JPS63147811A - Production of fine sic powder - Google Patents

Abstract

PURPOSE:To mass-produce SiC at high yield in a method for heat-treating a mixture of fine SiO powder, material contg. C and SiC powder or its molded article by using ultrafine powder as the above-mentioned fine SiO powder. CONSTITUTION:A mixture consisting of SiO2 powder or SiO2-contg. oxide powder and material contg. C and/or metallic Si powder or its molded article is heat-treated under reduced pressure. SiO powder is obtained from SiO vapor generated in this case by means of vapor phase condensation. Primary particles of SiO powder obtained by such a way are extremely ultrafine powder not more than about 0.1mu. The mixture of this ultrafine SiO powder and material contg. C or its molded article is heat-treated in Ar, H2 or gaseous CO or in a gaseous mixture thereof. By this method, fine and high-purity SiC powder can be mass-produced industrially in high yield.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for producing silicon carbide powder, and in particular to a method for producing silicon carbide powder, which has a high β-5iC content and is fine and uniform in particle size. This is a proposal regarding silicon carbide (SiC) manufacturing technology.

Such silicon carbide (SiC) is a type of ceramics that has excellent functions in terms of high temperature stability, high temperature strength, high thermal conductivity, etc., and can be used as energy materials, chemical equipment, high temperature gas processing/electric heating elements, or; It is used in fields such as air abrasives, and especially when used as a material for high-temperature structures, it is a material that is well suited for the purpose of saving energy and saving resources.

<Prior art> Conventionally, many techniques have already been proposed regarding the industrial use of SiC powder.
In No. 46398, a mixture of SiO , discloses a method for pulverizing and refining this. That is, to explain this method in more detail, the SiC production reaction of the above formula (1) is usually as follows: SiO□-C-'' SiO=Co-
−−−−−−１・−・−、−、、1Qj5i0 ↓
2 C-SiC+ Co Yama-1--
The reaction proceeds through a two-step reaction of -...------...-+31.

In short, this conventional method is based on the S produced in the reaction of equation (2).
In order to make carbon absorb SiQ gas by delaying the generation of iO gas, and to allow the raw material to flow smoothly in the furnace, finely powdered silica stone and carbon are preformed,
This is a technology that heats this and causes it to react.

Furthermore, in JP-A-54-122312, 100 parts by weight of carbon black and 170 to 2 parts by weight of SiO gas
10 parts under reduced pressure of 10n+Hg or less, 1200-15
A method is proposed in which the reaction is carried out at a temperature of 00°C.

Furthermore, in JP-A No. 59-227706, fine carbon powder suspended in non-oxidizing gas and SiO gas were heated to a high temperature.
f A method of reacting at 1500°C or higher is proposed.

<Problems to be Solved by the Invention> However, each of the above-mentioned conventional techniques has the following problems that need to be solved. First, JP-A-52-4
In the method of No. 6398, the S'rC in the obtained SiC clinker sinters with each other, and the SiC in the form of fine powder
In order to obtain this, it is necessary to pulverize for a long time, which is not economical, and the method of JP-A-54-122312 requires complicated operations and is not practical in order to carry out the reaction under reduced pressure and at high temperature.

Furthermore, in the method proposed in JP-A No. 59-227706, S
As a device to obtain SiC by introducing tO gas, equipment for suspending C is used, and the molar ratio of C and SiO is changed in the floating layer.
/SiO'42 is considered to be indispensable, resulting in a disadvantage that the manufacturing equipment becomes complicated.

As a result of intensive research into the problems faced by the above-mentioned prior art, the inventors of the present invention have previously published the patent application No. 60-265080.
The technology disclosed in No. 265081 was developed.

That is, SiO fine powder, carbon-containing material and SiC
We have developed a method in which this mixture or its compact is used as a raw material and heat-treated in a temperature range of 1400 to 2000°C under Ar, )l, CO gas, or a mixture of these gases. According to this method, highly pure and fine SiC powder can be obtained in high yield.

However, in the case of the prior invention filed by the present inventors prior to the present invention, when increasing production, depending on the selection of raw material composition, mixing conditions, heat treatment conditions, etc., SiC powder may contain Si.
There is a further problem to be solved in that O□ may remain and as a result only SiC powder of low purity can be obtained.

