JPS63201010A - Production of hyperfine silicon carbide powder - Google Patents

Abstract

PURPOSE:To produce a powder mixture suitable for powdery raw material for powder metallurgy, etc., and consisting of hyperfine silicon carbide powder having high purity and carbon powder without requiring a crushing stage by carrying out a gaseous phase thermal decomposition reaction of hexamethyl disilane at high temp. above a specified temp. CONSTITUTION:A furnace core pipe 2 is inserted into a horizontal electric furnace 1, and heated with a heating coil 3. Carrier gas (e.g. H2) contg. hexamethyl disilane is introduced from one end of the pipe 2, and the hexamethyl disilane is thermally decomposed at >=800 deg.C in the gaseous phase. By this method, a powder mixture consisting of hyperfine silicon carbide powder of high purity and carbon powder is produced and discharged from another end of the furnace core pipe 2. The obtd. powder mixture is usable in itself for a raw material of powder metallurgy without separating the component. Moreover, the mean particle size of the SiC powder or the proportion of the carbon powder, etc., can be adjusted by controlling the thermal decomposition temp. in the gaseous phase or the proportion of the introduced carrier gas, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for producing a mixed powder consisting of high-purity ultrafine silicon carbide powder and carbon powder suitable for use as a raw material powder for powder metallurgy. It is.

[Conventional technology]

In general, silicon carbide (hereinafter referred to as SiC) powder has excellent wear resistance, oxidation resistance, high temperature strength, and thermal conductivity, and is therefore used in sintered abrasives and sintered materials that require these properties. It is used as a raw material powder in the manufacture of heat-resistant parts and various sintered parts.

As for the manufacturing method of SiC powder, (a) Acheson method, (b) carbon silicification method, (C) thermal decomposition method of polymeric carbosilane%, (d) gas phase reaction method, and (e) organosilicon method. Gas-phase thermal decomposition methods for compounds are known.

[Problem that the invention seeks to solve]

However, method (a) above does not require a high-temperature reaction, but requires a pulverization process, which has the problems of contamination with many impurities and difficulty in pulverization.
The above method (b) is difficult to pulverize and has problems in industrial mass production, and the above method (C) produces SiC in the form of fibers, making it impossible to obtain a fine powder. Since the above method (d) utilizes the reaction between a halogen compound such as 5ICt4 or (CH3)5SiCt and a hydrocarbon, halogen elements remain in the raw powder produced, and high purity powder may not be produced. Furthermore, in the method (d) above, there is a problem that the special S
i compound is used as a raw material, and the bonding ratio of Sl and C is 1.
The purpose of this method is to produce SiC powder with a stoichiometry of .

[Means for solving problems]

Therefore, the present inventors conducted research to solve the problems of the various conventional methods described above, and as a result, using hexamethyldisilane, an organosilicon compound, as a raw material,
When subjected to a gas phase pyrolysis reaction at a temperature of 00°C or higher, SiC powder becomes ultrafine particles with an average particle size of 0.02 to 0.1 μm and has a high purity of 99.9% or higher, and 0.5 to 7 μm. A mixed powder consisting of carbon powder containing % by weight is obtained,
This mixed powder is made into ultra-fine particles with high purity as described above.
Since it is composed of iC powder and carbon powder, it was found that it can be used as a raw material for powder metallurgy without the need for a pulverization process or the addition of carbon powder.

This invention was made based on the above knowledge, and uses hexamethyldisilane ((CH3)6Si2), which is an organosilicon compound, as a raw material, and heats it at 800°C.
This method is characterized by producing a mixed powder of high-purity ultrafine SiC powder and carbon powder through a gas phase pyrolysis reaction at the above temperature.

In addition, in the method of this invention, the gas phase pyrolysis reaction temperature is 80
If the temperature is lower than 0°C, the yield of high-purity ultrafine SiC powder will decrease, but the reaction is slow and unsuitable for industrial use.
It was determined that

〔Example〕

Next, the method of the present invention will be specifically explained using examples.

