JPS59223214A - Manufacture of hyperfine-grained sic powder - Google Patents

Abstract

PURPOSE:To manufacture easily hyperfine-grained SiC powder at a low cost by adding boron or a boron compound to a mixture of SiO2 powder with carbon powder by a specified amount basing on the amount of SiO2 and by carrying out reduction and carbonization at a high temp. CONSTITUTION:Boron or a boron compound is added to a mixture of SiO2 powder of <=10mum particle size with carbon powder of <=1mum particle size in 0.004-0.4 atomic ratio of B/Si. The resulting mixture is subjected to reduction and carbonization at 1,500-2,000 deg.C. Hyperfine beta-SiC powder of <=about 0.1mum particle size is manufactured by a solid phase reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing silicon carbide powder, and particularly to a method for producing ultrafine silicon carbide powder.

In recent years, from the standpoint of energy and resource conservation.

Ceramics are attracting attention as high-temperature structural materials.

Among them, silicon carbide is expected to be the most promising material along with silicon nitride. Furthermore, silicon carbide plays an important role as a special electronic material.

Conventionally, silicon carbide has been mainly produced by the following three methods.

(Reduction carbonization reaction of silica with carbon ~ 2500°C St O, +30- SiO+ 2 C0 (2) Gas phase reaction between silicon halide and hydrocarbon > 1500°C SiX4+OH4SiO+ 4HX (x: halogen atom) (3) Organosilicon Thermal decomposition reaction of compound +31(OH,)4-≧ko≦tri'KL-SIC!+
30H4 Among these methods, the method has been known for a long time as the Aches button method for producing A-type silicon carbide, but it has the disadvantage of being produced at a high temperature of 2000°C or more and having a high energy consumption rate. In addition, it is difficult to obtain high-purity fine particles, so long hours of grinding and purification are required for raw material powder for engineering ceramics and electroceramics), resulting in a very expensive product. I don't get it. Although it is possible to obtain fine particles with a particle size of submicron or less using methods (2) and (3), the raw materials are difficult to obtain and the yield is low, making it difficult to be an economical process.

Furthermore, many proposals have been made regarding the production method of β-8iO powder by the reduction carbonization method of silica, but in all of them the resulting SiO powder has a particle size of 1 μm or more, which is not preferable as a raw material for sintering.

An atomization step is required, and like the ACheIllOrI method, a large amount of energy is required for pulverization, and impurity contamination from the pulverizer may also be a problem.

In this way, the reduction carbonization method of silica, which is a convenient manufacturing method in terms of raw materials, has many applications including raw material powder for sintering, ultra-precision abrasives, and dispersion plating for sliding parts. It was not possible to obtain ultrafine particle SiO, which is commonly required for various uses.

In view of these problems, the present inventors have conducted intensive studies on a method for obtaining ultrafine SiO powder using a silica reduction carbonization method, and have found that boron or a boron compound is added to a raw material mixture consisting of silica and carbon. We have discovered that this objective can be achieved by
, 21r/11), and the BET surface area is 17rr?, which can be used satisfactorily for various purposes. The present invention was achieved by discovering that SiO having a diameter of /f or more (BET equivalent diameter of 0.1 μm or less) can be easily obtained.

The gist of the present invention is to provide silica powder with a particle size of lOμ or less and a particle size of lμ or less.
Add boron or a boron compound to the following carbon powder mixture to silica (B/Si (atomic ratio) = 0.004~
Add so that it is in the range of 0.4, 1500-2000
This is a method for producing ultrafine SiO powder, which is characterized by carrying out a reduction carbonization reaction at a temperature of .degree.

The silica powder used in the present invention is crystalline.

It does not matter whether the particles are amorphous or not, but it is preferable that the particle size is 10 μm or less. Further, the particle size of the carbon powder is preferably lμ or less.

From this point of view, carbon black is suitable.

When the particle size of both silica powder and carbon powder exceeds the above range, the BET surface area of the resulting SIC becomes small. In addition, in the present invention, the silica source needs to be silica powder and the carbon source needs to be carbon powder, and in order to uniformly disperse Si and C, at least one of the two raw materials is used in a liquid state. Although a method is proposed, if such a method is used.

There is no effect of atomization of the produced 810 particles due to the addition of boron.

