JPS5891006A - Manufacture of alpha-type silicon nitride powder - Google Patents

Abstract

PURPOSE:To manufacture alpha-type Si3N4 powder in a high yield by hydrolyzing a liq. material prepared by adding carbon powder and Si3N4 powder or SiC powder to methyltrichlorosilane and by treating the resulting precipitate under heating in an N2 atmosphere. CONSTITUTION:To methyltrichlorosilane (A) having >=99% purity fed by an amount required to form 1 part by weight of SiO2 by hydrolysis and calcination are added 0.1-2 parts carbon powder (B) having <=1mum average particle size and >=99% purity and 0.005-1.0 part crystalline Si3N4 powder and/or SiC powder (C) having <=2mum average particle size and >=99% purity. The prepared liq. material is hydrolyzed, washed and dried. The resulting precipitate is heated to 1,300-1,500 deg.C in an atmosphere contg. N2 to cause reduction and nitriding reactions, or it is further treated under heating at 600-800 deg.C in an oxidizing atmosphere. Thus, high quality alpha-type Si3N4 powder having a uniform and minute particle size and suitable for use as a heat resistant high stress material is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a method for producing αS silicon nitride (α-type Si 3N4) powder.

(Prior art and its problems) For example, silicon nitride-yttrium oxide or magnesium oxide (S i 31'J4 Y2O3 or S
Since the i3N4-MgO-based sintered body has high mechanical strength, large size, and excellent heat resistance, attempts have been made to apply it to high-temperature gas turbine components. However, when the above-mentioned 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 impurity content, and it is desirable for silicon nitride to contain as much α-type SI3N4 powder as possible.

By the way, the general method for synthesizing SI3N4 powder is (1)
Method for nitriding metal silicon powder 3si+2N2→5I
3N4 (2) Gas phase reaction method using silicon tetrachloride, silane and ammonia as raw materials 35iC14+ 4 NH3→S i 3 N4 +1
2 Method of nitriding SiO obtained by reducing +31 IJ force (Sin2) such as HCl with carbon C of reaction stoichiometry 3 SiO2 + 6C + 2Nz → Si 3N4 +
6 CO is collected.

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 grains of Si are selected and pulverized after attenuation. 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 cannot be mass-produced as an inorganic heat-resistant material and is not suitable for industrial manufacturing.

Furthermore, in the case of (3), optically purified S + is used as a raw material.
Not only is it necessary to use 02 powder and C powder, but the product is a mixed system of α-type S' 3N4 + β-type S'3N4 + silicon oquine nitride (S i 2ON2 ) and SiC, etc. The disadvantage is that the rate is low. That is, in this case, although there is an advantage that no complicated reaction operation is required, as mentioned above, the yield (α
It is not practical because the content of Si3N4 is low.

Furthermore, when the above manufacturing methods (1) to (3) were used, it was difficult to reduce the particle size and to reduce the particle size and the variation in particle size. The inventors of the present invention have addressed these points and proceeded with their studies, and as a result, the above-mentioned silica (Si
n2) reduction, nitriding method (decomposition at high temperature)
Using methyltrichlorosilane as a raw material and hydrolyzing fine crystalline silicon nitride (Si3N4) powder together with C powder in a predetermined amount, if the reaction temperature is selected at a predetermined temperature, high quality It has been found that the α-type Si3N4 powder (remarkably fine particles) has a high yield and improves the refinement and uniformity of the particle size.

(Objective of the Invention) Based on this knowledge, the present invention has been developed to produce α-type Si3N4 powder suitable for Si3N4-based high-temperature, high-stress materials at a high yield and with fine particle size without requiring complicated operations or reaction equipment. The aim is to provide a manufacturing method that can improve uniformity and uniformity.

(Summary of the Invention) The present invention will be described in detail below.
02) 1. Carbon (c) powder 01 to 2 layers and granular silicon nitride (corresponding to that produced by hydrolysis and calcination treatment of k) are added to methyltrichlorosilane of
A liquid suspension obtained by mixing at least one of Si3N4) powder and silicon carbide (SiC) powder in a ratio of 0.005 to 1.0 ridges is hydrolyzed, washed, and dried.
, the resulting precipitate was heated in a nitrogen-containing atmosphere for 1300~
151) α-type silicon nitride (α-type 5i3N4) characterized by heat treatment at 0°C, nitriding reaction at the base of the lid, and if necessary further heating texture at 600 to 800°C in an oxidizing atmosphere. This is a method for producing powder. Methyltrichlorosilane-carbon-crystalline silicon nitride used as a starting material in the present invention
C-8! aN4) 5i02 (from CI-I3S'1C13) in terms of 81021 obtained by hydrolyzing and firing methyltrichlorosilane in a mixed system
-C-8i3N4 1:01~2:0.005~1.0
The reason for selecting the weight ratio is as follows. That is, conversion 5i0
If C is less than 0.1 heavy part per 21 heavy part, 5i02 remains unreacted and the production of polyacid 512ON2 is observed, but less α-view Si 3N4 is produced and 1 part of double This is because if the amount exceeds 100%, the formation of β-type SI3N4 is observed, resulting in a deterioration in the purity of α-313N4, and in particular, a decrease in the yield.

