JPS5932402B2 - 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 α-type silicon nitride (α-type S laN+) powder, and more particularly, to a method for producing α-type Si3N4 powder of high quality with a high yield.

For example, silicon nitride-yttrium oxide or magnesium oxide (s t 3N4 Y2O3 or Si3N
Since the 4-MgO-based sintered body has high mechanical strength and excellent heat resistance, attempts have been made to apply it 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 particularly important factors, are greatly influenced by the type of starting materials and the content of impurities, and it is desirable for silicon nitride to contain as much α-type 5t3N4 powder as possible.

By the way, the general method for synthesizing 5t3N4 powder is (1)
Method 3 for nitriding metal silicon powder S i+ 2N2→S t 3N4 (2) Gas phase reaction method 3 using silicon tetrachloride, silane and ammonia as raw materials S ice 4+4NH3-+S i3N4+12
HCl etc. (3) Method 3 of nitriding SiO obtained by reducing silica (SiO
+6CO has been taken.

However, in the case of 1), the nitriding of Si is an exothermic reaction, and in order to control the heat generation, a process must be devised. For example, relatively coarse particles of Si are selected and pulverized after nitriding.

For this reason, contamination with impurities is unavoidable (during the crushing process), and although there is no problem in using it as a general heat-resistant material such as refractory bricks, it is not suitable for high-temperature gas turbines.

In the case of (2), it is suitable for, for example, surface coating of semiconductor elements, but it cannot be said to be mass-produced as an inorganic heat-resistant material and is not suitable for industrial manufacturing.

Furthermore, in the case of (3), sufficiently refined SiO is used as the raw material.
Not only is it necessary to use 2 powder and C powder, but the product is a mixed system with α-type Si3N4, β-type 513N silicon oxynitride (S゛12ON2), and SiC, and the yield of α-type Si3N4 is low. It has the disadvantage of being low.

That is, in this case, although there is an advantage that no complicated reaction operation is required, as mentioned above, the yield (the content of α-type Si3N4 is low) is poor, so it is not practical.

The inventors of the present invention proceeded with studies to deal with these points, and as a result, as previously disclosed in JP-A-55-11360, in the reduction and nitriding method of silica (Si02) described above, it was decomposed at high temperature to become SiO2. If methyltrichlorosilane is used as a raw material and a predetermined amount of fine silicon nitride (SIA1%) powder is coexisted with C powder for hydrolysis, and the reaction temperature is selected to a predetermined temperature, high quality α-type 5i3N, powder (remarkably fine particles) was found to be obtained in high yield.

However, even in the above method, it was not always possible to achieve a yield sufficiently high for practical use.

In view of the above points, the present invention provides α-type 5t3N4 which is suitable for high-temperature and high-stress materials with a simplified manufacturing process and high yield.
The purpose is to provide a manufacturing method that can obtain powder.

The present invention uses methyltrichlorosilane (CH3SiC13
) with 0.1 to 0.3 parts by weight of carbon C powder and at least one of silicon nitride (S13N4) powder, silicon carbide (SiC) powder, and silicon oxynitride powder.
0.05 to 1 part by weight to obtain a liquid mixture;
a step of hydrolyzing the liquid mixture; a step of washing and drying after the hydrolysis to obtain a granular material; a step of pulverizing the granular material to obtain a fine powder of 50 μm or less; This is a method for producing α-type silicon nitride powder, which includes a step of heat treatment at 1300 to 1500° C. in an atmosphere to cause a reduction-nitridation reaction.

That is, the method of the present invention first uses methyltrichlorosilane-carbon-silicon nitride (CHAS tCA) as a starting material.
? 8102 obtained by hydrolyzing and firing methyltrichlorosilane in a mixed system of 3C513N4)
In terms of 1 part by weight, SiO□ (from CH3SiC13)-C-8t3N is 1:0.1 to 0.3:0.005
A liquid mixture is obtained by mixing at a ratio of 1.0 to 1.0 parts by weight.

The reason for limiting the ratio of each component in this step is as follows.

That is, the amount of carbon per part by weight of 5i021 reduces the yield, and while a large amount of 8i2ON2 is produced, the amount of α-type Si3N4 produced is small, and if it exceeds 0.3 parts by weight, a large amount of unreacted excess carbon occurs. As a result, the subsequent decarburization step becomes complicated, and the production yield of α-type Si3N4 decreases.

