JPH0733428A - MgO / SiO2 porcelain powder and method for producing the same - Google Patents

Abstract

PURPOSE:To obtain high purity MgO.SiO2 porcelain powder made of a single enstatite phase by making a stock soln. for granulation contg. MgO and SiO2 droplet and subjecting the resulting droplet to drying, thermal decomposition and synthesis. CONSTITUTION:A colloidal soln. of SiO2 is used as starting material for SiO2, magnesium acetate or MgO powder is used as starting material for MgO and they are mixed in 1:1 molar ratio of SiO2:MgO to prepare a stock soln. for granulation. This stock soln. is mode droplet, the resulting droplet is subjected to drying, thermal decomposition and synthesis to form powder and this powder is heat-treated to produce the objective MgO.SiO2 procelain powder made of a single enstatite phase and consisting of spherical solid particles. Since this porcelain powder is spherical MgO.SiO2 porcelain powder made of a single enstatite phase and having a large surface area, it is easy to sinter and can give dense porcelain excellent in electrical prorties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MgO.SiO ₂ porcelain powder and a method for producing the same, and more particularly to an enstatite single phase MgO.SiO ₂ porcelain powder from a liquid phase and a method for producing the same.

[0002]

_2. Description of the Related Art A steatite porcelain is a typical MgO-SiO ₂ system porcelain and has an enstatite phase (M
gO · SiO ₂ ) and the like. Porcelain powder, which is a raw material for such steatite porcelain, is synthesized by decomposing and melting natural raw materials such as talc or silica and magnesia clinker. These natural raw materials include Na, Ca, Fe, B
And impurities such as SiO _{2 and the} like. Further, in order to suppress the phase transition observed in steatite porcelain and prevent the deterioration of porcelain, for example, Al ₂ O ₃ is added to the porcelain in an amount of about 3% to form a glass phase to form clinoenstatite. Blocking is done.

[0003]

However, in the porcelain powder produced by the solid-phase method by decomposition and melting, a plurality of phases such as forsterite (2MgO.SiO ₂ ) and the like are mixed in addition to the enstatite phase. Since the phase transition cannot be controlled during firing, an enstatite single-phase porcelain having excellent electrical properties cannot be obtained. Impurities derived from natural raw materials of porcelain powder or porcelain deterioration inhibitors contained in porcelain deteriorate electrical properties of porcelain. Further, in order to obtain a dense porcelain having excellent electrical properties, it is also necessary to control the particle size and shape of the porcelain powder.

Therefore, an object of the present invention is to provide MgO.SiO ₂ porcelain powder consisting of a single phase of enstatite. In addition, MgO.SiO ₂ which has high purity with controlled impurities and which consists of a single phase of enstatite
The purpose is to provide a porcelain powder. A further object of the present invention is to provide a method for producing MgO.SiO ₂ porcelain powder having a single phase of enstatite. Another object of the present invention is to provide a method for producing a MgO.SiO ₂ porcelain powder having a single phase of enstatite and having a controlled particle size and particle shape.

[0005]

In order to solve the above-mentioned problems, the inventors of the present invention have diligently studied focusing on granulation from a liquid phase without using a solid phase method, and as a result, MgO and SiO ₂
The raw solution for granulation containing is made into droplets, is directly granulated by dry pyrolysis synthesis in a heating furnace, and is thermally treated to form Mg.
_They have found that it is possible to produce O.SiO ₂ porcelain powder.

That is, the inventors have found that MgO.SiO ₂
MgO.Si, which is a porcelain powder, characterized in that the particles constituting this MgO.SiO ₂ porcelain powder are spherical granular solids and consist of an enstatite single phase.
O ₂ porcelain powder was created. In addition, impurities are Al ₂ O ₃
0.50% (meaning% by weight; the same applies hereinafter), CaO 0.50% or less, Fe ₂ O ₃
0.50% or less, TiO ₂ 0.50% or less, Na ₂
The MgO.SiO ₂ porcelain powder was created, which is characterized in that O is 0.50% or less and K ₂ O is 0.50% or less.

