JPH07167771A - Dispersing method for ceramic powder - Google Patents

Abstract

PURPOSE:To safely and surely disperse ceramic powder scarcely using dispersant by using as dispersing medium one of super pure water with electric resistance over a specific value or a degased water with dissolved oxigen below a specific value and electric resistance over a specific value. CONSTITUTION:Either of super pure water with electric resistance over 170MOMEGA or degased water with dissolved oxigen concentration below 10ppm and electric resistance over 1MOMEGA is used as a dispersing medium. The ceramic powder to be dispersed is not limited to a specific material if only it does not elude metal ion when dispersed in water. For example, such non-oxide ceramics as siliconcarbide, siliconnitride, etc., are preferable. The super pure water has little conductive material ion, and therefore has high electric resistance and small surface tension. Thus, the material causing aggregation and gas molecules adsorbed on powder surface are ioninzed, wettability of the powder is improved and stable dispersion is realized. Also, for the specific degased water, similar effect to the super pure water is expected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dispersing a ceramic powder, particularly a fine powder which easily agglomerates.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the heat resistance and hardness of ceramics, and they have been used in various fields. Conventional ceramics are different from metals in that they have a manufacturing method in which ceramic powders are baked and solidified.
It was necessary to accurately measure the particle size of the ceramic powder.
Conventionally, as a method of dispersing the ceramic powder, a method of dispersing the ceramic powder in water (distilled water or ion-exchanged water) or an organic solvent as a dispersion medium has been generally used. Further, if necessary, a dispersant is added or dispersed in the primary particles with an ultrasonic dispersing device or a ball mill.

[0003]

Water is a generally used dispersion medium without the need to take into consideration problems such as pH, but when ceramic powder is dispersed, the surface tension is large and the powder agglomerates. However, it was difficult to measure the particle size distribution accurately as it is. Therefore, it is common practice to add a large amount of a dispersant and to disperse the dispersant using a disperser.

The use of the dispersant can prevent the powder from agglomerating and effectively disperse the powder, but the dispersant is different from the original particle size because it adheres to the primary particles. In addition, since gas molecules are generally adsorbed on the surface of the particles, the particles were unstable even after the dispersion treatment, for example, the particles started to aggregate again. On the other hand, when an organic solvent is used as the dispersant, it is effective in dispersing the particles, but there is a problem in workability in terms of handling, such as being volatile or toxic.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a dispersion method which is simple, safe, and capable of measuring an accurate particle size distribution of a ceramic powder with respect to these problems. That is, in the method of dispersing ceramic powder, the ultrapure water having an electric resistance of 17 MΩ or more, or the dissolved oxygen concentration in water of 10 ppm or less and the electric resistance of 1 MΩ.
Any of the above degassed water is used as a dispersion medium. Here, the ceramic powder is not particularly limited as long as it is a material that does not elute metal ions or the like when dispersed in water, but is particularly effective for non-oxide ceramics such as silicon carbide and silicon nitride.

[0006]

In general, ultrapure water can be obtained by passing some purified water (distilled water, ion-exchanged water, etc.) through an ion exchange resin, which has been developed especially for ultrapure water. . Since ultrapure water has very few conductive ions, it has a high electrical resistance (generally 17M
It has the characteristic that the surface tension is small. Therefore, the substance that causes aggregation and the gas molecules adsorbed on the surface of the powder are ionized and replaced. As a result, the wettability with the powder is improved and a stable dispersed state is obtained. Deaerated water can be easily obtained by subjecting ordinary water to a vacuum treatment or a treatment of passing it through a deaeration membrane. Since degassed water does not have gas molecules dissolved therein, gas molecules adsorbed on the surface of the substance are dissolved and the surface of the substance is easily wet.
In particular, for substances having an oxygen concentration of 10 ppm or less dissolved in water and an electric resistance of 1 MΩ or more, various gas ions,
Since the amount of metal ions is small, the substance that causes aggregation is ionized and dispersed, and the gas molecules adsorbed on the surface of the powder are dissolved. As a result, the wettability with the powder is improved as in the case of ultrapure water, and a stable dispersed state is obtained.

