JPS6221750A - Manufacture of ceramic sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing a high-density ceramic sintered body. More specifically, the present invention relates to a method for manufacturing a ceramic sintered body characterized by using zirconia-based ultrafine particles as a sintering aid when manufacturing a high-density ceramic sintered body.

[Conventional technology]

In recent years, research and development on ceramics such as alumina, zirconia, silicon carbide, and silicon nitride has been progressing, and their excellent thermal, mechanical, and chemical properties are making their applications in many fields a reality.

These ceramics must be molded and sintered at high temperatures in order to exhibit their functions, and various techniques have been developed for this purpose.

Methods for producing ceramic sintered bodies include pot press method (HP), hot isostatic pressure sintering method (HIP), and pressureless sintering method, but pressureless sintering method is more likely to produce products with complex shapes. is attracting attention.

However, in the pressureless sintering method, it is difficult to select the firing conditions; for example, if the firing temperature is low, the result is a low-grade sintered body and no strength is obtained, and if the firing temperature is high, a high-density product is obtained. However, depending on the ceramic raw material, volatile components may be scattered from the surface of the sintered body during firing, resulting in variations in strength.

To deal with these problems, for example, it has been proposed to add boron or boron compounds, aluminum or aluminum compounds, and carbon to these as sintering aids for silicon carbide, which is said to be difficult to sinter. Among silicon nitrides that are difficult to sinter, itria (Y2
O2), 7-'/screw 7 (MQO), 7) tt Mina (Al120a), Beryllia (Bed), Calcia (Cab), Alumina-Magnesia (MOAi203)
) It has been proposed to add irradiation to cause sintering.

However, even if sintered bodies are produced by adding these sintering aids, the current situation is that both strength and density are still insufficient.

(Object of the invention) The present invention solves the problems of the above-mentioned conventional technology and provides a method for obtaining a high-density and high-strength ceramic sintered body. We propose to use .

[Means and effects]

That is, the present invention is specified as follows.

(1) When producing a ceramic sintered body, an average particle size of 0.1 is added to the ceramic raw material as a sintering aid.
A method for producing a ceramic sintered body, which comprises adding and mixing ultrafine zirconia particles of micron or less, particularly 0.05 micron or less, shaping and sintering.

(2) Zirconia-based ultrafine particles as a sintering aid contain at least one oxide selected from the group consisting of ittria, magnesia, and calcia as a stabilizer in an amount of 1 to 20 mol % based on zirconia (ZrO2). The method according to (1) above, characterized in that the method comprises:

The present invention will be explained in more detail below.

Ceramic raw materials used in the present invention include:
Any of oxides such as alumina, titania, and zirconia and non-oxides such as silicon carbide, silicon nitride, boron nitride, and titanium nitride can be used, and in particular silicon carbide and silicon nitride, which are difficult to sinter, are selected as materials.

These raw materials are used in the usual powder form, that is, with a particle size of 0.1 to 10 microns.

The sintering aid specified by the present invention needs to be finer than the average particle diameter of the ceramic raw material to be sintered.

The sintering aid used is uniformly mixed in an amount of 30 times or less, particularly 10% by weight or less, based on the ceramic raw material. The zirconia-based ultrafine particles specified above can be prepared by any method, but
Advantageously, particles prepared by the following method can be obtained with uniform particle size and exhibit excellent effects.

That is, when aqueous ammonia is added to an aqueous solution of a zirconium salt or a mixed solution containing a zirconium salt and at least one metal selected from yttrium, calcium, and magnesium to form a precipitate, the precipitate formation reaction is performed using a flow reaction method. This is a method in which the PI-1 during reaction is continuously maintained at a constant pH within the range of 6713 to form a precipitate, and the resulting precipitate is separated, dried, and calcined.

Further, the zirconia-based ultrafine particles used in the present invention are preferably stabilized with at least one of itria, magnesia, and calcia as a stabilizer, and have a concentration of 1 to 20% relative to zirconia (ZrO2).
A mole % range of about 10% gives preferable results.

As the molding method used in the present invention, commonly used methods such as a press method, a slurry casting method, an extrusion molding method or an injection molding method are appropriately employed.

The ceramic raw material powder and the sintering aid are wet-mixed by a common method such as a ball milling method.Depending on the molding method, an organic gasifier, a binder, an antifoaming agent, etc. may be added.

Since the thus obtained compact has a fine sintering aid of 0.1 micron or less added, the sintering temperature is also lowered by 100 to 150°C compared to the conventional case of using a large aid of zero particle size. The advantages have been fully realized, and the sintered density is also the theoretical value of 9.
It has been confirmed that the percentage is 5% or more.

Examples are given below to specifically demonstrate the effects of the present invention.