Further, the present inventors have found that in the production method of the ceramic powder, a colloidal solution of SiO ₂ as SiO ₂ raw material with magnesium acetate or MgO powder as MgO raw material, as SiO ₂ and MgO is equimolar A step of mixing to form a granulation stock solution, a step of forming the granulation stock solution into droplets, and subjecting the droplets to dry granulation powder by dry pyrolysis synthesis; and a step of heat-treating the granulation powder, A method for producing MgO.SiO ₂ porcelain powder was created, which is characterized by consisting of

Further, the inventors of the present invention have controlled the concentration of MgO and SiO ₂ in the granulation stock solution and / or the speed of introducing the droplets into a heating furnace for dry pyrolysis synthesis, thereby controlling the MgO content. - we have created a method for manufacturing a MgO-SiO ₂ ceramic powder, characterized in that controlling the particle size of the SiO ₂ ceramic powder.

Using the SiO ₂ colloidal solution, the MgO powder and the magnesium acetate means MgO.S
As a raw material for the io ₂ porcelain powder, it means that an industrially refined raw material is mainly used without using a natural raw material, and it is particularly desirable that impurities such as Al, Fe, Ca, Na, K and Ti are small. .

The above-mentioned granulating stock solution may be any one which can be made into liquid droplets by an appropriate means. Therefore, not only a liquid but also a liquid such as a slurry may be used. The droplets are particles made of a liquid or liquid obtained by mechanical or electrical means. The droplet forming means is appropriately selected in consideration of the properties of the undiluted liquid for granulation and the particle size of the obtained granulated particles. For example, relatively large droplets are obtained by simply dropping a liquid or the like, and fine droplets are obtained by atomizing the liquid or the like.

The means for introducing into the heating furnace is appropriately selected in consideration of the properties of the granulated raw material solution and the type of droplet forming means, and is introduced into the heating furnace for aerobically or aerobically performing dry pyrolysis synthesis. It For example, there is a method of aerobically introducing into the heating furnace by using an inert gas such as nitrogen, or a method of introducing into the heating furnace in a gasless manner by injection, dropping or the like. In addition, that the droplets are made into a granulated powder by dry pyrolysis synthesis means that the droplets are directly produced as a solute granular solid by heat and mass transfer in a heating furnace.

[0012] In the said SiO ₂ · MgO ceramic powder and its preparation, contamination-free device of a high-purity raw materials and impurities impurities in other SiO ₂ raw material and SiO ₂ starting material is controlled, using the device, From weighing of each raw material, mixing,
In each of the steps of calcination, pulverization and firing, materials and means that prevent impurities from being mixed into the raw material powder, the synthetic powder, etc. are used, and the purity is always sufficiently considered throughout the steps.

[0013]

[Function] The undiluted liquid for granulation containing equimolar amounts of MgO and SiO ₂ is
It is made into droplets by an appropriate means, dried in a droplet state, pyrolyzed and synthesized to form a granulated powder. Further, the granulated powder is heat-treated to form the particles of the enstatite single phase, thereby obtaining MgO.SiO ₂ porcelain powder. In addition, a solid and spherical fine powder can be obtained by subjecting fine droplets to dry pyrolysis by selecting an appropriate heating furnace introduction method. By controlling the mixing of impurities in the raw material and each step, it is possible to produce a high-purity porcelain powder which has never existed before.

[0014]

【Example】

[Embodiment 1] An embodiment embodying the present invention will be described below with reference to FIGS. This example is an example of the present invention, and the present invention is not limited to this. A process of manufacturing the MgO.SiO ₂ porcelain powder of this example will be described with reference to FIG. First, a high-purity colloidal solution of SiO ₂ as a raw material is diluted with distilled water to obtain SiO _2.
2 concentration is 0.3 mol / l, 0.1 mol / l, 0.0
A 5 mol / l colloidal solution was prepared.

Magnesium acetate tetrahydrate (Mg (CH ₃ COO) ₂ .4H ₂ O), which is a MgO raw material, was weighed and dissolved in this solution so that the molar ratio of SiO ₂ : MgO was 1: 1. , MgO and SiO ₂ are each 0.3 mol / l,
Three types of stock solutions for granulation having concentrations of 0.1 mol / l and 0.05 mol / l were prepared. As the magnesium acetate tetrahydrate used in this example, a reagent special grade was used. The content of the impurities is shown in Table 1.
As shown in. In addition, the SiO ₂ colloidal solution is
Those having pH of 2 to 4, particle size of 10 to 20 nm and purity shown in Table 2 were used. In addition, the-mark in Table 1 and Table 2 indicates
This means that the content is 0.001% or less.

