JPS6132252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing ultrafine powder of a carbide such as silicon or titanium, which is used as a highly heat-resistant material, for example.

Conventionally, gas phase reaction methods and liquid phase reaction methods have been used to produce fine powders such as silicon carbide and titanium carbide, but the diameters of the fine powders obtained by these methods are small, even if they are small. It is approximately 0.2 μm and is often contaminated with impurities.

By the way, when molding a high-strength heat-resistant material by sintering fine carbide powder, it is known that the smaller the particle size, the lower the sintering temperature, and the smaller the amount of impurities mixed in, the higher the strength.

Therefore, it has been desired to develop a method and an apparatus for producing ultrafine powder with a small particle size without contamination with impurities.

The present invention aims to meet such demands, and applies a so-called gas evaporation method to evaporate silicon, titanium, etc. into a vacuum vessel into which a working gas of a compound containing a carbon component at a required pressure is introduced. An object of the present invention is to provide a method and an apparatus for obtaining carbide as an ultrafine powder with a small particle size and few impurities.

For this reason, the method for producing ultrafine carbide powder of the present invention involves bringing a current-carrying member made of carbon or the carbide into contact with a material such as silicon, titanium, or the carbide thereof in a vacuum container into which a working gas at a required pressure is introduced. In the method for obtaining the ultrafine powder of carbide such as silicon or titanium through high-temperature reaction by applying electricity, the working gas is characterized in that the working gas is a compound containing a carbon component.

Furthermore, the production apparatus of the present invention used in the above method is equipped with a vacuum vessel into which a working gas of a compound containing a carbon component at a required pressure is introduced, and in this vacuum vessel, materials such as silicon, titanium, etc. or their carbides are In order to generate ultrafine powder of a carbide such as silicon or titanium, a support stand capable of supporting the same material and an electrically conductive member of carbon or a carbide such as silicon or titanium held on the support stand so as to be able to contact the above-mentioned material. a gripping member that can hold the material, an electrical wiring that can supply electricity to the material and the current-carrying member through their contact portions and the support base, and a lifting mechanism that can hold the current-carrying member in contact with the material; A gas supply means capable of supplying the working gas so as to surround the material is provided, and the gas supply means includes an annular nozzle formed on the support base and capable of ejecting the working gas so as to surround the material. , and a working gas supply path bored in the support base to supply the working gas from the working gas supply source to the annular nozzle.

Hereinafter, an apparatus used in a method for producing ultrafine silicon carbide powder as an embodiment of the present invention will be explained with reference to the drawings.
The figures are all graphs for explaining the effect, and a solid silicon block 3 as a raw material is placed on a support base 2 made of carbon material in a vacuum container 1.

A current-carrying member 4 made of a rod-shaped carbon material and in contact with the upper surface of the silicon block 3 is held and suspended by a gripping member 5 made of carbon material. is supported by Therefore, although the current-carrying member 4 is held in contact with the silicon block 3 by the lifting mechanism 7,
The silicon block 3 may be moved up and down.

Further, a current-carrying electric wire 8 is connected to the support base 2, and another current-carrying electric wire 9 is connected to the gripping member 5, and each electric wire 8, 9 can be changed by switching a changeover switch (not shown). It can be connected to an auxiliary power source for preheating or to the main power source.

As a result, when each electric wire 8, 9 is connected to the auxiliary power source, the silicon block 3 can be preheated to lower its electrical resistance value, and when each electric wire 8, 9 is connected to the main power source, the current-carrying member 4. Electric current is passed through the contact portion 10 between this and the silicon block 3, the silicon block 3, and the support base 2 to generate heat and heat the silicon block 3 and the current-carrying member 4 themselves.

Further, the support stand 2 is supported on the bottom face of the vacuum vessel 1 via an insulator 2a so that there is a slight gap between the support stand 2 and the bottom face of the vacuum vessel 1 below the support stand 2. An opening is formed, and this opening is connected to a vacuum pump P via a duct 1a.

Therefore, the air inside the vacuum container 1 is transferred to the duct 1a.
It can be extracted using a vacuum pump P.

