JPS61178413A - Production of silicon carbide powder - Google Patents

Abstract

PURPOSE:To produce easily finely divided powder of silicon carbide, by constituting a process to oxidize metallic silicon powder in an oxidizing atmosphere to form ultrafine particulate or gaseous silicon monoxide and a process to carbonize the silicon monoxide in a reducing atmosphere containing carbon. CONSTITUTION:The valves 24 and 25 of the oxygen feed pipe 22 and the LPG feed pipe 23 are opened, the burner 20 is ignited, the reaction furnace 10 is sufficiently dried and deoxidized. Then, metallic silicon powder is continuously fed to the furnace 10 by the feeder 21, and simultaneously oxygen in an amount equivalent to the reaction of the metallic silicon powder is fed from the oxygen feed pipe 22. Then, the valve 13 of the methane gas feed pipe 12, and a methane gas heated to about 1,000 deg.C by the preheating furnace 11 is fed to the reaction furnace. In this operation, the reaction flame 26 is continuously formed on the front of the burner 20 by oxidation of the metallic silicon powder, silicon carbide which is provided with the heat energy of the reaction flame, reduced with methane gas, and carbonized is collected by the powder collector 31 and the bag filter 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing finely powdered silicon carbide.

[Prior Art] Silicon carbide is used in various fields due to its excellent thermal shock resistance. In addition, when using it, it is desirable that the particle size of the raw material particles be 1000 Å or less in terms of ease of sinterability at low temperatures and increase in catalytic activity. Silicon carbide powder was desired.

Conventionally, in manufacturing silicon carbide powder, (1)
There is a method of producing silicon carbide by reacting silicon dioxide with carbon as shown in the formula.

Si 02 +30-+Si C+2CO...
(1) There is also a method of producing silicon carbide by reacting silicon tetrachloride with methane as shown in formula (2).

Si Cl 4+CH4→Si C+4HC1・
(2) [Problems to be solved by the invention] The above-mentioned method had the following problems.

In the method of formula (1), in carrying out the reaction, 2
A temperature exceeding 1,000°C was required, and a large amount of thermal energy was required. In addition, the obtained silicon carbide has a large particle size, so a pulverization process is indispensable to obtain fine powder silicon carbide.As a result, the particle size distribution of the obtained powder silicon carbide is wide. In addition, it was quite difficult to obtain fine particles of 1000A or less.Furthermore, impurities were sometimes mixed in during the pulverization process.And because there were many manufacturing steps, the product became expensive. There was also.

Furthermore, in the manufacturing method of formula (2), silicon tetrachloride, which is a raw material, is expensive, and thus the silicon carbide obtained is also expensive. There is also the problem that harmful hydrogen chloride gas is generated, and its treatment requires a lot of man-hours.

The present invention has been made in view of the above-mentioned problems, and provides a manufacturing method for easily obtaining fine particulate silicon carbide powder.

[Means for Solving the Problems] The production method of the present invention includes an oxidation step in which metallic silicon powder is oxidized in an oxidizing gas atmosphere to form ultrafine particulate or gaseous silicon monoxide; and cough silicon monoxide. and a carbonization step of carbonizing in a reducing gas atmosphere containing carbon.

The oxidation step referred to in the present invention is one of the features of the present invention, and is a step in which metallic silicon powder is oxidized in an oxidizing gas atmosphere to form silicon monoxide.

It is preferable that this metal silicon powder has fine particles, and 2
00 mesh or less is particularly desirable.

If a metal silicon powder having such particles is used, the particle size of the obtained silicon carbide powder will also be in a preferable range of 100 to 1.000 particles. In addition, the purity of metallic silicon powder is particularly high.
There is no need to use anything else.

Typical oxidizing gases include oxygen gas, ozone gas, etc., and those that oxidize metal silicon powder to form silicon monoxide can be used. Various methods can be considered for reacting the metal silicon powder and the oxidizing gas, but the metal silicon powder and the oxidizing gas form a dust cloud, and this dust cloud is ignited to cause an explosion. It is desirable to oxidize by burning. According to this method, the heat generated during the oxidation reaction promotes the oxidation of other metal silicon powders, creating a high field and producing ultrafine particulate or gaseous silicon monoxide. Then, it becomes possible to perform the carbonization step described below by utilizing the thermal energy of the reaction flame during oxidation. As this ignition means, a burner, plasma jet, arc discharge, laser light, etc. can be used. Further, it is preferable to determine the optimum concentration of the dust cloud depending on the particle size of the metal silicon powder used, the ignition means, etc. In addition, metallic silicon powder is
It may be supplied intermittently by separating short periods of scratching, or
It may be fed continuously. However, from the standpoint of thermal efficiency, it is desirable to form the reaction flame continuously.

The carbonization step is a step in which the silicon monoxide obtained in the oxidation step is reduced and carbonized to form silicon carbide. As the reducing gas containing carbon used in this carbonization step, a dust cloud such as a mixture of hydrogen gas and carbon can be used, for example. According to this, silicon monoxide can be reduced with hydrogen gas and carbonized with carbon at the same time. However, it is desirable to use a hydrocarbon-based gas such as methane or ethane that has sufficient hydrogen to reduce the silicon monoxide and sufficient carbon to carbonize it.

When this hydrocarbon-based gas is used, a reduction reaction occurs due to the hydrogen and carbon elements contained therein, followed by a carbonization reaction due to the carbon. Note that in order to prevent the reaction system from being cooled by the reducing gas containing carbon, it is desirable to heat the reducing gas containing carbon in advance.

