JPS603033B2 - Silicon nitride manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing nitride silicate, namely Si3N4.

It is known, for example, from Taruko Sho 47-14125 and other publications, that silicon nitride can be obtained by the so-called spark isostatic press method, in which Si powder is subjected to pressurized discharge scaling while being brought into contact with high-pressure N2 gas. .

Furthermore, a technique for obtaining boron nitride by mixing Si powder and a nitrogen-containing substance such as Fe2N3, BN, N, etc. and performing discharge condensation is also disclosed in Hakama Kosho 49-Shigema No. 2.

However, these known methods use Si as a starting material. On the other hand, although Si exists in large quantities in the earth's crust,
It is not produced in a free state, but mainly as an oxide or citrate. Therefore, for example, SiQ
The conventional method of reducing Si to obtain Si and nitriding it in the manner described above to obtain S3N4 is a roundabout method and is not rational. Although Si3N4 is widely available as sand at a low price, it cannot be said that the Si3N4 obtained by the above method is necessarily cheap.

In addition, as another method for producing hydrogenated carbide, an amorphous carbon powder having an oil absorption amount of 100'/100 ta or more is used, and the weight ratio is the above amorphous carbon powder/
Silica powder is 0. Hakama Sekisho No. 52-90499 describes a technique in which the mixed raw materials are blended so as to have a vowel or more, and then heated at high temperature while supplying nitrogen-containing non-oxidizing gas to condense the mixed raw materials into fists. Disclosed.

However, the above-mentioned method has a problem in that efficiency is low and production costs are high because only the desired product can be obtained despite the labor and time required for production.

The present invention was made based on the idea of a superior horse,
The purpose of this invention is to provide a method for manufacturing oxidized silicon in large quantities in a short period of time at low cost.

The above purpose is achieved by pressurizing a mixture of silicon oxide and carbon powder in a weight ratio of about 10:4 in a mold with air permeability, and forcing nitriding gas into the mixture. This is achieved by performing discharge phosphorization while infiltrating the

Therefore, when carrying out electrical discharge of metal or alloy powder, a breathable mold is used, the powder to be competitively streaked is filled into the mold, and a pressing body/uniform electrode is placed in the mold with light compression pressure. At the same time, the powder is brought into contact with a high pressure gas flowing from the outside of the mold into the inside of the mold, and then electricity is applied to the powder to perform interparticle discharge and Joule heat heating. The technology and equipment for dispersing the
It is disclosed in No. 3732 and is well known.

Therefore, in the present invention, a device similar to this device is used, but when carrying out the method of the present invention,
Because a high-level chemical reaction takes place inside the mold, a small amount of silicon nitride is not produced only on the surface layer such as the side surface of the Akatsuki formed body, but instead a large amount of high-quality, dense boron nitride lumps are obtained. It is something that can be done. The present invention will be explained below with reference to drawings and examples.

The drawing is an explanatory view showing one embodiment of the apparatus used to carry out the present invention, in which 1 is a heat-resistant cylindrical die for competitive silk made of air-permeable graphite, 2 is a vacuum tank, and 3 is a 1 is a nitrogen gas tank, 4 and 5 are insulating pushers, 6 and 7 are a pair of energized pseudo-stripe punches each consisting of delicate parts 6a, 7a and porous parts 6b, 7b, and 8 and 9 are hydraulic units (not shown). 10 and 11 are pistons, 12 and 13 are connecting rods, 14
and 15 is an insulating gasket, 16, 16 is a bolt, 1
7 is a mixture of silicon oxide powder and carbon powder, 18 is an orthogonal hybrid power source for current sintering, 19 is a switch, 20 is a nitrogen gas cylinder, 21 is a vacuum pump, and 22 and 23 are stop valves.

