JPS5945915A - Preparation of beta-type silicon carbide powder - Google Patents

Abstract

PURPOSE:To prepare beta-type SiC powder in high yield, by reacting a powdery mixture of SiO powder, C powder and metallic silicon powder in Ar atmosphere, and heating the resultant SiC in an oxidizing atmosphere. CONSTITUTION:Powdery SiO having an average particle diameter of <=1mum is mixed with C powder having an average particle diameter of <=1mum and metallic silicon powder having an average particle diameter of <=10mum at a weight ratio of 1:(0.2-2.0):(0.01-1.0), and the obtained powdery mixture is thermally reacted at 600-700 deg.C in an oxidizing atmosphere to remove the residual carbon. A high-quality beta-type SiC powder suitable for the preparation of a sintered SiC product required to have high strength at high temperature, can be prepared by this process in high yield.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an improvement in a method for producing β-type silicon carbide powder.

[Technical background of the invention and its problems]

For example, sintered bodies of silicon carbide-boron system (8iC-B system) or silicon carbide-magnesium oxide system (5ic-MgO system) are difficult to mechanically compel (and have excellent heat resistance), so Attempts have been made to eject into gas turbine components.These sintered bodies (f) are used as high-temperature geostress materials in practical use. and 1g compatibility is required. In particular, the thermal and mechanical characteristics, which are important factors in chess, are
6* It is desirable to use a raw material that contains a large amount of β-type powder for silicon carbide.

By the way, tit is a method for synthesizing silicon carbide powder.

Conventionally, the following methods are known.

■　Method of completely carbonizing metal silicon powder.

Sl+C-+SIC ■ Gas-phase reaction method using Shikyoushi silica, methyl chloride, charcoal, ice water, and water as raw materials.

S 1C24+ CrnHn 10H2→S IC+HC
LCH, 581Ct5-)-CmHn +H2-+ S
ic -1-HC6 ■ A method in which silica (sio2) is reacted in an argon atmosphere at a reaction stoichiometric ratio.

S 102 + 2 C-+ S iC+ CO2 However, since the carbonization of the upper ddq method fsI is % heat reaction ratio, its! It is necessary to take some measures in order to heat and heat, for example, relatively coarse grains are selected as St, and after carbonization, they are finely pulverized. As a result, the contamination of impurities during this pulverization process is unavoidable, and although there is no problem in using it as a general heat-resistant material such as refractory brick, it is not suitable for applications such as high-temperature gas turbines. In addition, in the method (2) above, for example, surface waves of a semiconductor device 1. However, it cannot be said to be useful for inorganic heat-resistant materials and is not suitable for industrial manufacturing. Furthermore, while the above method (■) has the advantage of not incurring the complexity of reaction operations,
, α-type 810% 5102, etc. have a drawback that the yield of β-type SiC is low.

[Purpose of the invention]

The present invention aims to provide a method that can produce fine β-type silicon carbide powder with good yield.

[Summary of the Invention] The present invention provides silicon monoxide powder l, carbon powder, carbon powder 0.2 to 2.0 and metal silicon powder 0.01 to 1.
The percentage indicates that a mixed powder having a ratio of 0 is subjected to a heat reaction in an argon atmosphere to completely produce silicon carbide, and then heat-treated in a European atmosphere.

The layer weight that limits the blending ratio of the mixed powder, which is the first principle in the invention, is as follows. That is, 8101 9C
If C is less than 2, the product layer other than β-type silicon carbide will increase, and the yield of the silicon carbide will decrease.
．． If it exceeds 0', i, not only will carn's deer be less susceptible to factory rats, but the purity of β-type silicon carbide will lead to a decrease in car collection.

On the other hand, when the old ratio i (less than 1,01) is used for 5101, the 11 ζ rate of β-type silicon carbide decreases by 1. β-type silicon carbide powder with a thickness of less than 1 μm was obtained.
This leads to the contamination of fc and other substances which require a grinding process.