On the other hand, 5i3N4, Si for converted S 1021 parts by weight
The ratio of at least one of C and silicon oxynitride is 0.
If the amount is less than 0.005 parts by weight, the effect of increasing the yield of α-type Si3N4 will be small. On the other hand, if it exceeds 1 part by weight, it will not be possible to obtain a powder with favorable powder properties obtained by oxide reduction, and the added 813N4 powder will not be as effective. The characteristics become noticeable and the original purpose cannot be achieved.

However, these CH35tC7a, C and Si3
It is preferable that each raw material composition of N4 has a high purity of about 99% or more, and regarding the particle size, C has an average particle size of 1.
Si3N4 is preferably as fine as possible, for example, 2 μm or less.

The 5i3N used as a raw material is preferably in the α form, but it may also be in the β form or in solid solution with other elements such as A7,0.

Furthermore, the same reaction promoting effect can be obtained by replacing Si3N4 with SiC, a silicon oxynitride compound such as 512ON2 alone or a mixture thereof (including S t3N4 ), or by replacing a part of these with metal Si.

However, when S i C or S i2 CH2 is used, there is a tendency for the purity to be slightly inferior.

Note that methyltolylchlorosilane (CHs SiCi!
a) High purity products are abundantly supplied as by-products of the silicone industry.

By the way, other examples of this kind of silane compound include, for example, tetrahydrosilane (S t H+'), silicon tetrachloride (S
1ce4), tetraethoxysilane (Si(OC2H
6)4), methylsilane (CHas iHa), tetramethoxysilane (Si(COHa)+), etc.

However, Tekore et al.
H3S iHs.

Raw materials such as S i (0CHa ) 4 have the disadvantage that hydrolysis treatment conditions are difficult and they cannot be completely decomposed.

If the reaction is carried out by heating in this state, the precipitate will coagulate during the temperature rise due to the residual alkoxy groups, the reaction will not proceed smoothly, and the purity of the synthesized S s 3N 4 powder will be extremely deteriorated.

In this respect, since methyltrichlorosilane is extremely reactive, methylsilicic acid (CH3SiO3//2) is produced at a substantially 100% production rate according to the following reaction formula.

CHa S t CIj a+H20→CH3S 10
When 3/U+HCA and methyltrichlorosilane are used as raw materials, an ingenious phenomenon occurs.

In other words, a large amount of HC'A is simultaneously generated during hydrolysis, but HCl is a mixture of calcium (C and calcium contained in 5i3N4, etc.).
It has an excellent effect in removing impurities such as Ca) and iron (Fe).

For example, silica (SiO□
) powder and mixing C2Si3N4 etc. in a ball mill to obtain 5iaN4, when obtaining 512N4 powder from methyltrichlorosilane according to the present invention, the amount of impurities is lower when using SiO□ as a starting material and then in the method of the present invention. , washing the methyl l-IJ chlorS t3N4 mixture,
The granular material obtained by drying is pulverized to form a fine powder.

That is, by pulverizing the granular material to 50 μm or less using a powder grinding device such as a ball mill, the degree of mixing can be significantly improved.

As a result, the decarburization step near the final step can be extremely simplified, and α-type Si3N powder suitable for high-temperature and high-stress materials can be obtained at a high yield.

The above effects of the present application can be obtained because the redox ability of the pulverization process group is remarkable, and C in the CH3 group is α-type Si.
This is thought to be because it is used as part of the reducing carbon necessary for the synthesis of 3N4.

In other words, in the present invention, for methyltrichlorosilane, which is suitable for producing 1 part by weight of silica (SiO□),
It is believed that the entire theoretical amount of carbon contained in methyltrichlorosilane contributes to the reduction reaction, and by adding a minimum of 0.1 parts by weight of carbon, it becomes possible to obtain a good α-type Si3N4.

The maximum amount of Naori-Bonn varies somewhat depending on the degree of pulverization, but in the case of pulverization to 50 μm or less as in the present application, it is sufficient to use 0.3 parts by weight.

As a result, surplus carbon in the manufacturing process is drastically reduced, and the decarburization process is extremely simplified. Furthermore, it becomes possible to obtain α-type S 13N4 at a high yield.

Further, in the present invention, when heating and baking the mixture of methyltrichlorosilane, the atmosphere is N2. NI (3°N2-
Systems such as hydrogen (N2) and N2-inert gas may be mentioned, but the main reaction gas must be N2 or NH3.