[0016]

[Table 1]

[0017]

[Table 2]

This undiluted solution for granulation is required to be one that does not gel because it is made into droplets. Therefore, the mixing ratio and concentration of each raw material, or the type of SiO ₂ colloid is appropriately selected and used.

These stock solutions for granulation were subjected to dry pyrolysis synthesis by using the spray pyrolysis apparatus shown in FIG. 2 and selecting the pyrolysis temperature and the carrier gas flow rate according to the conditions a to g shown in Table 2. Granulated.

[0020]

[Table 3]

The dry pyrolysis apparatus comprises a granulation stock solution supply section, a pyrolysis reaction section and a collection section for produced particles. In the granulation undiluted solution supply unit, the undiluted solution is mechanically stirred by a magnetic stirrer or the like and is sent by a pump to an ultrasonic atomizer using an ultrasonic vibrator to be a mist (droplet).
The generated droplets are guided to the lower end of the quartz tube which is the thermal decomposition reaction section heated by the carrier gas of nitrogen gas. Then, by moving upward in the heated quartz tube, each droplet is directly granulated by dry pyrolysis synthesis to become one particle, and these particles are electrically adsorbed to the electrostatic collection unit.

The crystalline states of the resulting granulated powders a to g were confirmed by X-ray diffraction. Forsterite (2MgO.SiO ₂ ) and amorphous SiO ₂ were confirmed.
Was confirmed. Further, in the granulated powders b, d to g pyrolytically synthesized at 900 ° C. or higher, enstatite (MgO
· SiO ₂₎ was confirmed while weak the peak of.

With respect to these granulated powders a to g,
The results of measuring the particle size distribution are shown in Table 4. The relationship between the concentration of the undiluted solution for granulation and the particle size distribution is shown in FIG. 3, the relationship between the carrier gas flow rate and the particle size distribution is shown in FIG. 4, and the relationship between the thermal decomposition temperature and the particle size distribution is shown in FIG. In addition, each figure (a) showed the particle size distribution cumulatively, and each figure (b) was shown as a histogram. For the particle size distribution measurement, a laser diffraction scattering type particle size distribution measuring device was used. Further, an enlarged photograph of the granulated powder g is shown in FIG. 6 as an example of the particle shape of the granulated powder.

[0024]

[Table 4]

From the measurement results of the particle size distribution, it was confirmed that the particle size distribution of the granulated powder can be controlled by the concentration of the stock solution for granulation or the carrier gas flow rate. That is, as is clear from FIG. 3, 0.05 mol (MgO.
When SiO ₂ ) / mol, the average particle size is the smallest,
When it is 0.3 mol (MgO.SiO ₂ ) / mol, the average particle diameter becomes the largest. On the other hand, in the concentration range of this stock solution, the higher the concentration, the more the particle size distribution converges to the average particle size. Further, as is clear from FIG. 4, when the carrier gas flow rate is changed in the range of 0.5 to 3 l / min, 3 l
/ Min to 1 l / min, the particle size distribution becomes sharp and the average particle size becomes smaller, but 0.5 l
The average particle diameter increased a little when the value was decreased to / min.
Furthermore, as is clear from FIG.
Even when the temperature was changed in the range of ˜1000 ° C., the particle size distribution and the average particle size did not change so much.

As is clear from the enlarged photograph of FIG. 6, the synthesized particles are spherical and have many wrinkles formed on the surface thereof. The cross section of the spherical particles was confirmed by an electron microscope, and it was found that the particles were solid.

Further, the granulated powders a to g are placed in an electric furnace and heated at 1000 ° C./hour to 1200 ° C.
Alternatively, heat treatment was performed by holding at 1300 ° C. for 1 hour and then allowing to cool. The crystal composition of the obtained MgO · SiO ₂ porcelain powder was confirmed by X-ray diffraction. As shown in FIG. 7, the porcelain powder treated at 1300 ° C. depends on the synthesis conditions of the granulated powder. Without
All of them were almost perfect single phase of enstatite.

In the case of porcelain powder treated by 1200 ° C., granulated powder e having a small average particle size (average particle size: 0.73
However, the enstatite single phase was not formed, and the forsterite phase was the main constituent and the enstatite phase and the crislavite phase were mixed.