Example 1 In a horizontal electric furnace 1 shown in a schematic explanatory diagram in FIG.
Inner diameter of this component: 30m x length: 600m
A with dimensions of! The temperature at the center of the 203 furnace core tube 2 is heated and maintained at the temperature shown in Table 1 using the heating coil 3, and N2 containing 1 g of hexamethyldisilane is poured into the furnace core tube 2 from one end. The hexamethyldisilane was charged with a carrier gas in the proportion shown in Table 1, and the hexamethyldisilane was subjected to a gas phase thermal decomposition reaction for the reaction time shown in Table 1, and the reaction product was removed from one end. out,
The present invention method 1 is carried out by collecting the mixed powder with a collector.
- 6 were carried out, respectively.

The properties of the resulting mixed powder were measured using X-ray diffraction and a transmission electron microscope, and the measurement results are shown in Table 1.

Example 2 This was carried out using the apparatus shown in a schematic explanatory diagram in FIG.

That is, after evacuating the inside of the cylindrical reaction vessel 4 with an inner diameter of 60011 mm and a height of 1000 mm to a pressure of 10-' torr, an Ar gas inlet was opened to maintain the inside of the reaction vessel at a reduced pressure of about 200 to 300 torr. Ar gas is introduced from 5, and in this state, the high frequency power source 6 is supplied with a frequency of 1.
3.56 MHz, 30 KVA output, high frequency power is applied to ignite Ar plasma, and at the same time as ignition, N
2. N2 gas is introduced from the gas introduction lower to adjust the inside of the reaction vessel to 1 atmosphere, and at the same time, to stabilize the high frequency plasma 8, hexamethyldisilane is used as a carrier gas, and a mixed gas of Ar and N2 is used as a carrier gas. , hexamethyldisilane: 0.79/r, Ar: 5 L/r#L,
N2: High frequency plasma at a rate of 3 L/mjtc 8
The tail portion (estimated temperature of about 2800°C) 9 is introduced to cause a gas phase pyrolysis reaction, and this reaction is carried out for 10 minutes.Meanwhile, the product is cooled on a cooling table (circulated water cooling) 10 and mixed in a collector 11. Method 6 of the invention was carried out by collecting the powder.

The properties of the resulting mixed powder were measured in the same manner, and the first
Shown in the table.

〔Effect of the invention〕

As is clear from the results shown in Table 1, the method 1 of the present invention
All of the mixed powders manufactured by 6 to 99.9
% or more, and the average particle size is 0.02-0.
It is clear that it consists of ultrafine SiC powder of 171 m and carbon powder of 0.5 to 7 weight.

In addition, in the method of the present invention, by controlling the gas phase pyrolysis temperature, carrier gas introduction ratio, etc.
It is possible to freely adjust the average particle size and yield of iC powder, as well as the proportion of carbon powder.

As described above, according to the method of the present invention, a mixed powder consisting of high-purity ultra-fine SiC powder and carbon powder can be produced without the need for a pulverization step, and the high-purity ultra-fine SiC powder is It may be used alone in a state separated from carbon powder, but it is more desirable to use it in the form of the above-mentioned mixed powder as a raw material for powder metallurgy, as industrially useful effects can be obtained.

[Brief explanation of the drawing]

Both FIG. 1 and FIG. 2 are schematic explanatory diagrams showing an apparatus for implementing the present invention. 1...Electric furnace% 2...Furnace core tube, 3...
Heating coil, 4... Reaction vessel, 5... Ar gas inlet, 6... High frequency power supply, 7... N2 gas inlet, 8... High frequency plasma, 9... Hexamethyldisilane introduction The tail portion of the high-frequency plasma, which is the position, 10...Cooling table, 11...Collector.

Claims (1)

[Claims] Using hexamethyldisilane, an organosilicon compound, as a raw material, a mixed powder consisting of high-purity ultrafine silicon carbide powder and carbon powder is produced by subjecting it to a gas phase pyrolysis reaction at a temperature of 800°C or higher. Characteristic method for producing ultra-fine silicon carbide powder.