As a countermeasure against this problem, there is a conventional technique disclosed in JP-A-59-13616. According to this technique, a mixture of SiO□ and carbon or metal silicon is heat-treated to generate SiO vapor, which is caused by adiabatic expansion. It is said that by producing SiO fine powder and heat-treating the resulting 5ill fine powder in a reducing carbonizing atmosphere such as C1, it is possible to produce N of high purity SiC super fine powder.

However, the conventional manufacturing technology for SiO fine powder, in which SiO vapor is also injected into a reducing nitriding atmosphere or into a reducing nitriding atmosphere by adiabatic expansion, is fine for small-scale production, but when producing large quantities, it requires 5iOz gas. L) The 1-piece pipe that sends the slO becomes clogged with the pseudo-condensed SlO. Moreover, the nozzle for injecting it through adiabatic expansion is eroded by the 5iQ mo'i and no longer functions as a nozzle. In some cases, the reactants accumulate in the nozzle and the nozzle closes, so it cannot be said that this is a manufacturing method that is truly suitable for industrialization and mass production as the present invention aims to achieve.

The present invention aims to overcome these problems faced by the prior art.

Means for Solving the Problems> The inventors of the present invention have conducted intensive research in view of the above-mentioned circumstances, and have found that if a fine SiO powder is used as a raw material, the production amount can be increased. Very fine and high purity SiC
We have found that powder can be obtained in high yield, and based on this knowledge, we have made this invention.

The present invention provides S
Fine SiO powder is collected from iO vapor, and a mixture of this fine SiO powder, carbon-containing material, and SiC'FA powder or a molded product thereof is heated in Ar, t(2, (Q gas) or a mixed gas thereof. This is a method for producing 5iCi powder that undergoes heat treatment.

The unique idea behind the present invention lies in the fact that we traced back to the process of producing SiC powder used as a raw material.
So-called 5in2 powder or mullite (3A 1 z
O* ・2SiO1), wollastonite (CaO-5
Si such as iO□) and zircon (ZrOz・SiO□)
A mixed powder consisting of an oxide powder containing O□ and a carbon-containing material or 22K silicon powder in place of the carbon-containing material, or a molded product thereof, is heat-treated under reduced pressure, and the 5iOi generated at that time is The point is that SiO'FA powder is obtained from air by vapor phase condensation. The thus obtained SiO powder secondary particles are extremely fine ultrafine powders of 0.1 μm (1000 particles) or less.

The second feature is that the SiO ultrafine powder and the carbon-containing material are
The mixing ratio of SiO ultrafine powder and carbon in the carbon-containing material is expressed as a molar ratio (C/5iO), and is mixed so that it is within the range of 1.0 to 3.0, and SiC is used as a seed crystal. A mixed powder containing powders or a molded product thereof is heated by Ar, H
2. Heat treatment in CO gas or a mixed gas thereof (hereinafter abbreviated as Ar gas, etc.).

By adopting such a method, it is possible to stably produce a highly purified and fine S+C powder.

The Si adopted in the present invention, which is the first feature mentioned above,
In the production of ultrafine O powder, ultrafine SiO powder of 0.1 μm or less can be easily obtained without the complicated and difficult manufacturing technology of adiabatic expansion and squirting in the conventional manufacturing method described above. That is, by heat-treating the mixed raw material powder etc. under reduced pressure to generate SiO vapor, and transporting the 5iO7% gas in the gas phase using Ar gas etc., 0.1
Extremely fine SiC powder of micrometers or less can be stably mass-produced.

So-called S i Cyi powder C obtained by the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-13616
Second, in the case of small-scale production, contact with gas can be ensured, and products with a SiC flavor can sometimes be obtained. However, as the production volume increases, there is a shortage of reducing gas and the contact layer with the gas becomes insufficient, resulting in only SiC powder containing a considerable amount of SiO□ produced by the disproportionation reaction of SiQ. There are many things. In this regard, in the present invention, a mixture of fine SiC powder, carbon-containing material, and SiC powder is heat-treated in Ar gas, etc., so that sufficient mixing will prevent insufficient reduction even in mass production. SiO
It is possible to eliminate the interval J that is generated by □.

