JPS61215210A - Production of silicon carbide powder - Google Patents

Abstract

PURPOSE:To produce fine powder of silicon carbide sinterable at a normal temperature, by fluidizing metallic silicon powder with a mixed gas composed of hydrogen, hydrocarbon and hydrogen sulfide in a fluidized particle reaction furnace heated at a specific high temperature. CONSTITUTION:A fluidized particle reaction furnace 2 furnished with a perforated plate 1 having gas blasting holes 1a at the bottom of the furnace is heated at a high temperature above 1,200 deg.C and below the melting point of metallic silicon. Metallic silicon powder is charged to the furnace 2 and fluidized by supplying a mixed gas composed of hydrogen, hydrocarbon and hydrogen sulfide through the above blasting holes 1a. A chemical reaction takes place by this process to form silicon carbide powders.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing silicon carbide powder, and in detail,
The present invention relates to a method for producing silicon carbide powder for producing a ceramic member that can be used as a heat-resistant member particularly required for heat resistance in diesel engines, gas turbine engines, and the like.

[Conventional technology]

Conventionally, methods for producing silicon carbide powder for producing sintered ceramic members include: ■ Using fine powder of metallic silicon and carbon powder, Si+C=
A method of producing silicon carbide powder by a chemical reaction as indicated by β-5iC.

■ Using silicon oxide powder and carbon powder, SiO+2C-
β-3i c+c.

A method of producing silicon carbide 1 powder by a chemical reaction as shown by SiO,+3Cwβ(α)-3iC+2GO.

This method is generally adopted as the current industrial method for manufacturing silicon carbide, in which a mixture of carbon powder and silicon material is loaded into an Acheson-type direct current resistance furnace and heated by direct current. This is what is being done.

■ A method for producing silicon carbide powder by reducing silicon oxide (silica) in a mixed gas of hydrocarbon gas and hydrogen to produce silicon carbide and then pulverizing it (JP-A-56-7361)
No. 5).

(2) A method for producing silicon carbide powder by thermally decomposing organic silicon compounds such as SiH4 and S i (CH3) l C'.

(2) A method for producing silicon carbide powder by a gas phase reaction using stcg, hydrogen, and hydrocarbon gas.

etc. are being implemented.

[Problem that the invention seeks to solve]

In view of the current state of the conventional technology as described above, the problem to be solved by the present invention is that in the conventional method for manufacturing silicon carbide powder as described above, in method (2), silicon carbide powder is Although the yield is excellent, there are problems in that it is difficult to produce fine powder of metallic silicon and it is difficult to remove unreacted St mixed in the produced silicon carbide powder.

In method (2), first, when SiO is used, the yield of silicon carbide powder during production is excellent, and it is easy to secure fine silicon carbide powder;
Since iO is extremely expensive, the produced silicon carbide powder is also extremely expensive.

In addition, when using Sin, the operating rate of the reaction furnace is low and productivity is extremely poor, and 190
Since the reaction only progresses at a high temperature of about 0°C, it not only has the drawback that the silica evaporates as Sin, resulting in poor yields, but also because it is a solid phase reaction between carbon powder and silica powder, and moreover, it cannot be carried out at high temperatures. Since the surface of the silica is melted, the surface area becomes smaller and the activity is lowered, which also has the disadvantage that the reaction treatment takes a long time.

In addition, there is a problem in that it is difficult to remove unreacted Sin and carbon mixed in the produced silicon carbide powder.

In method (2), the reaction temperature is 1200 to 1600°C.
There is a problem that not only is it necessary to use a high temperature, but also that silicon carbide powder cannot be directly produced.

In methods ① and ②, the raw material SiH4+
Since both Si (CHI')3CI1 and 5tcI14 are extremely expensive, there is a problem that not only the produced silicon carbide powder is also extremely expensive, but also the yield of silicon carbide powder is poor.

Therefore, the technical problem of the present invention is to chemically react silicon metal powder and carbon source gas in a gas phase state by a gas phase reaction, and then convert the generated silicon carbide powder into a fine powder that can be sintered at room temperature. The object of the present invention is to make it possible to produce silicon carbide fine powder, which can be suitably used as a raw material for structural ceramic materials, at low cost and in high yield.

[Means for solving problems]

In view of these problems in the conventional technology, the present invention has a means to solve the problems in the conventional technology by charging metal silicon powder and heating it to a temperature of 1200°C or higher, but not exceeding the melting point of metal silicon. The metal silicon powder is fluidized by feeding a mixed gas consisting of hydrogen, hydrocarbon gas, and hydrogen sulfide from the gas outlet of a perforated plate provided at the bottom in a fluidized particle reactor heated and maintained at a high temperature. The method of producing silicon carbide powder is characterized in that silicon carbide powder is produced by a chemical reaction between the mixed gas and metal silicon powder.

[Effect]

Hereinafter, the effects of the present invention will be explained.

In the method of the present invention, a mixed gas consisting of metal silicon powder in a fluidized particle reactor and hydrogen, hydrocarbon gas, and hydrogen sulfide blown out from a gas outlet of a perforated plate disposed at the bottom of the fluidized particle reactor is used. The reason why the metal silicon powder is made to flow is to ensure sufficient contact between the metal silicon powder and the above-mentioned mixed gas to promote the β-3iC production reaction.

