JPS61257227A - Production of fine powder - Google Patents

Abstract

PURPOSE:To prevent change in qualities due to the oxidation or the like and to obtain fine powder for easy molding in case of producing the fine power of the raw material of a sintered body in a vapor phase process by suspending the collected fine powder in a solvent nonreactive with this fine powder, adding a binder, drying and granulating the mixture. CONSTITUTION:The fine powder of silicon nitride or the like produced by laser irradiation is collected in a dry type with a filter and an electrostatic separation method. The collected fine powder is sent to a slurrying process in such a state that the contact with the outside air is interrupted and mixed with the solvent nonreactive with the fine powder of normal paraffin of the like and dried with the hot air and granulated after adding a binder such as was. The area exposed to the atmosphere is decreased by the granulation and the deterioration in the purity and the change in qualities due to O2 and water content are decreased and the fluidity is enhanced because the bulk density is made large and the molding is made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing fine powder, and particularly to a method for producing fine powder as a raw material for a sintered body by a vapor phase method.

[Conventional technology]

In recent years, in the field of new materials, research on ultrafine particles has been active with the aim of creating new functions. Ultrafine particles are generally 0.1μ
It refers to particles of 5K (10001) or less, and there are liquid phase methods and gas phase methods for manufacturing them.The gas phase method related to the present invention is explained as follows. Once vaporized, it is cooled to produce a fine powder.

(2) A gaseous substance is irradiated with Rede light to cause a chemical reaction and then cooled to produce fine powder.

(3) A gaseous substance is turned into plasma to cause a chemical reaction mainly centered on radicals, and then cooled to produce fine powder.

(4) Gaseous substances are heated to cause a chemical reaction through thermal decomposition, and then cooled to produce fine powder.

Various methods can be mentioned.

By the way, 5-sized particles are suspended in the airflow,
It is collected and separated from the gas phase using filters, electrostatic separation methods, etc. In addition, the ultrafine particle size of the sintered body raw material powder is
Progress is being made with the aim of significantly improving the physical properties of sintered bodies and saving energy by increasing the sintering rate, increasing the densification rate, low-temperature sintering, low-pressure sintering, short-time sintering, and suppressing grain growth.

[Problem that the invention seeks to solve]

However, according to the prior art, the particle size of the collected fine particles is small, so there are the following drawbacks.

■ Because it has a large surface area and is active, it can absorb moisture and oxygen.
Or, due to oxidation, the purity may decrease, the quality may deteriorate, and in extreme cases, it may burn.■ When used as a raw material for sintered bodies, such as ultrafine ceramic powder, it has poor fluidity and low bulk density (fluffy). Therefore, it is difficult to mold.

The present invention was made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a method for producing fine powder that can protect the surface from contamination by oxygen and moisture and is easy to mold.

[Means for solving problems]

The present invention is a method for producing fine powder as a raw material for a sintered body by a vapor phase method, in which the generated fine powder is collected, and then this fine powder is suspended in a solvent that is inert to the fine powder. It is characterized by adding a binder to the suspension, drying it and granulating it. Specifically, the present invention consists of steps (1) to (4) shown below.

(1) First, the collected fine powder is put into a solvent that does not react with the fine powder (for example, normal graphin) to form a suspension.

■ Next, add 1 the above suspension to a solvent-soluble pine paste (e.g., t
)-3' Waxes, ? (e.g. lipinyl alcohol).

(2) Next, the above suspension (2) is supplied to a spray dryer, where it is granulated and dried to form a product.

[Effect]

According to the present invention, (1) By putting the collected fine powder into a solvent that does not react with the fine powder to form a suspension, contact with air can be avoided and it can be taken out into the atmosphere, making it easy to transport and handle. Become.

(2) By adding a binder to the suspension and spray drying it, the granules are granulated, increasing the bulk density and improving fluidity, which solves problems in molding.

■ Granulation reduces the area exposed to the atmosphere, reducing oxidation and
The degree of purity deterioration and deterioration due to oxygen and moisture adsorption is reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

1 in the figure indicates a reaction product gas line. This reaction product gas line! The reaction product gas inside contains fine powder produced by a chemical reaction.

This gas is first introduced into a fine powder separation step 2 and is dry-collected, for example, by a filter or electrostatic separation method. The gas from which fine powder has been removed is discharged.

In the separation step 2, consideration is given to preventing leakage of air in order to prevent deterioration of the fine powder and deterioration of purity due to oxygen and moisture. The collected fine powder is sent to the slurry-forming step 5 via the collected fine powder take-out line 4 in a state where contact with the outside air is cut off, and is mixed with the solvent supplied from the solvent supply line 6.

The fine powder slurry is extracted from the slurry extraction line r, mixed with powder supplied from the powder supply line 8, and sent to the drying and granulation step 9. In the dry granulation step 9, the sprayed solvent droplets are dried by hot air supplied from the hot air supply line 10, and the fine powder contained therein is solidified by pine paste. Then, it is produced as a granulated powder and extracted from the product extraction line 11. After the drying hot air is separated from the granulated powder, it is discharged from the dry exhaust gas line 12.

