Chemistry of inorganic compounds – Silicon or compound thereof – Binary compound
Patent
1981-08-05
1983-01-11
Peters, G.
Chemistry of inorganic compounds
Silicon or compound thereof
Binary compound
C01B 3136
Patent
active
043681816
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of producing .beta.-silicon carbide at a temperature of not higher than 1,650.degree. C., wherein carbonaceous powder having a particle size of not larger than 60 .mu.m and silica powder having a particle size of not larger than 150 .mu.m are used, and silicon monoxide, which is formed by a reaction of a mixture of carbon and silica (hereinafter, this mixture is merely referred to as "mixture"), is prevented from escaping from the reaction system, captured and further reacted with carbon.
BACKGROUND ART
Recently, .beta.-silicon carbide has been widely used as filler and binder for refractory, deoxidizer in metallurgy, abrasive for polishing, pigment for high-temperature use and raw material for sintering due to its excellent chemical and physical properties over .alpha.-silicon carbide.
A method of producing .beta.-silicon carbide is lately disclosed in Japanese Patent Laid Open Application No. 160,200/75 entitled as "Silicon carbide powder for sintering and a method of producing the same". In this method, .beta.-silicon carbide is produced by a gaseous phase reaction by means of a particular apparatus. However, raw materials adapted to be used in the gaseous phase reaction are relatively expensive and easily hydrolyzed in air, and the yield of .beta.-silicon carbide in the gaseous phase reaction is generally low, and hence the products are always expensive, and the production of .beta.-silicon carbide by the gaseous phase reaction is disadvantageous.
Further, a method of producing .beta.-silicon carbide inexpensively in a large scale is disclosed in Japanese Patent Laid Open Application No. 142,697/77 entitled as "Continuous method of producing .beta.-silicon carbide". In this method, since raw material silica consisting of relatively large particles having an average particle size of 3-10 mm is used, the reaction rate is very low at a temperature of not higher than 1,650.degree. C., and therefore a very high temperature of higher than the melting point (about 1,710.degree. C.) of silica is required in the commercial production of .beta.-silicon carbide. Moreover, in order to prevent sticking of raw material mixture by silicon monoxide formed during the reaction, unreacted silica and carbon must be intentionally left in the reaction product, and therefore the yield of .beta.-silicon carbide is low and a superfluous operation must be carried out in order to remove these unreacted silica and carbon.
The present invention aims to obviate these drawbacks. That is, in the present invention, silica having a particle size of not larger than 150 .mu.m is used in order to complete a major part of reaction at a relatively low temperature of not higher than 1,650.degree. C., and further silicon monoxide formed during the reaction is prevented from escaping from the reaction system, and the captured silicon monoxide is again contacted with unreacted carbon at reaction temperature, whereby .beta.-silicon carbide is produced in a sufficiently high efficiency.
DISCLOSURE OF THE INVENTION
The feature and effect of the present invention will be explained in more detail hereinafter.
A reaction for forming silicon carbide (SiC) from silica (SiO.sub.2) and carbon (C) is generally shown by the following formula (1), and .beta.-silicon carbide is formed within the temperature range defined in the present invention.
The reaction shown by the formula (1) proceeds through a process, wherein silica is firstly reacted with carbon to form silicon monoxide (SiO) through the reaction shown by the formula (2), and the silicon monoxide (SiO) is reacted with ambient carbon to form .beta.-silicon carbide as shown by the formula (3). The fact that .beta.-silicon carbide is mainly formed through a main reaction represented by the formulae (2) and (3) has been ascertained by the experiment of the inventors as well. represented by the formulae (4) and (5). In both cases, silicon monoxide has an important role in the production of .beta.-silicon carbide.
In the reaction represent
REFERENCES:
patent: 3368871 (1968-02-01), O'Connor et al.
patent: 4162167 (1979-07-01), Enomoto et al.
patent: 4226841 (1980-10-01), Komeya et al.
Hase Teizo
Suzuki Hiroshige
Peters G.
Suzuki Hiroshige
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