That is, a stock solution for granulation in which MgO and SiO ₂ are uniformly mixed is made into fine droplets (atomization), which is granulated by pyrolysis synthesis to directly give a granular solid, which is then powdered.
After generating the enstatite phase in part, 130
By performing the heat treatment at 0 ° C., it was possible to manufacture the MgO / SiO porcelain powder in which the particle size was controlled and which consisted of the enstatite single phase.

Furthermore, since this MgO.SiO ₂ porcelain powder has a solid spherical shape and a controlled particle size, it is convenient for obtaining a dense sintered body. Table 5 shows the result of chemical analysis of the content of impurities in the MgO.SiO ₂ porcelain powder of this example. The-mark in the table indicates
This means that the content is 0.001% or less. In this embodiment, since the raw material having high purity is used, the mixing of impurities is carefully taken into account in the process, and the mixing of impurities is controlled, the amount of impurities in the porcelain powder is almost contained in the raw materials used. It depends on the amount of impurities, and almost the same result is obtained as shown in Table 5.

[0031]

[Table 5]

As described above, MgO · using the spray pyrolysis method
According to the porcelain powder manufacturing method, since the solute that is the raw material is uniformly dissolved, the porcelain powder that is produced has a uniform chemical composition, is spherical, is solid, and has good reactivity during firing. It can be manufactured. Further, the particle size can be controlled by changing the carrier gas flow rate and the solution concentration. Further, since the porcelain powder can be obtained without going through the crushing step, it is possible to surely eliminate the mixing of impurities at the time of crushing, and it is possible to highly control the purity of the porcelain powder.

In this example, the undiluted solution for granulation in which the magnesium acetate tetrahydrate was dissolved in the SiO ₂ colloidal solution was used, but the invention is not limited to this. That is, a liquid or a liquid-state undiluted liquid for granulation may be used as long as it can be formed into droplets by using an appropriate droplet forming (atomizing) means. Therefore, a solution, a colloidal solution, or a slurry can also be used as the undiluted solution for granulation.

[Example 2] Next, as Example 2, Mg
Mg prepared by using high-purity MgO powder as an O raw material
Manufacturing of O.SiO ₂ porcelain powder Figs. 8 to 10
It will be described based on. First, a high-purity MgO powder and a high-purity colloidal solution of SiO ₂ are prepared. In this example, the high-purity MgO powder has a primary particle size distribution of 0.08 to 0.
The high-purity SiO ₂ colloidal solution used was the same as in Example 1 and had a specific surface area of 23 m ² / g. The analysis results of the purity of the high-purity MgO powder used in this example are shown in Table 6. In addition, in Table 6,
The-mark indicates that the content is 0.001% or less.

[0035]

[Table 6]

Next, referring to FIG. 8, the MgO.S of this example is used.
A process of manufacturing the iO ₂ porcelain powder will be described. MgO and S
The MgO powder and the SiO ₂ are mixed so that iO ₂ is equimolar (MgO 1 mol / L, SiO ₂ 1 mol / L).
Weigh and mix the colloidal solution.

Then, the mixture is mixed in a ball mill using urethane balls for 24 hours to obtain a granulation slurry in which MgO and SiO ₂ are uniformly dispersed.

The granulation slurry was agitated by a magnetic stirrer and dropped into a quartz tube of a pyrolysis apparatus heated and held at 800 ° C. through a microtube while ensuring the uniformity of dispersion of each raw material. It is dried and pyrolyzed. When the obtained granulated powder was analyzed by X-ray diffraction, formation of an enstatite phase was confirmed. The result of X-ray diffraction is shown in FIG. The particles of the obtained powder were lumps with a diameter of several millimeters.

After mechanically pulverizing the granulated powder, the temperature was raised at 1000 ° C./hour in an electric furnace, the temperature was maintained at 1300 ° C. or 1400 ° C. for 1 hour, and then the mixture was allowed to cool to heat-treat. MgO.SiO ₂ porcelain powder was obtained. With respect to the obtained MgO.SiO ₂ porcelain powder, formation of an enstatite phase was confirmed by X-ray diffraction. The result is shown in FIG.

As shown in FIG. 10, in the MgO.SiO ₂ porcelain powder heat-treated at 1300 ° C., a slight peak of cristobalite (SiO ₂ ) was observed, but it was almost a single phase of enstatite. It was observed. Also,
With the MgO.SiO ₂ porcelain powder heat-treated at 1400 ° C., it was possible to synthesize a powder consisting of a single phase of enstatite.