The SiC powder obtained is also 0.1μ as a raw material.
1 μm as we use very fine SiO crystals with a diameter of less than 1 μm.
It is possible to stably produce fine particles of m or less.

Effect> The conditions employed in the production method of the present invention will be specifically explained below.

First, among the raw materials used in the production method of the present invention, S
Commercially available iO□ powders can be used.

In addition, as an oxide powder containing SiO□, zircon (
ZrOz ・5iOz) Mullite (3A 1 z
Oi '2S10□), wollastonite (Can・Si
Oxide powder containing SiO□ of various cloth plates such as O□) may be used. Toku-2, Zircon (Z r 13□・S
When iO□) powder is used, it is possible to produce high-quality zirconia powder and at the same time obtain ultrafine SiO powder, which is particularly suitable for the present invention.

Next, in the present invention, a carbon-containing material is mixed with the SiO□-based raw material, but petroleum coke, coal pitch, carbon black, various organic resins, etc. may be used as the carbon-containing material for the purpose of the present invention. is achieved.

Further, the same effect can be obtained even if a metal silicon powder is used in place of the carbon-containing material, or even if the carbon-containing material and the metal silicon powder are mixed at the same time.

Next, a method for obtaining 5iOi powder will be explained.

At this stage, the above-mentioned SiO□-based raw material and carbon-containing powder and/or metal silicon powder are thoroughly mixed, the mixed powder is used as it is, or it is made into a compact, and heat-treated under reduced pressure to form 5iOi. to occur. Suitable conditions for reduced pressure heat treatment are 1300 to 2000°C at 0.1 atmosphere or less.
temperature range. As for the atmosphere during the residual heat treatment, it is desirable to use Ar gas, a gas that prevents the oxidation of carbon or gold and silicon in the raw μ mixture. Under these heat treatment conditions, Sing gas is generated, and the SiO ultrafine powder is recovered by vapor phase condensation.

The thus obtained SiO ultrafine powder has a very fine particle size of 0.1 μm or less, and when taken out into the atmosphere, only the surface becomes oxidized.

Next, the present invention mixes a carbon-containing substance and a silicon carbide powder bundle with the SiO fence fine powder obtained as described above,
The mixed powder or its compact is heat treated in Ar gas or the like to obtain a 5iC1i powder. The carbon-containing substance to be mixed with the SiO ultrafine powder is not particularly limited, but may include the following:
The same kind of carbon-containing material mixed with the above-mentioned 5i02-based raw material can be used.

Now, in the present invention, the mixture of SiC powder and carbon in the carbon-containing material has a molar ratio (C/5iO) of 1.0 to 3.0
By blending so as to show the range of , it is expected that the yield of SiC powder will be improved. This is due to the following reason. SiO
: If the amount of C per mol is less than 1.0 mol, Sing formation is observed and the yield of SiC decreases.

On the other hand, if the amount of C exceeds 3.0 mol per mol of Sin, the amount of unreacted free C will increase, resulting in a decrease in the yield of SiC.

In the present invention, SiC powder is further mixed with the SiC powder and C-containing material, and the purpose of this is to increase the yield of SiC powder. As the raw material SiC powder to be used, β-5iC powder with high purity and small particle size is preferable.
For 100 parts by weight of the total weight of powder and CAE-based material,
The range is preferably from 0.1 to 100 parts by weight, because if the amount of SiC powder is less than 0.1 parts by weight, a small amount of SiO□ will be produced, and as a result, the amount of SiC powder produced will be reduced. Decrease. On the other hand, if the amount is more than 100 parts by weight, more than necessary will be added, making it uneconomical.

In the present invention, a mixed powder of the above-mentioned 5iOi powder, C-containing material, and SiC powder is used, but the mixed powder may be used as it is, or the mixed powder may be molded into a molded product using a molding machine or the like. In the case of a molded product, it is desirable to have a molded product density of 1.5 g/ali or less. If it exceeds 1.5 g/cal, some SiO□ may be generated in the product and the yield of SiC may decrease. The reduction carbonization reaction of SiO proceeds easily and is suitable for obtaining fine powder of SiC at a high yield.

Next, the mixed powder of the SiC powder, the C-containing material, and the SiC powder or the raw material for the compact is heated and fired in an atmosphere filled with Ar gas or the like.