In addition, in the method of the present invention, the reaction temperature of the metallic silicon powder and a mixed gas consisting of hydrogen, hydrocarbon gas, and hydrogen sulfide in the fluidized particle reactor is set to a temperature of 1200°C or higher but not exceeding the melting point of metallic silicon. The reason for this is that at high temperatures exceeding 1410°C, which is the melting point of metallic silicon, metallic silicon powder melts and is not suitable for the production reaction of β-SiC.
This is because the production reaction rate of β-3iC becomes slow at a low temperature of less than 1200°C.

In addition, as the hydrocarbon gas used in the method of the present invention, propylene, methane, propane, benzene, etc. are usually used, but their concentration depends on the temperature, and is 6% at 1200°C and 18% at 1400°C. It is desirable that the

If the concentration is higher than the above concentration, unreacted carbon will be mixed into the generated silicon carbide powder, and if the concentration is lower than the above concentration, β-3i
This is because the C production reaction does not proceed sufficiently.

Note that it is desirable that the concentration of hydrogen sulfide be between about the same concentration as the hydrocarbon gas and about 2/3 of the amount of the hydrocarbon gas.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

First, metal silicon powder having an average particle diameter of 5.5 μm was subjected to transfer granulation to obtain metal silicon spherical particles 3 having an average diameter of 0.2 to 0.5 m.

Next, the metal silicon spherical particles 3 formed as described above were placed in a vertical fluidized particle reactor 2 in which a perforated plate 1 having a large number of gas outlets 1a having a hole diameter of 0.1 m at intervals of about 3 mm was disposed at the bottom. (100 g was charged into a sintered silicon carbide body having dimensions of 80 m+ in diameter and 400 m in height).

Thereafter, as shown in FIG. 1, at temperatures below 1100°C, only hydrogen is supplied to flow the metal silicon spherical particles 3, and at temperatures above that temperature, hydrogen sulfide and hydrocarbon gas are added to the hydrogen. As shown in FIG. 2, the metal silicon spherical particles 3 were caused to react while flowing, and the product, which became β-3iC, was collected from the outlet of the fluidized particle reactor 2 on an air stream.

That is, 1380°C, propylene concentration 10%.

Using a mixed gas containing 8.5% hydrogen sulfide and the remainder hydrogen, the metal silicon spherical particles 3 are made to flow as shown in FIG. 2, so that Si+2HzS=SiS2+2Hz.

3StS 2 +CzHs+3H2=3SiC+H2
The fluidized particle reactor 2 is formed by a chemical reaction as shown in S.
The product collected by airflow from the top of the tube was β-3iC fine powder 5 with an average particle size of 0.05μ.The maximum particle size of the generated β-3iC fine powder 5 was determined by observation. It was 0.08μ in the range where

Next, β-
0.5% by weight of amorphous boron powder and 0.8% by weight of carbon black were added to a fine powder of silicon carbide made of 5iC, and the mixture was compacted under a hydrostatic pressure of 3 ton/cm 2 .

The silicon carbide molded body compacted in this way was sintered at 2060 t in a He gas atmosphere at 1 atmosphere.

The density of the silicon carbide sintered body produced in this way reached a high density of 96.6% compared to the true density, and the
The average bending strength at room temperature using a test piece with a size of 5 m was 83 Kg/mm''.

〔Effect of the invention〕

As is clear from the above, according to the method for producing silicon carbide powder according to the present invention, silicon carbide powder is produced by chemically reacting a metal silicon powder and a carbon source gas in a gas phase through a gas phase reaction. As a fine powder that can be sintered at room temperature, silicon carbide fine powder can be suitably used as a raw material for structural ceramic materials, and can be produced at low cost and in high yield. There are advantages.

In particular, by employing a chemical reaction form in which volatile silicon sulfide is produced as a reaction intermediate, fine powder could be efficiently produced in the gas phase.

By the way, the sulfide of metal silicon is S　i　S.

SiS is known, and the melting point of Sin is 1090℃
, the boiling point is 1130°C.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the flow state of metal silicon spherical particles while hydrogen is being supplied from the gas outlet of the porous plate. FIG. 2 is a diagram showing the flow state of metal silicon spherical particles while a mixed gas is being supplied from the gas outlet of the porous plate. 1-...-perforated plate. la・------Gas outlet. 2.--.--Fluidized particle reactor (reaction tube). 3--- Monometallic silicon spherical particles. 4------Bullet flow guide board. 5-------The produced fine powder of β-3iC. Applicant: Toyota Motor Corporation Figure 1 Figure 2

Claims (1)

[Claims] 1. In a fluidized particle reactor charged with metal silicon powder and heated and maintained at a high temperature of 1200°C or higher but not exceeding the melting point of metal silicon, hydrogen is released from the gas outlet of a perforated plate located at the bottom. , the metal silicon powder is made to flow by feeding a mixed gas consisting of hydrocarbon gas and hydrogen sulfide, and silicon carbide powder is produced by a chemical reaction between the mixed gas and the metal silicon powder. Method for manufacturing silicon powder.