That is, a slurry in which a high-purity MgO powder and a high-purity SiO ₂ solution are uniformly mixed is dropped into a heating furnace for dry pyrolysis synthesis, and a granule having a part of an enstatite phase. And then 1300-1
By performing the heat treatment at 400 ° C., it was possible to manufacture the MgO.SiO porcelain powder consisting of the enstatite single phase. In Table 7, as in Example 1, the MgO.S of this example was used.
The chemical analysis of impurity content in iO ₂ ceramic powder. Also in this example, it was confirmed that the content of impurities in the raw material was determined by the content of impurities in the porcelain powder.
In addition, the-mark in the table indicates that the content is 0.001% or less.

[0042]

[Table 7]

[0043]

As described above in detail, according to the porcelain powder of the present invention, since it is a spherical MgO.SiO ₂ porcelain powder having a single phase of enstatite and a large surface area, it is easy to sinter and is dense and electric. It is possible to obtain a porcelain having excellent physical properties. Also, by controlling the impurities in the porcelain powder,
High-purity porcelain powder can be obtained, and deterioration of electrical properties due to impurities in the porcelain can be prevented. Further, according to this method for producing MgO.SiO ₂ porcelain powder, the enstatite single-phase Mg is directly granulated from the liquid phase by dry pyrolysis synthesis by forming droplets and heat-treated.
O.SiO ₂ porcelain powder can be obtained. Furthermore, it is possible to control the particle size distribution by the concentration of the undiluted granulation liquid or the flow rate of the carrier gas that introduces the liquid droplets into the heating furnace, and it is possible to obtain the MgO.SiO ₂ porcelain powder having a particle size as required.

[Brief description of drawings]

FIG. 1 is a process drawing of obtaining MgO.SiO ₂ porcelain powder of the present invention by spray pyrolysis.

FIG. 2 is an overall view of a dry pyrolysis synthesis apparatus.

FIG. 3 is a graph showing the relationship between the concentration of the undiluted granulation solution and the particle size distribution.

FIG. 4 is a graph showing the relationship between carrier gas flow rate and particle size distribution.

FIG. 5 is a graph showing the relationship between thermal decomposition temperature and particle size distribution.

FIG. 6 is an enlarged photograph of particles by dry pyrolysis synthesis.

FIG. 7 is a diagram showing a crystal composition of MgO.SiO ₂ porcelain powder by X-ray diffraction.

FIG. 8 is a process diagram for obtaining the MgO.SiO ₂ porcelain powder of the present invention by dropping thermal decomposition.

FIG. 9 is an X-ray diffraction pattern of the granulated product.

FIG. 10 is an X-ray diffraction diagram of MgO.SiO ₂ porcelain powder.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehisa Fukui 3 from 6-28, Kyowa-cho, Obu City, Aichi Prefecture (72) Inventor Yutaka Higashida 3 from 2--18, Mitsugaoka, Komaki City, Aichi Prefecture (72) Inventor Kaku Tsutomu Oka 3 No. 25, Dandome, Kariya city, Aichi prefecture

Claims (4)

[Claims] 1. A MgO.SiO ₂ porcelain powder, characterized in that the particles constituting the MgO.SiO ₂ porcelain powder are spherical granular solids and consist of an enstatite single phase. SiO ₂ porcelain powder. 2. The impurity according to claim 1, wherein the impurity is Al ₂ O ₃
0.50% or less, CaO 0.50% or less, Fe ₂ O ₃ 0.50% or less, TiO 0.50% or less, Na ₂ O 0.50% or less, K ₂ O 0.50% or less M characterized by
gO ・ SiO ₂ porcelain powder. 3. A method for producing a porcelain powder, wherein a SiO ₂ colloidal solution is used as a SiO ₂ raw material, and magnesium acetate or MgO powder is used as a MgO raw material.
Mixing O ₂ and MgO in equimolar amounts to form a granulation stock solution, and forming the granulation stock solution into droplets and subjecting the droplets to dry pyrolysis synthesis to form a granulated powder And a step of heat-treating the granulated powder, and a method for producing the MgO.SiO ₂ porcelain powder. 4. The M in the stock solution for granulation according to claim 3.
The particle size of the MgO.SiO ₂ porcelain powder is controlled by controlling the concentration of gO and SiO ₂ and / or the rate of introducing the droplets into a heating furnace for dry pyrolysis synthesis. Method for producing SiO ₂ porcelain powder.