JPS5950007A - Precursor for sintered silicon nitride body and manufacture of sintered silicon nitride body using it - Google Patents

Abstract

PURPOSE:To obtain easily a sintered silicon nitride body of high quality by reacting a silicon compound with a hydrogen compound of nitrogen in a plasma atmosphere, press-molding the resulting fine-grained powder, and sintering it. CONSTITUTION:Silicon hydride, silicon halide or a mixture thereof is reacted with a hydrogen compound of nitrogen in a plasma atmosphere to form fine- grained powder as a precursor for a sintered silicon nitride body. Each particle of the powder contains hydrogen, and nitrogen and silicon are contained as a whole in a nonstoichiometric ratio represented by Si3N(4-x) (x>0). The precursor is press-molded and sintered in a nitrogen atmosphere. Hyperfine-grained silicon nitride powder having about 100-5,000Angstrom grain size is formed by reacting the silicon compound with the hydrogen compound of nitrogen in the plasma atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silicon nitride sintered body. More specifically, the present invention relates to a precursor material for a silicon nitride sintered body suitable for manufacturing a silicon nitride sintered body, and a method for manufacturing a silicon nitride sintered body using the same.

Silicon nitride sintered bodies have excellent high-temperature strength, thermal shock resistance, and oxidation resistance, so they can be used as high-temperature structural materials for gas turbines, diesel engines, etc., or as cutting tools, contributing greatly to energy and resource savings. It is important as one of the high-performance materials that can perform

Conventionally, silicon nitride sintered bodies have been manufactured by a reaction sintering method or a high temperature sintering method.

As a reaction sintering method, for example, a mixture of silicon or silica powder and carbon powder is heated to about 1300 to 17
A method of heating at 00°C and nitriding (for example, Japanese Patent Application Laid-open No. 47
-7211, 52-5700, 53-1023
Alternatively, a method has been proposed in which a hydrogen compound of silane gas and nitrogen is reacted in a gas phase in a temperature range of 800 to 1900° C. (for example, Japanese Patent Application Laid-open No. 130300/1982).

However, when using silica powder, for example, it is not easy to make fine silica particles, and it is extremely difficult to completely nitride the inside of the particles, so silicon may not be present in the sintered body. Therefore, the strength of the resulting silicon nitride sintered body is not very high, and both methods also have drawbacks such as requiring an extremely long heating time. .

On the other hand, in the high-temperature sintering method in which fine silicon nitride powder is synthesized and sintered, silicon nitride is a substance with strong covalent bonds, so the sinterability is very poor, and hot pressing at high temperatures is difficult. Due to the dissociation of Si3N4 it is difficult and it is necessary to add a suitable binder.

In addition, in order to obtain a sintered body with a complicated shape, a method of sintering under normal pressure is advantageous, and for this purpose, Al2O2, MgO
, M Periodicity Table 1 [Sintering aids such as oxides of group Ia elements must be added and fired.

However, since these additives form a low melting point grain boundary phase, there is a drawback that the high temperature strength of the sintered body is significantly reduced.

As a technique to improve these drawbacks, there is a method of producing fine powder of silicon nitride by blowing a silicon compound into a nitrogen plasma flow (for example, Japanese Patent Application Laid-Open No. 116604/1982).
has been proposed, but even this technique does not improve the difficulty of high-temperature sintering.

As a result of intensive research in order to solve this conventional drawback, the present inventors discovered that Si3N (4-
The existence of a substance having a composition ratio represented by
The inventors have also discovered that a high-quality silicon nitride sintered body can be easily converted from this substance, and have arrived at the present invention.

Therefore, a first object of the present invention is to provide a silicon nitride precursor that can easily produce a high-quality silicon nitride sintered body.

A second object of the present invention is to provide a method for easily producing a sintered body of silicon nitride from the silicon nitride precursor.

That is, the present invention provides a fine powder produced by reacting a silicon compound selected from silicon hydride or silicon halide, or a mixture thereof, with a hydrogen compound of nitrogen in a plasma atmosphere, the fine powder Each particle contains hydrogen, and the overall composition ratio of nitrogen and silicon is Si3N (4-X)
, a precursor for a silicon nitride sintered body characterized by a non-stoichiometric ratio represented by (X>O), and a silicon nitride sintered body using the precursor. This is a method of manufacturing.