In addition, B and A1, which are known as anti-O sintering aids, are added to SiO powder during the production of SiO powder.
In order to uniformly mix it into O, a method has been proposed in which it is added to silicon raw materials and carbon raw materials in advance during the production of sia powder (4I Publication No. 57-59208).

The presence of aluminum tends to promote grain growth and has no effect on grain atomization.

The boron source used in the present invention includes:

In addition to boron, boron compounds are used, and in A-isomer,
B4O5B! 01s HsBO, 5iB4, etc.

The amount of boron (compound) added is B/
The atomic ratio of B i is in the range of 0.004 to 0.4,
More preferably, the range is from o, ooa to 061.

If the atomic ratio of boron is less than 0.004, there will be almost no effect of making the particles fine, and if the atomic ratio exceeds 0.4, there will be negative effects such as a decrease in high temperature strength when made into a sintered body. The materials are also expensive, which is not desirable.

If the raw material system containing silicon, carbon, and boron prepared as described above is fired in a conventional manner using a solid-phase reaction method, a BIT surface area of 17 m'/ or more (BET equivalent diameter of 0.5 m') can be obtained.
1μ or less), and the average particle diameter by SEM photograph observation is 0.
It is possible to obtain a silicon carbide powder mainly composed of β type having a particle diameter of Jμ or less. Until now, it was known that β-81a powder with a particle size of 0.1 μ or less could only be produced by a gas phase method using plasma or laser, etc.; β-8iO powder can be easily and inexpensively produced.

This will be explained in more detail below using Examples and Comparative Examples.

Examples 1-8 Silica, carbon and boron (compounds) as shown in Table 1
were blended so that c/5io2 (mole ratio) = 3.0, and then mixed in a plastic ball mill for 10 hours. This mixture was fired in a Tammann furnace at 1650° C. for 1.5 hours under an Ar gas atmosphere to obtain ultrafine β-5ic powder as shown in Table 1.

It was confirmed that the BIT equivalent diameter was almost the same as the average particle diameter based on 611M photographic observation. In the following comparative example, SiO powder was produced under the same conditions except for the raw materials.

Comparative Examples 1 to 3 Table 1 shows the results when boron was not added and when the particle sizes of silica and carbon were changed.

Comparison of several kinds: 100 m of water with 100 m of sucrose and 1 f of H, BO
.

A solution of the above was added to 100f of tetraethyl silicate and hydrolyzed to obtain a uniform gel.

After preliminary drying, this product was placed in a Tamman furnace, and the temperature was gradually raised, and the same firing as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 5 The amount of boron added was small, B/s1 = o, oo l.

Firing was carried out in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 6 The compositions of silica, carbon, boron, and aluminum shown in Table 1 were used, and the same firing as in Example 1 was performed. The results are shown in Table 1.

Procedural amendments, August 1982, Director General of the Patent Office, Manabu Shiga, Indication of the case, 1982 Patent M No. 933652, Name of the invention, Process for manufacturing ultrafine 810 powder, 3, Person making the amendment, 4, Agent Address: 3-7 Kanda Nishiki-cho, Chiyoda-ku, Tokyo (Kowa-Hashi Building) 5. Date of amendment order: Voluntary amendment 7. Column 8 of "Detailed description of the invention" in the specification subject to amendment: Existence of amendment (Replace J5iB4J on page 5, line 15 of the specification with [s
IB, correct J.

(2) On page 6, line 15, "09. is." .

In general, it is considered ideal that raw material powder for sintering should consist of only pure phases, but β-S
In the production of 'Ia @ powder, 2
contains Hα, but by boron addition according to the present invention, 2
It also has the feature of being able to significantly reduce the proportion of Hα.

Therefore, with the same content of 2)1α, production can be performed at a lower temperature than in the conventional method. ” is inserted.

(3) 121 (α=I9XJ, “2
Insert ``Hα=26%'' and ``2Hα=25 blades'' below the margin of Table 1. [(Note) 2Hα is calculated from the formula of Suzuki et al. Ta. ” is inserted.

Claims (1)

[Claims] (Li) Boron or a boron compound is added to a mixture of silica powder with a particle size of 10 μ or less and carbon powder with a particle size of 1 μ or less so that B/Si (atomic ratio) to silica is in the range of 0.004 to 0.4. A method for producing ultrafine SiO powder, characterized in that a reduction carbonization reaction is carried out at a temperature of 1500 to 2000°C.