Therefore, when trying to obtain high purity Si3N4 that does not contain Sj02 etc., it is recommended that the blending ratio of Si02 and C in the mixture 17 is 2 moles of C to 1 mole of Si02. This blending ratio is approximately 60:24 by weight.
It is. Cinnamon sand with a particle size of 40 French or less is used as Si02, and petroleum coke with a particle size of 20 French or less is used as C. These are mixed uniformly, filled between the punches 2 and 3 inside the die 1, and lightly compressed under a pressure of about 100 kg' or less.

Each half of the punches 6 and 7, i.e. the portion 6 that communicates with the vacuum chamber 2 or the nitrogen gas chamber 3 from the side that compresses the mixture 17, respectively;
b and 7b are made of an air-permeable conductive material such as porous graphite, and the remaining halves 6a and 7a are made of a dense conductive material.

Nitrogen gas at a predetermined pressure is introduced into the nitrogen gas tank 3 from a nitrogen gas cylinder 20, and the inside of the vacuum tank 2 is evacuated and depressurized by a vacuum pump 21.

Therefore, the nitrogen gas in the nitrogen gas tank 3 passes through the porous part 7b of the punch 7, the mixture 17 and the porous part 6b of the punch 6, or the die 1, and diffuses in the side direction of the vacuum tank 2 or the die 1. , will be distributed. In this state, when the switch 19 is turned on, a pulsed pulsating current in which alternating current and direct current having a frequency of 200 to 2000 Hz are superimposed at a power ratio of about 1:3 flows through the mixture 17. Although this power source has a voltage of several tens of volts, it has a large capacity and can flow a large current of 200 to 2000 A/ground. Sj02 is an insulator, but carbon is a good conductor, and the above current flows through the die 2 and the carbon powder in the mixture 17, which causes interparticle discharge and Joule heat, causing the key compound to scorch. Since this state occurs and the nitrogen gas is activated, the following chemical reaction occurs in the mixture 17. Si020C→Si010CO Book i○10C+N2→Si20N20CO $i20N213C+N2-$i3N4103CO, and finally $i020 to 12N21 Si3N40 to 0
Si3N4 is obtained by this reaction.

The CO generated by this reaction is collected together with excess N2 in the vacuum chamber 2 and treated or recovered by a device (not shown). This reaction requires about 5 lbs of current
The compression pressure continues for 0.4 to 1 minute, and is almost completed by supplying 2 to 3 times the theoretical value of N2 gas during that period, and then the compression pressure is increased to 0.4 to 1. When it increases to a certain degree and is subjected to strong pressure molding, a dense Si3N4 lump is obtained.

When the compression pressure is lowered to 0.0% or less, porous or even particulate Si3N4 can be obtained.
By adjusting the blending amount of carbon, a mixture of Si20N2, Si02, etc. and Si3 N4 can be obtained.

Next, one embodiment of the present invention will be described. Example Si02 powder with a particle size of 40 mm and petroleum coke with a particle size of 15 mm were mixed in a weight ratio of 10:4, filled into a graphite die with an inner diameter of 8 mm, and lightly crushed under a pressure of 30 k9'. D. while compressing and supplying nitrogen gas. C. 30V×10
00 ship: AC. After supplying power of 30V x 333 ships x 400Hz for 5 minutes, compression molding was carried out at a compression pressure of 0.5T/ground to obtain a dense Si3N4 lump containing 10% SiON2.

Since the present invention is constructed as described above, Si3N4 can be manufactured at extremely low cost when using the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is an illustration showing one embodiment of the apparatus used to carry out the method of the invention.

1...Die, 2...Vacuum chamber, 3...Nitrogen gas tank, 6,7
...Punch, 8,9...Hydraulic cylinder, 17...S
Mixture of i02 and C, 18...Power supply, 20...Nitrogen gas cylinder, 21...Vacuum pump.

Claims (1)

[Claims] 1 A mixture of silicon oxide and carbon powders in a weight ratio of approximately 10:4 is pressurized in an air-permeable mold, and discharge sintering is performed while nitrogen gas is permeated into the mixture to form silicon nitride. A method for producing silicon nitride, characterized in that it obtains silicon nitride.