By the way, a nozzle 11 having an annular groove is formed on the surface of the support base 2 on which the silicon block 3 is placed.
1 is a working gas supply path 1 bored in the support base 2;
It is connected to one end of 2.

The other end of the working gas supply path 12 is open to the side surface of the support base 2, and this other end opening contains a carbon component via an insulator 12a and a working gas supply pipe 14 with an on-off valve 13. It is connected to a working gas source (not shown) which supplies methane gas as a working gas consisting of a compound.

In this way, the annular nozzle 11, the working gas supply path 12, etc. constitute a gas supply means G, and this gas supply means G surrounds the silicon block 3 as shown by the arrow a in FIG. Methane gas can be supplied from the annular nozzle 11 as shown in FIG.

In this way, a curtain of methane gas is formed to surround the silicon block 3, and the contact portion 10 between the silicon block 3 and the current-carrying member 4 is also surrounded by the methane gas curtain. After the methane gas forms a gas curtain in this way, it diffuses into the vacuum container 1 and increases the pressure inside the vacuum container 1, but since this methane gas is appropriately exhausted through the exhaust pipe 16 with the on-off valve 15, The inside of the vacuum container 1 is maintained at approximately a predetermined pressure.

The elevating mechanism 7 is capable of elevating and lowering a rod 7b connected to the gripping member 5 via an electrically insulating plate 6 by pulling up or pushing in a knob 7a provided outside the vacuum container 1. However, it is also possible to make this electric.

Using the apparatus described above, the method of the invention is carried out as follows. First, the electric wires 8 and 9 are connected to the auxiliary power source, the silicon block 3 is preheated to reduce the electrical resistance value of the silicon block 3, and then the electric wires 8 and 9 are connected to the When connected to the main power source and energized to the support base 2, silicon block 3, and current-carrying member 4, the current-carrying member 4 becomes incandescent, and the silicon block 3 is welded at the contact portion 10 with the current-carrying member 4, and the surface tension reacts at high temperature while wetting the current-carrying member 4, generating carbide as a compound of silicon and carbon, that is, vapor or clusters of silicon carbide.

At this time, unreacted silicon vapor or clusters are also generated, but since methane gas is injected from the annular nozzle 11 so as to surround the silicon block 3 and the contact portion 10 between this and the current-carrying member 4, the unreacted silicon vapor or clusters are generated. The reacted silicon reacts efficiently with the carbon component contained in the injected methane gas and turns into silicon carbide vapor or clusters.

These silicon carbide vapors or clusters are converted into ultrafine powder that looks like smoke by the action of methane gas introduced into the vacuum container 1.

In this way, ultrafine silicon carbide powder containing less unreacted silicon can be obtained, but as can be seen from Figure 2, this is because the flow rate of methane gas (CH ₄
The higher the methane gas pressure in the vacuum container 1, the better the efficiency is.

As the reaction progresses, the current-carrying member 4 is lowered and pushed into the molten portion of the silicon block 3 using the elevating mechanism 7 as appropriate so that the silicon block 3 and the current-carrying member 4 are not separated from each other.

The ultrafine silicon carbide powder thus produced adheres to the inner wall of the vacuum vessel 1, so that it can be collected by scraping it off after the reaction is completed.

In the experimental example, the current-carrying member 4 has a diameter of 5 to 6 mm.
A carbon rod of approximately 300 amperes was passed through the rod to obtain ultrafine powder with a diameter of 30 nm or less.

In addition, in order to obtain ultrafine powder with small particle size,
As shown in FIG. 3, it was also found that the gas pressure inside the vacuum container 1 could be lowered.

As the working gas, in addition to methane gas, acetylene gas, benzene gas, or a mixed gas of these gases with hydrogen gas or inert gas can also be used.

Furthermore, instead of supplying the working gas into the vacuum chamber 1 through the nozzle 11 having an annular groove as in the above embodiment, a small hole communicating with the working gas supply path 12 is provided around the silicon block 3 in an annular shape. It is also possible to supply the working gas into the vacuum vessel 1 through a nozzle arranged in the vacuum vessel 1 .