- [Preparation of sintering aid Δ] A mixed aqueous solution of yttrium chloride and zirconium oxychloride was prepared so as to contain 8 mol% of Y203. The liquid concentration was 0.2 mol/i of ZrO+. 300 d of water was placed in a seed reactor equipped with a stirrer, and aqueous ammonia was added to adjust the pH to 9.0. Add the above mixed aqueous solution to this. At a wave speed of 50 m/min, ammonia water (10% by weight aqueous solution) was added every minute! The mixture was injected with stirring using a constant temperature pump. The neutralization coprecipitation reaction was carried out continuously while carrying out the reaction liquid with another metering pump so that the liquid ω in the reactor remained constant. A neutralization coprecipitation reaction was carried out while finely adjusting the flow rate of ammonia water so that the pH during the reaction was 9±0.2. Hydroxide in the discharged liquid was separated from the mother liquor by filtration, and then ammonium chloride was removed by washing with water.

The obtained hydroxide was dispersed in n-butanol and dehydrated by distillation at atmospheric pressure until the solution temperature reached 105°C. After drying at 60°C under reduced pressure,
It was baked at 0°C for 1 hour. The resulting powder 120Q and toluene 750d were placed in a No. 21 ball mill and ground for 6 hours, followed by drying to obtain a fine powder with weak secondary agglomeration. The specific surface area of the obtained powder is 96/Q,
The average particle size was o, oi microns.

[Preparation of Sintering Aid B] A mixed aqueous solution of yttrium chloride and zirconium oxychloride was prepared so as to contain 3 mol % of Y203. The liquid concentration was 0.2 mol/i as ZrO2.

300 ml of water was placed in a seed reactor equipped with a stirrer, and aqueous ammonia was added to adjust the pH to 8.5. To this was added the above mixed aqueous solution at a wave speed of 50 d/min, and ammonia water (28
wt% aqueous solution) was added at a rate of 50% per hour with stirring using a metering pump. The neutralization coprecipitation reaction was carried out continuously while the reaction liquid was carried out using another constant temperature pump so that the liquid volume/J- in the reactor remained approximately constant. A neutralization coprecipitation reaction was carried out while finely adjusting the flow rates of the mixed aqueous solution and ammonia water so that P l-1 was 8.5±0.2 during the reaction.

The hydroxide in the discharged liquid was separated from the mother liquor by filtration, and then ammonium chloride was removed by washing with water.

The obtained hydroxide is dispersed in n-butanol, dehydrated by distillation under atmospheric pressure until the solution temperature reaches 105°C, and then the n-butanol dispersion containing the dehydrated oxide is spray-dried. A powder with good fluidity was obtained. By calcining this powder at 850° C. for 1 hour, a fine zirconia powder containing 3 mol % of itria without any agglomerates was obtained. The average particle diameter of this fine powder was 0603 um, 80% or more of which was 0.02 to 0.04 um, and the specific surface area was 47 Td/C1.

Example 1 1II! To silicon nitride powder having a weight of 98% by weight and an average particle size of 0.8 μm, 5% by weight of the stabilized zirconia as the sintering aid A obtained above, 2% by weight of polyvinyl alcohol, and a small amount of water were added. Mixing was carried out at 10 o'clock in an alumina ball mill.

The slurry thus obtained was granulated using a spray dryer, and then formed into rubber presses at a pressure of 1.000 Kg/cIi to form granules with a diameter of 101rIIRφ and a length of 50III.
I! A rod-shaped molded article I was obtained.

When this molded body was fired at 1.650° C. for 4 hours in a nitrogen stream, a sintered body with a theoretical density of 97% was obtained.

Comparative Example 1 The following molded body was obtained in the same manner as in Example 1 except that fine powder stabilized zirconia and C having an average particle diameter of 0.5 μm were used and the firing temperature was changed.

Firing temperature Theoretical density 1, 600°C 91% 1, 750°C 95% Example 2 Partially stabilized zirconia (Y203) with an average particle size of 0.5 μm
To the powder (containing 3 mol%), 5% of the partially stabilized zirconia of the sintering aid B obtained above, 1% of polyvinyl alcohol (iffi%), and a small amount of water were added, and the mixture was heated in an alumina ball mill at 10 o'clock. Timed mixing was performed.

The slurry thus obtained was molded in the same manner as in Example 1 and fired at 1,400°C for 2 hours in a stream of air, yielding a fired body with a theoretical density of 99.5%. .

For comparison, when the same operation was performed and fired without adding the partially stabilized zirconia fine powder of sintering aid B obtained above, only a sintered body with a theoretical density of 90% was obtained.

Claims (2)

[Claims] (1) When producing a ceramic sintered body, ultrafine zirconia particles with an average particle size of 0.1 micron or less are added and mixed as a sintering aid to the ceramic raw material, and the mixture is shaped and sintered. A method for manufacturing a ceramic sintered body. (2) Zirconia-based ultrafine particles as a sintering aid contain at least one oxide selected from the group consisting of yttria, magnesia, and calcia as a stabilizer in an amount of 1 to 20 mol% based on zirconia (ZrO_2). The method according to claim (1), characterized in that the method includes the following range.