Crystalline S' 3 for parts by weight of monoconverted xSi021
The ratio of at least one of N4 rSiC is 0.005
If it is less than ti part, the effect of increasing the yield of α-type S i 3N4 is small, and on the other hand, if it exceeds 1 tli part, a powder with favorable powder characteristics obtained by oxide reduction cannot be obtained, and the added 5j
The characteristics of the 3N4 powder become so pronounced that the original purpose cannot be achieved. However, each raw material component of these CH3SI C13T C and crystalline S i 3N4 has a 99 coefficient I.
It is preferable to have a high purity of f or more, and as for the particle size, it is preferable that C has an average particle size of 1 μm or less, and that crystalline 5j3N4 has as fine particles as possible, for example, 2 μm or less. The crystalline Si3N4 used as a raw material is preferably in the α-type, but it may also contain the β-type or other elements such as /Ll,
Even if it is a solid solution, it is acceptable. Further, the same reaction promoting effect can be obtained by replacing crystalline 5i3N40 with crystalline silicon carbide, SiC, etc., alone or in a mixture thereof, or by replacing a portion of these with metal Si. However, crystalline SiC.

There is a tendency for the purity to be slightly inferior when using . The following uses of methyltrichlorosila/ and crystalline 5i3
The explanation will focus on N41 and 8 additions. Methyltolylchlorosilane ((y(3SiC13)U) Highly purified products are abundantly supplied as a by-product of the silicone industry.By the way, other silane compounds include tetrahydro7rane (SiH4) and silicon tetrachloride (SiC14). , tetraethquinane (Si(OC2Hs)4), methylsilane (CI(3S iHa ), tetramethoxysilane (S
i (Cot-I3)4), etc. However, among these, S l (OC2[(5) 4 ).

Raw materials such as Cl43Si and f3,5i (OCf(3)4) have the disadvantage that they cannot be completely decomposed due to difficult hydrolysis treatment conditions.If the reaction is heated in that state, the residual alkoxy groups will cause precipitation during heating. # Things aggregate, the reaction does not proceed smoothly, and the synthesized 5L3N4 powder becomes pure IW.
make it extremely bad. In this respect, methyltrichlorosilane is easy to hydrolyze, and as long as the heat generation is sufficiently controlled, a complete intermediate precipitate can be obtained according to the following reaction formula.

CH3S i C1l 3 + H20→CH3S i
03/2+ HCl If methyltrichlorosilane is used as the raw material here, a more favorable phenomenon occurs. In other words, a large amount of HCJ is simultaneously generated during hydrolysis, but
HCe has an excellent effect in removing impurities such as calcium (Ca) and iron (F"e) contained in C and crystalline 513N4. For example, silica (S 102 ) powder and mixing C2Si3N4 etc. in a ball mill to obtain S r 3 N4 powder.
When i3N4 powder is obtained, the impurity content is reduced to 1/10 or less compared to when 8+02 is used as the starting material. The addition of crystalline Si3N4 powder, which is another feature of the present invention, will be further explained.

In the present invention, cl-(3S i03/2-C crystalline S'3
When heating and firing the N4 mixture, the atmosphere is N2. N.I.
]3. Systems such as N2 hydrogen (1-(2), 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 highly pure α-type Si3N4. On the other hand, the firing temperature in this atmosphere containing N2 or NI3 as the main reaction gas is selected within the range of 1300 to 1500'O. The reason is that below 1300'O, S! 3
N4 is difficult to generate, and if the temperature exceeds 1500°0, SiC
This is because the desired α-type 5j3N4 powder suitable for high-temperature, high-stress materials cannot be obtained.

Furthermore, after heating and firing in an atmosphere using N2 as the main reaction gas, heat treatment in an oxidizing atmosphere is aimed at removing residual C, but the temperature is 600 - 600℃.
The range is selected to be 800°0.

As mentioned above (placement of 5i02, excess C in nitriding reaction)
According to the present invention, in which a predetermined amount of crystalline Si3N4 is used, the reduction of 5i02 is greatly promoted,
This powder has excellent properties such as small variations in diameter and particle shape, and the sintered body obtained using this powder has excellent high-temperature strength.

Here, the reason why the Si3N4 added in advance in the present invention is limited to crystalline materials will be explained.

