JPH0644990B2 - Manufacturing method of composite fine powder material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention fluidizes a fine powder, and uses a complete dry process.
The second component is a gas phase reaction method (Chemical Vapor Deposition, CV
The method D) relates to a method for continuously producing extremely homogeneous composite ultrafine powder by depositing on the fine powder.

[Conventional technology]

Conventionally, when it is attempted to uniformly mix a plurality of ultrafine powders to produce a composite fine powder material, the fine powders produced separately in advance are mixed by applying strong energy with a vibrating ball mill or the like. It is normal. Even if mixed in a mortar, the ultrafine powder does not mix at all. In a high-energy mixer such as a vibrating ball mill, the mixer itself is also crushed, so that contamination of fine powder cannot be avoided.

Further, when the fine powder is sintered and molded, the fine powder is rarely sintered alone, and a sintering aid is often added. Usually, the fine powder is dipped in a solution in which the auxiliary agent is dissolved and then dried. However, when drying the ultrafine powder,
Uneven distribution of the solution occurs, and it is difficult to mix the auxiliary agent uniformly.

Japanese Patent Laid-Open No. 63-55112 discloses that in a fluidized bed reactor heated by ultrashort waves, silane, 2
A method and an apparatus for producing high-purity polycrystalline silicon in which silicon is deposited by chemical vapor deposition by thermal decomposition or hydrogen reduction reaction of silicon-containing gas of silane chloride, silane trichloride, and silane tribromide are described. The above publication is a fluidized bed CVD
The present invention relates to a method for producing silicon by (gas phase reaction method), not to a composite fine powder material.

Japanese Unexamined Patent Publication No. 63-216904 has a core having magnetism and a coating layer for coating the core, and the coating layer includes Ti and N.
Magnetic particles containing C and / or C or containing Al and N and methods of making the same are described. In the above publication, magnetic particles are manufactured by a method of forming a coating layer by a plasma CVD method while applying vibration to the core.

This Japanese Patent Application Laid-Open No. 63-216904 discloses a composite fine powder material in which another substance is deposited on the surface of a particle by CVD to modify it. That is, as shown in FIG. 2, the surface of the substance A is coated with the substance B by CVD. Therefore, the produced substance is a method of modifying the surface such that it is mechanically A but chemically B.

[Problems to be Solved by the Invention]

Generally, powders with particle sizes smaller than 30-40 μm are
Liquidation is said to be extremely difficult.

The present inventor has conducted various researches and experiments on fluidization of fine powder, and as a result, particles with a particle diameter of 10 μm or less have a special vibration,
Even without stirring, if the gas flow rate is set to several cm / s or more,
We have found that they can be sufficiently fluidized.

The present invention has been made in view of the above points, fluidizes the ultrafine powder used for the composite fine powder material, and introduces the second component to be mixed in the fluidized bed by gas, and the gas phase reaction method ( C
It is an object of the present invention to provide a method for producing an extremely homogeneous composite by precipitating it on ultrafine powder particles which is a fluid medium by means of chemical vapor deposition.

[Means and Actions for Solving the Problems]

In order to achieve the above object, a method for producing a composite fine powder material according to the present invention comprises fluidizing a first fine powder to form a fluidized bed, and forming a second fine powder in a gaseous state in the fluidized bed. Blow in to deposit the second fine powder on a part of the first fine powder,
It is intended to produce a homogeneous composite fine powder.

It is desirable that the first fine powder be fluidized near atmospheric pressure.

Further, coarse particles larger than the first fine powder may be added to the fluidized bed and fluidized in the fluidized bed.

Furthermore, vibration or agitation may be added to the fluidized bed.

A plurality of fine powders in the fluidized bed are associated with each other to form agglomerates. By adjusting the reaction conditions, not only the surface of the agglomerates but also the inside of the agglomerates, that is, the surfaces of the individual first particles can be uniformly deposited. When fluidizing coarse particles with a diameter of 1 to 20 mm in a fluidized bed to maintain the fluidization of ultrafine powder, or when vibrating or agitating the fluidized bed, agglomerates are not formed and fine powder is generated. Although the body may be dispersed and fluidized, naturally, in this case as well, uniform precipitation of the second component is obtained.