Specific Example 1 A mixed gas of silane gas, anthonia gas, and argon was supplied into a reactor in an argon atmosphere, and the mixed gas was irradiated with CO2 radar to generate fine powder of silicon nitride. Here, the supply rate of silane gas is 140"15),
Ammonia gas is 190”7%, argon is 1330°
ν minutes.

Subsequently, the generated fine powder was collected with a filter, the holder was disassembled in a glove and gas exchanger replaced with argon gas, and the fine powder was suspended in the fine normal heptane on the filter. The suspension was then removed from the glow tube into the atmosphere. As a result of observation using an electron microscope, the particle diameter of the fine powder was approximately 90X. Next, 2% by weight of a commercially available wax-based binder fine powder was added to this suspension and stirred to dissolve it. Next, this suspension was supplied to a spray dryer, dried at 170°C, and granulated. The obtained granulated powder was spherical particles of about 50 μm. Note that heated air at 250° C. was used as the heat source. Further, the exhaust gas after separating the granulated powder was subjected to indirect heat exchange with a refrigerant at about 1° C., and normal hebutane was dragged therethrough.

According to the present invention, when the granulated powder was analyzed to determine the oxygen content, it was found to be 1.2"t'16, which is equivalent to commercially available silicon nitride powder (average particle size of about 0.6 μm). can be,
It is clear that the surface of the ultrafine powder of about 901 (0,009 μm) is protected from oxygen and moisture by the present invention. Therefore, the degree of purity deterioration and deterioration is reduced compared to the conventional method.

In addition, by putting the collected silicon nitride fine powder into normal hegetane that does not react with the fine powder and making it into a suspension, contact with air can be avoided and it can be taken out into the atmosphere.
Transportation and handling become easier. Furthermore, when pine/ is added to the 1 suspension and spray-dried, the granules are granulated and the bulk density is increased, and the fluidity is also improved, which solves the problems in molding.

Specific Example 2 A mixed gas of silane gas, ethylene gas and ζnitrogen gas is supplied into a reactor in a nitrogen gas atmosphere, and this mixed gas K Co
2 lede was irradiated to produce fine powder of silicon carbide.

Here, the supply rate of silane gas is 660ee/%, ethylene gas is 3306 liters, and nitrogen gas is 1010'! e/
+ Subsequently, the resulting fine powder was dried and granulated using a spray dryer in the same manner as in Example 1. The particle diameter of the fine powder is approximately 450X, and the particle diameter of the granulated powder is approximately 5X.
It exhibited a spherical shape of 0 μm. However, when oxygen in the granulated powder was analyzed, the effect of the present invention was clear at 0.95 wt %.

Note that the fine powder is solidified with a binder, and the appearance is that of the upper hook 5.
Although the thickness is 0 μm, the properties during sintering are not impaired. Furthermore, the method of the present invention is not limited to vapor phase synthesis using Rede.
It can also be applied to sintered body raw materials produced by each of the above-mentioned vapor phase synthesis methods.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a method for producing fine powder that can protect the surface from contamination by oxygen and hydrogen and has various effects such as ease of molding.

[Brief explanation of drawings]

The figure is an explanatory diagram of the method for producing fine powder according to the present invention. 1... Reaction product gas line, 2... Separation process, 3
... Exhaust gas line, 4... Collection fine powder extraction line, 5... Slurrying process, 6... Solvent supply line, 7
. . . Slurry extraction line, 8. Binder supply line, 9. Drying granulation process, 10. Hot air supply line, 11. Product extraction line, 12. Drying exhaust bus line. To procedural amendment book α7. i8a Michibe Uga, Commissioner of the Patent Office1, Indication of the case, Patent Application No. 1988-990152, Name of the invention, Process for producing fine powder3, Person making the amendment, Relationship with the case, Patent applicant (620), E. Heavy Industries Co., Ltd. 4a Agent 5, Voluntary Amendment 7, Contents of Amendment (1) On page 7 of the specification, lines 4-5, it is stated that ``Commercially available wax-based pine paste was dissolved in fine powder by mooring 2 weights of powder and stirring. 2 weight of commercially available wax-based binder (made by Chukyo Yushi ■; trade name Maxelon A (40% liquid), trade name Maxelon M (40% liquid)) for fine powder. The mooring was stirred and dissolved. Here, 1 wax-based binder to 2 weights of fine powder.
．． 511 (solid content 1g excluding solvent) and Maxelon M
is corrected to mean that 2.5Ii (solid content II excluding solvent) was added. (2) After the sentence "It is clear..." on page 7, line 17 of the Meijusho, there is a statement that says, "The trade name of the commercially available silicon nitride powder mentioned above is 8N9B (Denki Kagaku Kogyo ■). The following text is added: "Manufactured by Si nitriding method."

Claims (1)

[Claims] In a method for producing fine powder as a raw material for a sintered body by a vapor phase method, the fine powder produced is collected, suspended in a solvent that is inert to the fine powder, and then a binder is added to the suspension. A method for producing a fine powder, which comprises adding and then drying and granulating the powder.