The gas atmosphere is preferably Ar, J, CO, He gas, or a mixed gas atmosphere thereof.

The heating and firing temperature is preferably in the range of 1400 to 2000°C. At temperatures below 1400°C, it is difficult to generate SiC, and conversely, SiO□, etc. are likely to be produced, and at temperatures above 2000°C, sintering of the resulting powder occurs, making it impossible to obtain fine SiC. range.

In the present invention, if the blending ratio (C/5iO) of the raw materials is large, barley may remain after firing. In such a case, the fired carbon can be further removed by burning it in an oxidizing atmosphere. The firing temperature in an oxidizing atmosphere is preferably 700° C. or lower.

In addition, by adopting the method of the present invention, the reaction to generate SiC from SiO occurs within the mixture or the molded body.
As a reactor, it is only necessary to use a furnace whose atmosphere can be adjusted, and fine SiC powder can be obtained using a very simple furnace.

<Examples> Examples of the present invention will be described below along with descriptions of comparative examples.

(1) SiO production (Table 1) Approximately 10 kg of mixed molded bodies prepared from various mixed powders consisting of SiO2-based oxides and reducing agents shown in Table 1 were used in a vacuum furnace under the reduced pressure conditions also shown in Table 1. Heat treatment is performed to generate SiO vapor, and then S
An iO ultrafine powder was obtained, and this ultrafine powder was collected using a bald filter. The amount of SiO ultrafine powder obtained varied within the range of 2 to 7 k+r depending on the type of original 14 mixture.

FIG. 1 shows an example of an S electron micrograph of the 5iOi powder obtained by the above method. As is clear from FIG. 1, most of the powder was extremely fine particles of about 100 to 300 particles. Regarding this, when the ocher powder is fired in the atmosphere, it changes to a pure white powder, and the weight increase at that time and the infrared absorption spectrum of the pure white powder were measured. The ultrafine powder was confirmed to be SiO powder since it gave an absorption spectrum exactly the same as that of crystalline silica. Also, the first
All of the powders obtained from each heel raw material force 1 in the table were powders that were almost equivalent to those shown in the electron microscopy photograph in Figure 1, so for the synthesis of the following SiC powder, the method in Table 1 was used. The SiO powder obtained in step 5 was used.

(2) SiC production Mixed compacts weighing approximately 1 kg each were prepared from a mixed powder of 5ill powder, carbon black, etc. at the mixing ratio shown in Table 2, and heat-treated at 1600° C. in Ar gas.

Regarding the product obtained through this heat treatment, the identification results by powder X-ray diffraction, SiC formation, and the 50% average particle size were determined and are shown in Table 2.

In addition, as Comparative Example 3, the same SiO powder obtained by the method shown in JP-A-59-13616 was heated at 1400°C.

Table 2 also shows the results of heat treatment in CH.

As can be seen from Table 2, according to the present invention, 0.6μ
A very fine SiC powder of less than m is obtained.

On the other hand, JP-A-59-1361 shown as a comparative example
Depending on the method shown in No. 6, reduction and carbonization were insufficient and only SiC powder containing amorphous Sing was obtained.

<Effects of the Invention> According to the present invention, SiO generated by reducing an SiQz-containing oxide with carbon or dimetallic silicon under reduced pressure
? By using ultrafine SiO powder obtained by condensing 8 gas in the gas phase as a raw material, fine and highly purified SiC fine powder can be industrially produced in large quantities.

[Brief explanation of the drawing]

FIG. 1 is a transmission electron micrograph showing the particle structure of SiO fine powder. Patent applicant Kawasaki Chotetsu Co., Ltd. No. 1 Figure 0.1 pm

Claims (1)

[Claims] (1) A mixture of SiO_2 powder or an oxide powder containing SiO_2 and a carbon-containing material and/or metal silicon powder, or a molded product thereof, is heat-treated under reduced pressure, and SiO fine powder is recovered from SiO vapor obtained. , a mixture of this SiO fine powder, a carbon-containing material, and SiC powder, or a molded product thereof, is heat-treated in Ar, H_2, CO gas, or a mixed gas thereof.
Method for producing fine powder.