General silicon is reduced and carbonized to silicon carbide by contacting with the above carbon-containing reducing gas at high temperature. In this case, it is desirable that the oxidation step and the carbonization step be performed consecutively in order to utilize the heat of the oxidation step.

When a dust cloud is formed by the metal silicon powder and the oxidizing gas in the oxidation step, a continuous reaction flame containing a large amount of silicon monoxide is formed by the metal silicon powder and the oxidizing gas. Therefore, by generating this continuous reaction flame in the above-mentioned reducing atmosphere, reduction and carbonization reactions proceed continuously due to the thermal energy of this continuous reaction flame, and ultrafine particle or gaseous general silicon is converted into fine powder. It can be made into a form of dicarbide.

The obtained silicon carbide can be collected by a well-known collection device such as a bag filter. Note that since the gas body that has passed through the collection device usually contains unreacted oxidizing gas and reducing gas containing carbon, it is desirable to discharge it after processing such as combustion.

[Operations and Effects of the Invention] According to the manufacturing method of the present invention, by only using an ignition means such as a burner or a plasma jet, the heat generated by the reaction between the metal silicon powder and the oxidizing gas causes the oxidation of other metal silicon powder. Powder reaction is accelerated. Therefore, thermal efficiency is extremely high (and costs can be reduced).

A reaction flame containing ultrafine particle or gaseous generalized silicon is continuously formed, and by contacting this reaction flame with a reducing gas containing carbon, a large amount of fine particle silicon carbide powder is continuously formed. is manufactured. Therefore, the present invention has great effects such as being able to obtain homogeneous silicon carbide powder extremely efficiently and with good mass production.

[Example 1] Fig. 1 shows a manufacturing apparatus related to the manufacturing method of the present invention. This manufacturing apparatus includes a reaction F10 whose inner wall is surrounded by heat-resistant bricks 15 and a discharge passage 30 on one side wall, and a reactor 10.
The burner 20 is provided on the other side wall of the reactor 10 and sends flame to the reactor 10. burner 20
A powder supply device 21 for supplying metal silicon powder, an oxygen supply pipe 22 for supplying oxygen, and an LPG supply pipe 23 for supplying LPG for a pilot flame are disposed in the fuel cell. A methane gas supply pipe 12 for supplying methane gas via the preheating furnace 11 is provided on the upper wall of the reactor 10 so as to open into the reactor 10 .

Further, a powder collection bag W131 is provided in the discharge passage 30,
A bag filter 32 is provided adjacent to the powder collecting device 31 to collect uncollected silicon carbide powder. The exhaust gas that has passed through the bag filter 32 is configured to be discharged outdoors after passing through a combustion processing section 34 by a blower 33.

Using the reaction apparatus configured as described above, the reaction was carried out in the following manner to produce silicon carbide powder.

First, oxygen supply pipe 22 and LPG supply! ! 23 valves 24
．． 25 was opened and the burner 20 was ignited to sufficiently dry the inside of the reactor 10 and deoxidize it.

After that, the powder supply device 21 supplies 1 portion of metal silicon powder.
It was continuously supplied at a supply rate of 0 to 30 kg/hour, and at the same time, oxygen was supplied from the oxygen supply pipe 22 in an amount equal to the reaction equivalent of the metal silicon powder (4 to 12 kg/hour). Then, the valve 13 of the methane gas supply pipe 12 is opened, and the methane gas heated to about 1000°C by the preheating furnace 11 is supplied at 16 to 24 Nm
It was supplied at a flow rate of /hour.

At this time, a reaction flame 26 is continuously formed in front of the burner 20 by the oxidation reaction of the metal silicon powder, and the synthesized silicon carbide powder is synthesized by obtaining thermal energy and being reduced and carbonized by methane gas. and was collected in a bag filter-32 at a yield of 14 to 40 ko/hour.

Furthermore, the exhaust gas that has passed through the bag filter 32 is transferred to the blower 3
After being sent to the combustion processing section 34 by 3 and subjected to combustion processing,
It was discharged outdoors.

When the obtained powder was analyzed by electron microscopy and X-ray diffraction, it was found to be a silicon carbide powder with a particle size distribution between 100 and 1000 particles and a β-type cubic crystal structure.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a manufacturing apparatus according to an embodiment of the present invention. 10... Reaction furnace 12... Methane gas supply pipe 20... Burner 21... Powder supply device 22
...Oxygen supply pipe 23...LPG supply pipe 30...
・Discharge passage 31...Powder collection device patent applicant
Toyota Motor Corporation Representative Patent Attorney Hirotoshi Okawa Patent Attorney Original Code Shudo Patent Attorney Akio Maruyama Figure 1

Claims (6)

[Claims] (1) An oxidation process in which metallic silicon powder is oxidized in an oxidizing gas atmosphere to form ultrafine particulate or gaseous silicon monoxide, and a carbonization process in which the silicon monoxide is carbonized in a reducing gas atmosphere containing carbon. A method for producing silicon carbide powder, comprising: (2) The method for producing silicon carbide powder according to claim 1, wherein the reducing gas containing carbon is a hydrocarbon gas. (3) Production of silicon carbide powder according to claim 1, wherein the oxidation step is performed by forming a dust cloud with metal silicon powder and an oxidizing gas, and igniting the dust cloud to cause it to explode and burn. Method. (4) The method for producing silicon carbide powder according to claim 3, wherein ignition is performed using a burner or a plasma jet. (5) The method for producing silicon carbide powder according to claim 1, wherein the metal silicon powder has a particle size of 200 mesh or less. (6) The method for producing silicon carbide powder according to claim 1, wherein the reducing gas containing carbon is heated in advance and then supplied.