The reason for this is that it has been experimentally confirmed that it greatly influences the final production of high purity α-type 5t3N4.

On the other hand, the firing temperature in the atmosphere containing N2 or NH3 as the main reaction gas is selected within the range of 1300 to 1500°C.

The reason for this is that Si3N4 is difficult to form at temperatures below 1300°C, and SiC is difficult to form at temperatures above 15000°C.
This is because 3N4 powder cannot be obtained.

Furthermore, after heating and firing in an atmosphere using the above-mentioned N2 as the main reaction gas, if necessary, under a simple oxidizing atmosphere,
The remaining C is removed by heat treatment at 800°C.

As described above, in the reduction and nitriding reaction of 5IO2, C in the CH3 group is used, and in particular, according to the present invention, in which a predetermined amount of St3N4 is coexisting, the reduction of 5102 is greatly promoted, and there is an advantage that there is little variation in diameter and particle shape. This powder has excellent properties, and the sintered body obtained using this powder has excellent high-temperature strength.

Furthermore, in the present invention, methyl l-IJ chlorosilane is
, S t3N4, etc. and hydrolyzed to form a precipitate, it is thought that the hydrolyzate is deposited around the carbon powder particles.

However, it is preferable to heat-treat the precipitate at 200 to 300°C to dehydrate it, and in the 5t3N4 powder synthesis reaction, since it is adsorbed on carbon, the contact area is large, and carbon reduction proceeds smoothly. Since the alkyl group is easily substituted with nitrogen, the nitriding reaction proceeds quickly.

Next, examples of the present invention will be described.

Methyltrichlorosilane that produces 1 part by weight of methylsilicic acid in terms of 5i02, C with a particle size of 0.029 μm is
．． A liquid mixture was prepared by adding 2 parts by weight and 40.1 parts by weight of S t 3N having a particle size of 0.3 μm.

A large amount of pure water was added to this liquid mixture, and the mixture was hydrolyzed while controlling heat generation to form a precipitate.

This precipitate was washed with water to sufficiently remove HCA, and then dried at 110°C for 3 hours. The resulting granular material was ground in a ball mill for 5 hours to form a fine powder with an average particle size of 20 μm. Grind to 1400°C5 in a nitrogen stream
The mixture was left for hr to react.

After that, in order to remove residual C, the
After heat treatment, Si3N4 powder was obtained.

The powder thus obtained had a purity of 99% or more, the total amount of metal impurities was 0.06% or less, and the amount of SiC simultaneously produced was 0.3%.

The average particle size of the above synthetic powder is 12 μm, α-8t3
The N4 content was 95%, and the yield reached about 60%.

As other Examples 2 to 12 and a comparative example, Si3N4 with the above methyltrichlorosilane particle size of 0.029 μm (7) 01 particle size of 0.3 μm was mixed at a predetermined ratio, and the manufacturing method according to Example 1 was carried out. , respectively obtained α-8l 3
The characteristics of N4 powder were similarly evaluated.

The manufacturing conditions, characteristics of the produced powders, and yields of Examples 2 to 12 and Comparative Examples are shown in the following table, including Example 1.

As is clear from the table, in the case of the examples, α-8t3N4 accounts for 90% or more of the obtained powder, and the N content (N rate) is as high as 34 to 38.6%.
8i3N4 also has high purity as a nitride.

As is clear from the above results, by using the method of the present invention, α-type 5t3N4 powder, which is excellent as a high-temperature and high-stress material, can be obtained through a simplified manufacturing process, and in particular, granular material can be converted into fine powder of 50 μm or less. It was confirmed that the effect of the present application can be sufficiently achieved by pulverizing the powder to 100%.

Claims (1)

[Claims] 1 Methyltrichlorosilane (CHs S) which produces 1 part by weight of methylsilicic acid in terms of silica (Sin2)
t C12), 0.1 to 0.3 parts by weight of carbon powder, silicon nitride (s 13N4 ) powder, and silicon carbide (
at least one of SiC) powder and silicon oxynitride powder
A step of adding seeds in a proportion of 0.005 to 1 part by weight to obtain a liquid mixture, a step of hydrolyzing the liquid mixture, and a step of washing and drying after the υ Hinei decomposition to obtain a granular material. A step of finely pulverizing the granular material to obtain a fine powder of 50 μm or less;
There is also a method for producing α-type silicon nitride powder, which is characterized by comprising a step of heat treatment at 500°C and a reduction-nitridation reaction.