The silicon hydride used in the present invention can be arbitrarily selected from compounds represented by the general formula 5inH2n+2, such as silane and disilane.

The silicon halide used in the present invention broadly includes halides of the silicon hydride described above, but in particular SiH (
4-n) A halogenated silane represented by Xn (X represents halogen) is preferred.

In the present invention, the raw material gas for silicon can be arbitrarily selected from the above silicon hydride or silicon halide, and these may be used alone or in combination of two or more.

As the nitrogen hydrogen compound used in the present invention, either ammonia or hydrazine may be used. Furthermore, even if a gas containing a mixture of nitrogen and hydrogen is used, substantially the same results as in the case of using a hydrogen compound of nitrogen can be obtained.

Furthermore, when the raw material gas for silicon itself contains hydrogen atoms, for example, SiH4, a mixed gas of the raw material gas containing hydrogen atoms and nitrogen is placed under plasma and other raw material gases containing hydrogen gas are mixed. It doesn't have to be used.

In the present invention, the ratio of the hydrogen compound of nitrogen and the raw material gas containing silicon (for example, St H4/NH3 (molar ratio)) is 10
-1/20 preferably 1-1/3, and the total reaction pressure is 0.05-100 torr, preferably 1-5 torr
It is r.

The plasma state in the present invention can be caused to appear by various discharge methods such as high frequency discharge and arc discharge, or by a plasma jet method.

The preferred discharge power is 1 when the cathode area is 50c+ (
~1000 watts 150 cd, more preferably 10-3
00 watts 150-.

According to the present invention, when a silicon compound and a hydrogen compound of nitrogen are reacted in a plasma atmosphere, the particle size is about 100 to 5000.
A ultrafine silicon nitride powder is produced. In this case, by adjusting reaction conditions such as raw material gas composition, reaction pressure, and input plasma discharge power, hydrogen can be contained in the silicon nitride powder, and the composition ratio of nitrogen and silicon can also be adjusted.
Non-stoichiometric (Si3N (4-x), x>O
) can be done. This means that, depending on the reaction conditions, the resulting fine particles lack nitrogen and contain 5t-H and 5t-3i bonds.

In this way, silicon nitride powder that contains hydrogen and is somewhat deficient in nitrogen can easily be formed into a completely nitrided silicon nitride sintered body by press-molding it and firing it at high temperature in a substantially nitrogen atmosphere. Since it can be obtained, it can be said to be a precursor of silicon nitride sintered bodies.

This is because when the precursor is pressure-molded and calcined at high temperature under a nitrogen atmosphere, bound or unbound hydrogen in the precursor is released, or unreacted hydrogen is released due to cleavage of the 5i-St bond. At the same time that bonds are formed, nitridation progresses as the formed dangling bonds combine with nitrogen in the atmosphere, and at the same time, rearrangement and rearrangement of atoms in the crystal occur, resulting in cross-linking between particles. It is thought that this progresses, resulting in complete nitriding and sintering.

These results show that before and after heating the precursor to 350 to 900°C, a weight loss after heating was observed as a result of measurement using a thermobalance (Differential Thermal Microbalance PGD-5000, Vacuum Science and Technology Department). This was also confirmed because an increase in weight was observed after heating at 1200° C. or higher in a nitrogen atmosphere.

The precursor can therefore be represented by the general formula Si3NχHy, which was also confirmed by infrared spectroscopy.

This is a new substance that has not been described in any literature.

In the firing reaction for producing a silicon nitride sintered body from the precursor, it is preferable to use a pressurized nitrogen atmosphere, and if necessary, halogen gas, oxygen, -nitrogen oxide or One or more mixed gases selected from nitrogen dioxide may be added.

Since the powder produced according to the present invention is produced by a gas phase reaction in a plasma atmosphere, the particle size of the particles is 100.
In addition to being ultrafine particles of ~5000A, they are almost spherical in shape and have uniform particle size distribution and composition distribution, which are characteristics of general reactions in a plasma atmosphere. It has the characteristic that the energy density of can be suppressed to a low level, and therefore it is possible to avoid contamination of adsorbed impurities in the reaction chamber. All of these characteristics are advantageous and match the properties required of the silicon nitride precursor powder in order to obtain a silicon nitride sintered body that is easy to sinter and has excellent properties.