Furthermore, if the pressure inside the vacuum container 1 is kept high, high purity silicon carbide can be obtained without continuously supplying the working gas. In this case, the gas supply means G consisting of an annular nozzle etc. No longer needed.

If a metal such as titanium is used instead of silicon as a material, it has sufficient conductivity itself, so preheating through an auxiliary power source is not necessary. , it is necessary to conduct a larger current than in the case of silicon.

Further, in addition to using silicon, titanium, etc. as the material, carbides thereof can also be used, and furthermore, instead of using carbon, carbides such as silicon and titanium can also be used as the current-carrying member.

As detailed above, according to the method for producing a carbide of the present invention, the reaction between a material such as silicon, titanium, or a carbide thereof and a current-carrying member made of carbon or a carbide such as silicon or titanium is promoted in a high temperature state by energization. As a result, ultrafine carbide powder can be produced extremely efficiently, and during production, the reaction product is turned into ultrafine powder, except for materials such as silicon and electrically conductive parts inside the vacuum vessel as a reactor. At the same time, only a working gas consisting of a compound containing a carbon component is introduced to react with unreacted silicon, titanium, etc. to form carbides.
The possibility of contamination with impurities is extremely reduced,
It has the advantage of being able to obtain ultrafine carbide powder with high purity.

Further, according to the manufacturing apparatus of the present invention, since a lifting mechanism that can maintain the current-carrying member at a required level is provided, it is possible to always make stable and reliable contact of the current-carrying member to the material, and the annular nozzle and By providing a gas supply means configured with a working gas supply path, the working gas can be supplied so as to surround the above-mentioned material, and the reaction with unreacted silicon, titanium, etc. can be completed. This has the effect of efficiently producing ultrafine carbide powder with high purity.

[Brief explanation of the drawing]

The figure shows an apparatus used in a method for producing ultrafine carbide powder as an embodiment of the present invention.
The figure is a longitudinal sectional view, and both Figures 2 and 3 are graphs for explaining the action. DESCRIPTION OF SYMBOLS 1...Vacuum container, 1a...Duct, 2...Support stand, 2a...Insulator, 3...Silicon block as a material, 4...Electricity member, 5...Gripping member, 6...Electric insulating plate, 7... Lifting mechanism, 7
a... Knob, 7b... Rod, 8, 9... Electric wire constituting electrical wiring, 10... Contact portion between silicon block and current-carrying member, 11... Annular nozzle, 1
2...Working gas supply path, 12a...Insulator, 13...Opening/closing valve, 14...Working gas supply pipe,
15...Opening/closing valve, 16...Exhaust pipe, G...Gas supply means, P...Vacuum pump.

Claims (1)

[Claims] 1. In a vacuum vessel into which a working gas at a required pressure is introduced, high-temperature heating is achieved by bringing a current-carrying member made of carbon or the carbide into contact with a material made of silicon, titanium, etc. or a carbide thereof and energizing it. A method for producing ultrafine powder of a carbide such as silicon or titanium by reaction, wherein the working gas is a compound containing a carbon component. 2. Equipped with a vacuum container into which a working gas of a required pressure consisting of a compound containing a carbon component is introduced, and in this vacuum container, ultrafine powder of carbides such as silicon, titanium, etc. is produced from materials of silicon, titanium, etc. or their carbides. In order to do so, a support base capable of supporting the same material, a gripping member capable of grasping a current-carrying member made of carbon, silicon, titanium, or other carbide so as to be able to contact the above-mentioned material on the support base, and a power-conducting member capable of holding the above-mentioned material and the current-carrying member. is provided with electric wiring that can be energized through those contact portions and the support base, and an elevating mechanism that can hold the energizing member in contact with the material, and supplying the working gas so as to surround the material. The gas supply means includes an annular nozzle formed on the support base and capable of ejecting a working gas so as to surround the material, and a working gas supplying means for supplying the working gas from a working gas supply source to the annular nozzle. 1. An apparatus for producing ultrafine carbide powder, comprising: a working gas supply path bored in the support base to supply a working gas. 3. The apparatus for producing ultrafine carbide powder according to claim 2, wherein the support base is made of a carbon material.