These JO% 0% $1 milling particles are 99% or higher, which is preferable, and the particle size is SI
It is preferable that O and C have an average particle size of 1 μm+l+ or less, and that Si has an average particle size of 10 μm or less.

In the present invention, the temperature condition at 16:00 is 1350~1
It is desirable that the temperature be within the range of 480°C. This is because if this layer weight exceeds the above temperature range, other by-products will be observed, making it difficult to obtain β-type silicon carbide powder suitable for the desired high-temperature, high-stress material.

The purpose of the heat treatment in an oxidizing atmosphere during the heating reaction cooking in the present invention is to remove residual carbon.

The temperature IW of this heat treatment is preferably in the range of 600 to 700°C. If this temperature is lower than 600℃, residual carbon cannot be removed sufficiently, and even
This is because if the temperature exceeds 0°C, the β-type silicon carbide powder will be oxidized.

According to the method of the present invention, an excess of C far exceeding the reaction stoichiometric ratio during the reduction and carbonization reaction is added to SIO, and a predetermined amount of 81 is allowed to coexist.
The reduction of St is promoted, and the carbonization of St is also yen? As the process progresses to M, the total yield of β-type SiC powder is large, and the overall yield of β-type SiC powder is suitable for producing SIC-based sintered bodies that require high thermal stress properties. . Such β-type SI
The reason why C-based powder is obtained is considered to be due to the following mechanism.

That is, the reaction becomes relatively faster as the C/SiO ratio decreases, and 810 is C,! :Reacts to Taniman. In this reaction, 810 and C can exist in a gaseous state, so the proportion occupied by C vapor influences the reduction and carbonization reactions. However, in this case C rat responds 11i tm! Many products other than t and 1s1c are observed in the m phase ratio or in slight excess, but since Clit is in large excess compared to the reaction stoichiometric ratio, β
Type SIC can be easily generated. The excessive presence of C facilitates the formation of β-type SIC, but on the other hand, t, rsi
It causes the mixture of oxides other than cSIC, and is relatively β-type SIC.
The contained fit is lowered. Therefore, in non-invention, the predetermined welfare 81 is made to coexist. By this process, part of the Sl powder is carbonized, but 1. filtration SIO powder surface coating film
6 makes it easier to generate SIO steam, and the 5IO-)
Formation of β-type silicon carbide by -C'? i: It is thought that this makes it easier to produce the desired fine β-type silicon carbide, dramatically improving the production yield of the desired fine β-type silicon carbide, and preventing the contamination of by-products other than SIC.

[Example of actual invention]

Misuichishi υ1-14 sio @ powder with an average particle size of 15 μm, C with an average particle size of 30 μm
The powder and another powder having an average particle size of 2.0 μm were mixed in the proportions shown in the Hr2 table below to prepare 14 kinds of mixed powders 20. Next, these mixed powders were heated and carbonized in an Arl atmosphere under the conditions shown in the same table, and then heat-treated in air at a temperature of 700° C. for 8 hours to obtain SIC-based rice flour powder.

Average grain tW1β type SIC of each SiC-based powder obtained
The content of metal impurities such as 81 (weight %) confirmed by X-ray diffraction was determined.

The results are listed in the same table. In addition, Comparative Examples 1 to 6 are also listed in the table.

〔Effect of the invention〕

As explained in detail above, 1, 4: According to 'RB Ming, it is possible to use sieves without complicated operations or equipment d.
It has remarkable effects such as being able to obtain β-type SiC powder with a high sieve yield that is suitable for producing IC-based sintered bodies.

Claims (1)

[Claims] MU ratio of silicon monoxide powder 1, car d? powder 0.2～
2.0 and metal silicon powder at a ratio of 001 to 1.0 is subjected to a heating reaction in an argon atmosphere to produce silicon carbide, and then heat treatment is performed in an atmosphere with oxidation properties. A method for producing β-type silicon carbide powder.