Furthermore, according to the present invention, the reaction can be stopped at the stage of producing a precursor for the silicon nitride sintered body without producing a complete silicon nitride sintered body from the beginning, so the reaction time is also shortened. The significance of the present invention is extremely great as it is capable of doing the following.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example After the entire equipment system as shown in FIG.
Silane gas was introduced into the vacuum reaction vessel 7 from the ammonia cylinder 2 through the flow meter 4, and ammonia gas was introduced from the ammonia cylinder 2 through the flow meter 4.

While monitoring the degree of vacuum in the reaction vessel 7 with a vacuum gauge 8 and maintaining the desired pressure by operating the main valve 10, the electrode 6 is controlled by a high-voltage power source 5 (for example, DC or AC, or a high-frequency oscillator, etc.). A voltage was applied between them to generate glow discharge.

As a result, the silane gas and the ammonia gas reacted, and a silicon nitride precursor was deposited on the screen 9 . Unreacted gas was removed by a scrubber 12.

1 Table 1 shows the composition ratios of the silicon nitride precursors obtained under various experimental conditions.

The silicon nitride precursor thus obtained was pressure-molded and then fired at 1800° C. in a nitrogen atmosphere at 2 atm for one hour to obtain a sintered silicon nitride body. The high temperature strength etc. of the obtained silicon nitride sintered body were extremely satisfactory.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the entire equipment system. Codes 1 and 2 in the figure
3 and 4 represent a silane cylinder and an ammonia cylinder, respectively, 5 is a high-voltage power supply, 6 is an electrode, 7 is a vacuum reaction vessel, 8 is a vacuum needle, 9 is a screen, 10 is a main valve, and 11 is an oil A rotary pump, 12 represents a scrubber. Patent Applicant Toa Fuel Industry Co., Ltd. Agent Patent Attorney Taki 1) Qing Hui Yue 4 Moe 9 Fu Seishi (Holi) February 28, 1981 Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, η9 Cow Conversion Patent in 1982 Application No. 159354 2, Title of the invention 3, Relationship with the case of the person making the amendment Patent applicant Hitocho Choda Address 1-1-1, Tsuhashi, Chiyoda-ku, Tokyo Name Toa Fuel Industry Oudosha 4, 2 people per 41 workers 6. Number of inventions increased by amendment None 7. Application and specification subject to amendment 8. Contents of amendment Engraving of application and specification (no change in content) 37-

Claims (1)

[Scope of Claims] 1) A fine powder produced by reacting a silicon compound selected from silicon hydride or silicon halide, or a mixture thereof, with a nitrogen hydrogenation compound in a plasma atmosphere, , each particle of the fine powder contains hydrogen, and the overall composition ratio of nitrogen and silicon is Si3N (4-x),
A precursor for a silicon nitride sintered body, characterized in that it has a non-stoichiometric ratio expressed by (x>O). 2) A precursor for a silicon nitride sintered body according to claim 1, characterized in that its composition ratio is represented by the general formula Si3N (4-x)Hz. 3) A precursor for a silicon nitride sintered body according to claim 1 or 2, wherein the particle size is 100 to 5000A. 4) A precursor for a silicon nitride sintered body according to claim 1 or 2, wherein the particle size is 100 to 500A. 5) A fine powder produced by reacting a silicon compound selected from silicon hydride or silicon halide, or a mixture thereof and a hydrogen compound of nitrogen in a plasma atmosphere, wherein each particle of the fine powder is Contains hydrogen, and the overall composition ratio of nitrogen and silicon is Si3N (4-x), (x
> O) A silicon nitride sintered body characterized in that a precursor material for a silicon nitride sintered body having a non-stoichiometric ratio is pressure-molded and fired in a nitrogen atmosphere. manufacturing method. 6) The method for producing a silicon nitride sintered body according to claim 5, which comprises pressurizing nitrogen during firing. 7) Small amounts of halogen and oxygen as reaction accelerators during firing
- The method for producing a silicon nitride sintered body according to claim 6, characterized in that any one of nitrogen oxide, nitrogen dioxide, or ammonia, or a mixed gas of two or more thereof is added.