JPS606884B2 - Method for producing α-type silicon nitride powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing Q-type poppy nitride, bare (Q-type Si3N4) powder, and relates to a method for producing Q-type Si3N4 powder of high quality with a high yield.

For example, silicon nitride, yttrium monoxide or magnesium oxide (Si3N4-Y203 or Si3N4-
Since Mg○)-based fried stripes have high mechanical strength and excellent heat resistance, attempts have been made to apply them to high-temperature gas turbine components.

However, when the Si3N4-based sintered body is used as a high-temperature, high-stress material, physical and chemical stability and reliability at high temperatures are strictly required. Thermal and mechanical properties, which are especially important factors, are greatly influenced by the type of starting materials and the content of impurities, and it is desirable that the material contains as much Q-type Si3N4 powder as possible. By the way, the synthesis method for Si3N finalization is generally '1
} Method of nitriding metal poppy and raw powder $i+2N2→
Si3N4■ Gas-phase reaction method using poppy tetrachloride, base, silane, and ammonia as raw materials $iC 4 14NH3→Si3
A method of nitriding Si○ obtained by reducing silica (Si02) with carbon (C) in a reaction stoichiometric ratio is being explored.

All of these methods have a long lifespan, and it is dangerous to judge which method is simply superior, so the method that meets the required characteristics is usually adopted.

Among these, for the Si02 reduction method [3'], silicon oxynitride (Sj20N2), charcoal, and elemental (SI
A disadvantage is that the purity of the Si3N4 powder produced by preserving C) is reduced. To improve this, by adding a small amount of metal powder (Si) to the reaction system, a fairly high quality Si powder can be synthesized. However, the effect of adding the Si powder greatly depends on the average particle size of the added Si powder, which is generally a raw material. It is necessary to add 0.1 or more in weight ratio to Si02, and as a result, the resulting powder is observed to have a coarse grain pattern. The inventors have developed this Si02
In Sj3N4 synthesis by reduction, the particle size of Si powder and S
As a result of conducting experiments and studies focusing on the relationship between the effects of i addition, we found that when using particularly fine Si powder, even small amounts of Si powder are effective, and that the purity and properties of synthetic powders can be further improved. did.

In other words, a mixed powder made of amorphous high-purity Sj02C of 0.1 ym or less and limited to 0.5 Yamakaze or less of added Si powder is subjected to a nitriding reaction at a predetermined temperature, and if necessary, heat-treated in an oxidizing atmosphere. Based on this knowledge, the present invention is based on the knowledge that the Q-type Si3N4 content is extremely high and a fine powder is synthesized. The present invention aims to provide a manufacturing method capable of obtaining Q-type Si3N4 powder suitable for use in high-temperature, high-stress materials with a high bridge yield.

The present invention will be described in detail below.The present invention consists of 1 silica (Si02) powder, which is amorphous and has an average particle size of 0.1 degrees or less, and carbon (1), which is amorphous and has an average particle size of 0.1 degrees or less, by weight.
C) A mixed powder consisting of a powder of 0.4 to 4, and a metal poppy with an average particle size of 0.5 or less, and an elemental (Si) powder of 0.01 to 0.1, was heated to 1350 to 150 in an atmosphere containing nitrogen.
Q-type silicon nitride (Q-Sj3N4) characterized by being heat treated at 000C, reduced and nitrided, and if necessary further heat treated at 600 to 80000C in an oxidizing atmosphere.
This is a method for producing powder.

In the silica carbon-silicon (Si02-C-Si) mixed system used as a starting material in the present invention, amorphous Si02:amorphous C:Sj is 1:0.4 to 4:0.01.
The reason why the weight ratio is selected to be 0.1 is as follows. That is, if the weight ratio of C per Si021 is less than 0.4, Si02
remains as a hydrogen reaction, and a large amount of Si202 is produced, but on the other hand, the amount of Q-type Si3N4 produced is small, and when it exceeds 4, the production of B-type Si3N4 and SIC becomes significant, and as a result, the purity of q-Si3N4, Yield decreases.
On the other hand, the weight ratio of Si to Si021 is 0.01~
When the amount is 0.1 parts by weight, the effect of increasing the yield of Q-Si3N4 is large and high quality products with uniform particle size can be easily obtained.
Therefore, it is preferable that each of these amorphous Si02, C and Si raw material compositions have a high purity of about 99% or more, but what is more important is the average particle size of the raw materials,
For 02 and C, an amorphous, ultrafine powder of 0.1r or less is selected, and the average particle size of the added Si must be 0.6 grains or less.

If the average particle size (particle size) is larger than the above, in any case, there will be a little more SIC, and undesirable results are likely to occur, such as the formation of SIC, a decrease in the reaction rate, and an increase in the particle size of the produced powder. Commercially available amorphous Si02 and C powders such as Si02 and C powders can be used, and Si metal powders obtained by thermal decomposition of gas phase reaction of Si ratio, which is a common method for producing Si metal powders, can be used. It can be used in the form of granules.In the present invention, when heating the Si02-C-Si mixture, the atmosphere is N2, NH3, N2 monohydrogen (
2) A system such as 9N2-inert gas may be used, but the main reaction gas must be N2 or N gas.