Hereinafter, the method of the present invention will be described in detail with reference to FIG. The diluting nitrogen passes through the stop valve 2 of the nitrogen cylinder 1, the pressure is controlled by the pressure control device 3, and the flow rate is measured by the manometer 4. Oxygen is removed by the oxygen absorbing device 5, and water is removed by the dehydrating devices 6 and 7. This nitrogen line has two series, and one of the nitrogen lines is mixed with ammonia from the ammonia cylinder 8 and the pressure is controlled by the pressure control device 10,
After passing through the stop valve 11, the flow rate is measured by the manometer 12, the water is dehydrated by the dehydrator 13, and then the liquid is fed from the nozzle 14 into the fluidized bed 15.

Another series of nitrogen is sent to a titanium chloride (TiCl ₄ ) evaporator 16 to dilute the titanium chloride gas and then blown into the fluidized bed 15.

The fluidized bed 15 is made of, for example, fine powder silicon nitride, is mixed with titanium nitride deposited in the fluidized bed, jumps out, and is collected by the filter 17 to be a product. 1
8 and 20 are thermometers, 21 is a packed bed (gas disperser), 22 is a heater, and 23 is an absorber of ammonia and titanium chloride.

The present invention shows a mere mixing method of the substance A and the substance B, and is not intended for CVD deposition on the surface of the substance.

When the fine powders of the substance A and the substance B are mechanically mixed, they are not uniform as shown in FIG. 3 because of the small particle size.

Therefore, the substance A or B is fluidized and the other substance B or A is
Fig. 4 shows the result of CVD deposition. That is,
The substance A and the substance B exist for each particle, and the substance A and the substance B are uniformly mixed as a whole. Precipitation by CVD does not require any uniform coating of the particle surface and therefore no modification, only that the substance A and the substance B are uniformly mixed. The present invention is capable of the above.

〔Example〕

 Next, examples will be described.

Example 1 This example relates to a method for depositing titanium nitride on silicon nitride fine powder. Although silicon nitride is an excellent high temperature material, it cannot be electric discharge machined because it has no electrical conductivity. Therefore, by mixing titanium nitride having electrical conductivity with silicon nitride and sintering the mixture, silicon nitride capable of electric discharge machining can be obtained. In the past, since the silicon nitride fine powder and the titanium nitride fine powder were mixed, it was necessary to mix titanium nitride in an amount of about 20 wt% in order to obtain electric conductivity capable of electric discharge machining.

As the oxygen absorber 5 in FIG. 1, nitrogen was deoxidized using a tank filled with activated copper, and dehydrated using a dehydrator 6 (tank filled with silica gel) and a dehydrator 7 (dry ice trap). Dilute ammonia, nozzle 14
Was blown into the fluidized bed 15 having an inner diameter of 35 mm. The deoxygenated and dehydrated nitrogen is passed through a titanium chloride vaporizer 16 in which a titanium chloride container is kept in a constant temperature bath to vaporize a fixed amount of titanium chloride, and a fluidized bed 1 is introduced from an inlet different from ammonia.
I blew in 5. In the fluidized bed 15, the submicron silicon nitride fine powder was fluidized with deoxidized and dehydrated atmospheric pressure nitrogen at a temperature of 1100 ° C. The particles that jumped out were collected in the filter 17 using filter paper. The flow rate of titanium chloride was calculated based on the flow rate (measured) of ammonia by analyzing the gas at the fluidized bed outlet.

The obtained fine powder was a mixture of silicon nitride fine powder and titanium nitride fine powder. The crystallite size of the obtained titanium nitride increased with the precipitation amount of titanium nitride and decreased with the increase of the reaction temperature, and was in the range of 20 to 100 nm. As a result of measurement by an X-ray microanalyzer, electron diffraction, and a transmission electron microscope, it was shown that the mixture of silicon nitride and titanium nitride was extremely uniform. 1700 this fine powder
When the electrical conductivity was measured by sintering in a nitrogen atmosphere at ℃ or higher, a sintered body sufficiently suitable for electrical discharge machining was obtained. When silicon nitride and titanium nitride fine powder are manufactured and then mixed, the amount of titanium nitride is required to be about 20 wt% in order to obtain practical electric conductivity. Fell below.

