the present invention, a fine ceramic powder useful for fine ceramics can be obtained, and products with high strength and density can be produced by molding this fine powder by wet molding or by dry molding after granulation. can be manufactured.

Claims (3)

[Claims] 1. A method for producing fine ceramic powder, which comprises gelling a synthetic slurry or sol of a ceramic compound by adding a gelling agent, and heat-treating the resulting gel mass to remove water and the gelling agent. 2. The ceramic compound is a calcium phosphate compound,
2. The method for producing a fine ceramic powder according to claim 1, wherein the ceramic powder is titania, magnesia, alumina or zirconia. 3. 2. The method for producing fine ceramic powder according to claim 1, wherein the gelling agent is selected from the group consisting of agar, pectin, carrageenan, sodium alginate, gellan gum, and the like.