The reason is that these gases eventually turn into high-purity Q-type Si3.
This is because it has been experimentally confirmed that it greatly influences the generation of N4. On the other hand, the heating and firing temperature in an atmosphere containing N2 or NH3 as the main reaction gas is 1350 to 1500q.
selected within the range o. The reason for this is that if it is less than 135,000, it is difficult to generate Si3N4, and if it exceeds 150,000, SIC will be generated, making it impossible to obtain the desired Q-type Si3N4 powder suitable for high-temperature, high-stress materials. Furthermore, after heating in an atmosphere using N2 as the main reaction gas, heat treatment in an oxidizing atmosphere is performed as necessary to remove residual C, but the temperature is 600℃. ~80,000.

That is, if heat treatment is performed at a temperature outside the above-mentioned temperature range when removing unreacted C, the Q-type Si3N4 produced will be oxidized, making it difficult to obtain the required Q-type Sj3N4 powder. As described above, in the reduction and nitriding reaction of Si02, an excess of C far exceeding the reaction stoichiometric ratio is used, and in particular, according to the present invention, a predetermined amount of fine Si is coexisting.
The reduction of 2 is greatly promoted, and the nitridation of Si also progresses smoothly, resulting in high-quality stretchable Si3 with a high content of Q-type Sj3N4.
N4-based powder can be obtained in good yield.

However, according to the present invention, Si, which is required to have high temperature and high stress properties,
The reason why a Q-type Si3N4 powder suitable for producing a 3N4 composite is easily obtained is considered to be as follows. That is, as a primary reaction, Si020C→Si020CO proceeds. This reaction is a solid phase reaction, and the higher the C/Si02 ratio is, the more smoothly it proceeds, and the generated Si0 easily reacts with N2 or N melon in the gas phase. However, in this case, if the amount of C is around the reaction stoichiometric ratio or slightly excessive, the generation of Si0 is insufficient, so the generation of Si20N2 is observed, and Sj20N2
However, as mentioned above, since the amount of C is in large excess compared to the reaction stoichiometric ratio, it becomes extremely difficult to convert Si3N4 to Q-type Si3N4.
It is thought that the generation of 20N2 is suppressed and Q-type Si3N4 is easily generated. In this way, the presence of an excessive amount of C facilitates the formation of Q-type Si3N4, but on the other hand, it
and other impurities, resulting in a relative decrease in the content of Q-type Si3N4. However, in the present invention, a predetermined amount of Si powder is also allowed to coexist in the reaction system. Since the Si powder present here is fine, it easily nitrides itself, providing fine nuclei for the generation of Si3N4 via Sio from the original reaction with Si02 and C, and at the same time reacting with Si02 to generate Si○. It produces two promoting effects. However, the effect of the Si powder that coexists here is greatly influenced by its particle size, and when coarse-grained Si is used, the reaction rate is slow, so the effect of promoting Si○ formation is small, and Si3N4 due to nitridation of Si itself is also affected by the particle size. Since Si3N4 is coarse and a certain amount is required to finally produce the desired Si addition effect, the produced Si3N4 has a large particle size. In this regard, in the present invention, the particle size of added Si is reduced to 0.5A.
Because it is limited to less than the skin, the speed at which it reacts with Si02 to generate Sj○ is fast, and Si3N4 itself has become a mountain.
Since the grains of Si3N4 are also fine, the Si3N4 produced with these fine and fine Si3N4 as a nucleus is also fine, and the effect is fully exerted even with the addition of grains.As a result, even though the reaction time is short, the grain size is uniform and the quality is high. powder is synthesized in high yield. Thus, according to the present invention, a high-quality Q-type Si3N4 powder with a high content rate of Q-type Sj3N4 and a significantly low content of impurities such as SIC can be obtained, so the method of the present invention requires high temperature and high stress. It can be said that it is suitable for producing Si3N4-based powder, which is a raw material for Si3N4-based sintered structural materials.

Next, examples of the present invention will be described.

Examples Average particle size: 0.013 Buddha's amorphous Sj02 powder, average particle size: 0.029 Buddha's amorphous C powder, and average particle size: 0.2
The Si powder of France was mixed at a predetermined weight ratio, reacted in N2 gas at 1400°C, and then heat-treated in air at 700°C to produce Si3N4 powder.

For each Si3N4 powder thus obtained, the average particle size, N content rate (wt%), Q-type Si3N4 content (wt%)...confirmed by X-ray diffraction pattern..., SIC content (wt%) ) are shown in Table 1. Table-1

Claims (1)

[Claims] 1 Amorphous silica (SiO_
2) 1 part by weight of powder, 0.4 to 4 parts by weight of amorphous carbon (C) powder with an average particle size of 0.1 μm or less, average particle size of 0.5 μm
A mixed powder consisting of 0.01 to 0.1 parts by weight of metallic silicon (Si) powder of 1,350 to
A method for producing α-type silicon nitride powder, which comprises heating at 1500°C to cause reduction and nitriding reactions.