Si3N4 can be obtained in different crystal forms, from amorphous to crystalline, depending on the manufacturing method and conditions. However, the Si3N4 added for ophthalmology in the present invention is Si3N4 produced in a gaseous state.
It acts as a nucleus for depositing and growing N4, and its crystalline shape, along with other characteristics such as purity and particle size, greatly influences the reaction rate, yield, and particle size and shape of the synthetic powder.

In other words, the nucleus itself must exist in a physically and chemically stable state during the Si3N4 synthesis process; for example, changes from amorphous to crystalline, grain growth, chemical composition changes, etc. This leads to a decline in nuclear function. 5L3N4, which is generally produced by vapor phase synthesis, mostly exhibits an amorphous crystalline form, although it depends on the synthesis conditions. This amorphous S
From a chemical perspective, i3N4 exhibits a content of Sl and N close to that of crystalline Si3N4, but from the point of view of its crystal structure, its arrangement is not necessarily regular, and it does not meet the conditions of other synthesis methods. #) It is something that can be seen.

However, this amorphous state is 1200-1600°0 l
Heat treatment with crystallinity changes it to crystallinity, but the reason is not clear, but it is always accompanied by coarsening of grain size and shape. When such amorphous 813N4 powder is used as the core shown in the present invention, the synthesis temperature head is almost the same as the temperature range where the non-crystalline state changes to the crystalline state, so the characteristics of the core change and the reaction is accelerated. , the effect of particle size and shape control is completely lost,
If the purity of the synthetic powder is low, try to coarsen the F1 particle size.

Furthermore, in the present invention, when methyltrichlorosilane is mixed with C crystalline S+3N4 and the like and hydrolyzed to form a precipitate, it is thought that the hydrolyzate is deposited around the carbon powder particles. However, the precipitate is 200-300'
It is preferable to heat-treat with O and dehydrate 1-, and in the Si3N4 powder synthesis reaction, the general formula (CE(
Since the compound represented by 3SiO3//2) is adsorbed on carbon, the contact area is large, and carbon reduction proceeds smoothly, and the alkyl group is easily substituted with nitrogen, so the nitriding reaction proceeds quickly.

However, in this case, the mixed fraction state of each raw material slightly affects the synthesis reaction, so it is necessary to It is preferable to improve.

(Example of the invention) Next, examples of the present invention will be described.

Shun's methyltrichlorosilane, which corresponds to hydrolysis and calcination treatment to produce 5lo2i heavy twill part, has a particle size of 0029 μm.
Crystalline Si3N4 with a particle size of 03 μm and 0.5 C overlapped part
A liquid mixture was prepared by adding 0.1 parts by weight. 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 and filtered, thoroughly removing H (J and f).
A drying process was performed for 3 hours at 110'O. This product was lightly pulverized using a ball mill, and
00'0.5 fi was left to react. Thereafter, to remove residual C, heat treatment was performed in air at 700°Q for 3 hours to obtain S'3''4 powder.
The total metal impurity 1 was 009% and the simultaneously generated 5iCti was 0.3%. In addition, the average particle size of the above synthetic powder was 1.2 μm, and α-8i3N
4 content was 95%.

In addition, as a result of examining the particle size distribution of the synthetic powder using a particle size distribution measuring device, it was found that Si3N4 particles with a particle size of 1.2 μm ± 10 cm accounted for 93 wt% of the total, and were composed of uniform particles. I understand. Other Examples 2 to 12
and 5i02. produced from the above methyltrichlorosilane as a comparative example. If C with a particle size of 0029 μm cannot be used (
Al and amorphous Si3N4 having a particle size of 03 μm were mixed in a predetermined ratio, and the properties of the α-8i3N4 powders obtained were evaluated in the same manner using a manufacturing method similar to Example 1 above. The manufacturing conditions and characteristics of the produced powders of Examples 2 to 12 and Comparative Examples are shown in the following table, including Example 1.

Blank space below (effects of the invention) As is clear from the above results, in the case of the example, α-8i3N4 accounts for 90 or more, and the N content (N ratio) is 34 to 34%. Since the value is as high as 38 cm, it can be seen that these α-8i 3N4 have high purity as nitrides, and furthermore, the particle structure of the synthetic powder has a very uniform particle size.

Agent: Patent Attorney Noriyuki Chika (1 other person) -35~

Claims (1)

[Claims] Silica (8i02) was added to methyltrichlorosilane (CH3S + C13) equivalent to 1 part by weight, 01 to 2 parts by weight of carbon powder, and crystalline silicon nitride (Si3N4).
A liquid substance prepared by adding at least one of silicon carbide (SiC) powder and silicon carbide (SiC) powder at a ratio of 5i020.005 to 1 part is hydrolyzed and washed, and the resulting precipitate is placed in a nitrogen-containing atmosphere. α characterized by heat treatment at 1,300 to 1,500'O to cause reduction and nitriding reactions.
Method for producing type silicon nitride powder.