In this example, it is desirable to keep the temperature of the fluidized bed at 500 to 1200 ° C.

Example 2 This example relates to a method for producing a composite fine powder of alumina and titania. When the submicron alumina fine powder was fluidized with atmospheric air dried in the fluidized bed 15 and kept at 1200 ° C. and titanium chloride vapor was fed,
Mixed ultrafine particles of alumina and titania were obtained. As a result of measurement by X-ray diffraction, an X-ray microanalyzer, an electron microscope, etc., it was found that alumina and titania were uniformly mixed. After the reaction, the fluid state was good, and the layer did not clog.

In this example, it is desirable to keep the temperature of the fluidized bed at 800 to 1300 ° C.

Example 3 This example relates to a method for producing a composite fine powder of alumina and titania in a fluidized bed in which medium particles are fluidized.

In the system of Example 2, in order to improve the flow state, the diameter of 1 ~
Classified alumina particles in the range of 5 mm were fluidized with air, and fine alumina powder was fed into the fluidized particles, and fluidized with coarse alumina particles. The fluidized state was further improved as compared with the fluidized bed of the fine alumina powder alone. Titanium chloride was fed thereinto to deposit fine titania powder. In this embodiment,
The degree of mixing of the alumina and the titania fine powder was further improved as compared with Example 2, but the amount of the fine powder jumped out increased. However, when the amount of the second component to be precipitated by the vapor phase reaction method (Chemical Vapor Deposition) may be small, the reaction occurs sufficiently quickly, and even if there is a jump out, it did not hinder the operation. . Further, by continuously supplying the ultrafine alumina powder into the fluidized bed and continuously ejecting it, the alumina / titania mixed fine powder could be continuously produced.

In the embodiments of the present invention, a fluidized bed that is not subjected to vibration or stirring is used, but a fluidized bed to which mechanical energy such as vibration or stirring is added may be used. In any case, it is characterized in that the fine powder is brought into contact with a gas in the vicinity of normal pressure in a moving state, and the second component is added by a dry process by a gas phase reaction method. The powder can be continuously supplied or discharged, but the charged powder may be processed in a batch system or a semi-batch system.

The above embodiments are examples and not all.
The present invention includes a method of fluidizing a powder by some method under normal pressure or a pressure close thereto and producing a composite powder by a dry process by a gas phase reaction method, or modifying the surface of the powder. To do.

〔The invention's effect〕

Since the present invention is configured as described above, it is possible to mix ultrafine powders in the gas phase, which was not possible conventionally, and the uniformity of mixing is extremely high. It is possible to produce a composite fine powder material of excellent quality in which the second fine powder is deposited on a part of the above. In addition, the use of a solvent is unnecessary and the drying process is also unnecessary.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of an apparatus for carrying out the method for producing a composite fine powder material of the present invention, and FIG. 2 shows a conventional method, in which another substance is deposited on the particle surface by CVD as a composite fine powder material. Conceptual diagram when reforming, FIG. 3 shows a conventional method, a conceptual diagram when mechanically mixing fine powders of A and B,
FIG. 4 shows the method of the present invention, and is a conceptual diagram when the substance A or the substance B is fluidized and another substance B or the A is deposited by CVD. 1 ... Nitrogen cylinder, 2, 11 ... Stop valve, 3, 10 ... Pressure control device, 4, 12 ... Manometer, 5 ... Oxygen absorption device, 6, 7, 13 ... Dehydration device, 8 ... Ammonia cylinder, 14 ... Nozzle, 15 ... Fluidized bed, 16 ... Titanium chloride vaporizer, 17 ... Filter, 18, 20 ...
… Thermometer, 21… Packed bed, 22… Heater, 23…
... Ammonia and titanium chloride absorber

Claims (3)

[Claims] 1. A fluidized bed is formed by fluidizing a first fine powder, and a second fine powder is blown into the fluidized bed in a gaseous state to form a second layer on a part of the first fine powder. Of fine powder of
A method for producing a composite fine powder material, which comprises producing a uniform composite fine powder. 2. The method for producing a composite fine powder material according to claim 1, wherein coarse particles larger than the first fine powder are added to the fluidized bed and fluidized in the fluidized bed. 3. The vibration or stirring is applied to the fluidized bed.
A method for producing the composite fine powder material as described.