[0007]

The present invention will be described in detail with reference to Examples. (Example 1) Using ultrapure water having an electric resistance of 18.1 MΩ as a dispersion medium, SiC powder of known particle size (particle size 0.6 μ)
m) was added, and the ceramic powder was dispersed in water using an ultrasonic dispersing device. The particle size distribution was measured using a laser diffraction type particle size distribution measuring device. As a result, as shown in Table 1, data of particle size distribution having a peak at 0.6 μm was obtained. After the remaining sample was left for 2 hours, the particle size distribution was measured again. As a result, the particle size was 0.6 μm, and reaggregation of particles did not occur.

Example 2 Similar to Example 1, SiC powder having a particle size of 0.6 μm was dispersed in water using degassed water having an electric resistance of 2 MΩ and a dissolved oxygen concentration in water of 5 ppm as a dispersion medium to obtain a particle size distribution. It was measured. As a result, the particle size distribution of 0.6 μm was accurately reproduced. The same result was obtained after standing for another 2 hours.

Comparative Example 1 Pure water having an electric resistance of 15 MΩ was used as a dispersion medium, and the same ceramic material as in Example 1 was used to measure the particle size distribution by the same method. As a result, as shown in Table 1, a particle size distribution having two peaks of 0.6 μm and 2 μm was shown. This indicates that the powder is not well dispersed and is agglomerated. The results are shown in Table 1. The particle size distribution was 0.6 when measured again after being left for 2 hours.
It was found that there were three peaks of μm, 2 μm, and 7 μm, and they were aggregated.

Comparative Example 2 Ion-exchanged water having an electric resistance of 2 MΩ and a dissolved oxygen concentration of 20 ppm was used as a dispersion medium. With the same powder as in Example 1, the particle size distribution was measured by the same method. As a result, a particle size distribution having two peaks of 0.6 μm and 7 μm was shown. Further measurement after standing for 2 hours revealed that the particle size distribution was divided into two peaks of 0.6 μm and 7 μm and aggregated.

Comparative Example 3 Degassed water having an electric resistance of 2 MΩ and a dissolved oxygen concentration of 15 ppm was used as a dispersion medium. The same powder as in the example was used to measure the particle size distribution in the same manner. The results are shown in Table 1. Just like Comparative Example 1, a particle size distribution having two peaks of 0.6 μm and 2 μm was shown. After re-measurement after standing for 2 hours, it was found that the particle size distribution was divided into three peaks of 0.6 μm, 2 μm and 7 μm and aggregated.

Comparative Example 4 Degassed water having an electric resistance of 0.5 MΩ and a dissolved oxygen concentration of 5 ppm was used as a dispersion medium. The same powder as in the example was used to measure the particle size distribution in the same manner. The results are shown in Table 1. Just like Comparative Example 1, a particle size distribution having two peaks of 0.6 μm and 2 μm was shown. After re-measurement after standing for 2 hours, it was found that the particle size distribution was divided into three peaks of 0.6 μm, 2 μm and 7 μm and aggregated.

As described above, according to the dispersion method of the present invention,
While a stable dispersion medium of the ceramic powder can be obtained in a short time and without using a dangerous organic solvent, other than the method of the present invention, secondary agglomerated particles are formed, and an accurate particle size distribution is obtained. I couldn't get it.

[0014]

[Table 1]

[0015]

EFFECT OF THE INVENTION Ultra pure water having an electric resistance of 17 MΩ or more and degassed water having a dissolved oxygen concentration of 10 ppm or less and an electric resistance of 1 MΩ or more are used as dispersion media for dispersing ceramic powder. On the other hand, it provides a method that can disperse safely, reliably, and inexpensively with almost no need for a dispersant. In particular, it improves the reliability of particle size evaluation of ceramic powder and is effective in improving ceramic molding technology. is there.

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Claims (1)

[Claims] 1. A method for dispersing a ceramic powder, wherein either ultrapure water having an electric resistance of 17 MΩ or more or degassed water having a dissolved oxygen concentration in water of 10 ppm or less and an electric resistance of 1 MΩ or more is used as a dispersion medium. A method for dispersing a ceramic powder, which is used.