JPS60251108A - Device for preparing silicon nitride powder - Google Patents

Abstract

PURPOSE:To obtain Si3N4 powder with satisfactorily sintered condition and high content of fine alpha-phase by allowing a specified mixture of starting materials to react in a reaction vessel in a fluidized condition using a nonoxidizing gas contg. hot N2. CONSTITUTION:Powder mixture of starting materials consisting of 1pt.wt. powdery SiO2, 0.4-4pts.wt. carbon black, and 0.05-1pt.wt. Si3N4 is granulated to particles having 0.2-30mm. minor axis. The granulated particles are fed from a starting material hopper 14 to a reaction chamber 1a in a reaction vessel 1 made of carbon. On one hand, gaseous N2 is fed through a pipe 29 to a passage 3 between the vessel 1 and a quartz glass tube 2, heated in the midway of the passage 3 and in the preheating zone 31 at the bottom of the reaction chamber 1a at 1,300-1,550 deg.C by an induction heating coil 4, and ejected into the chamber 1a to cause fluidization of the granulated particles and reduction and nitridation reaction. Then, unreacted gaseous N2 and produced gaseous CO, etc. are discharged from a gas discharging port 13, and the reaction product is drawn by pulling a valve 20 toward downward. Thereafter, remaining C is removed by burning in the air at 700 deg.C. By this method, Si3N4 having 0.2-1.4mu particle size having low content of unreacted product or by-product is obtd.

Description

[Detailed description of the invention] The present invention relates to an apparatus for producing silicon nitride powder.

For example, silicon nitride - yttrium oxide or magnesium oxide (within S -Y2O or Si 3 N4
-Mo O) Sintered bodies have high mechanical strength and excellent heat resistance, so they are being applied to high-temperature gas turbine components and the like.

The mechanical properties of the sintered silicon nitride yarn are greatly influenced by the properties of the starting materials, and it is desired that the α-phase content of silicon nitride be as high as possible.

Conventionally, silicon nitride-based powders have been manufactured using various methods, but recently, a method to obtain silicon nitride powder with a high α phase rejection rate is to use silica powder, carbon powder, silicon nitride powder, and silicon carbide. A method has been adopted in which a mixed raw material powder is prepared by adding at least one of a powder and a silicon oxynitride-based powder, and the mixed raw material powder is heat-treated in a nitrogen-containing non-oxidizing atmosphere to perform a reduction/nitriding reaction.

However, conventional methods have various drawbacks as described below.

(1) Silicon nitride grows on the surface using the added powder such as silicon nitride in the mixed raw material powder as a core, so in order to obtain fine silicon nitride powder with good sinterability, it is necessary to add The amount of powder added must be increased. When the amount added is increased in this way, the particle size of the silicon nitride powder produced becomes uniform, and the compacting density during compacting becomes low.

(2) In the reaction that generates Si3'N4 from SiO2 and C, the solid-solid reaction between 3i0+ and C is the rate-determining step.
Good contact between silica powder and carbon powder is required. However, all of the starting materials are fine powders, and the bulk specific gravity of the mixed raw material powder is extremely small<o, i3~0.
20) It is difficult to obtain a good contact state between silica particles and carbon particles. Furthermore, since the amount of filling is small, production efficiency is poor.

(3) When filling mixed raw material powder into a container and performing a reduction/nitriding reaction, the starting raw material is fine even though the bulk specific gravity of mixed raw material powder is small, so the gaps in the powder bed are very narrow. is in a state. Therefore, the CO gas generated by the reaction is difficult to diffuse out of the powder bed, and the N2 gas necessary for the nitriding reaction is difficult to penetrate into the powder bed. In this case, inside the Iq-integrated bed where the powder bed is thick, the N2m degree is low and the COm degree is high, so one SiC or Si2ON2 is produced as a by-product, or unreacted SiO2 remains, and -
8i 3 N4 production is not good. Therefore, the thickness of the powder bed is limited to about 1,511,111 mm.

In addition, since the reaction rate inside the powder bed is slow, Si3N4
It takes a lot of time to complete the generation and the production efficiency is low.

The present invention has been made to solve the above-mentioned drawbacks, and by granulating mixed raw material powder and reacting the granulated particles in a fluidized bed state, it is possible to improve production efficiency and improve production efficiency. The object of the present invention is to provide an apparatus capable of producing fine silicon nitride powder having a high α phase content and having good sinterability.

The gist of the present invention to achieve this purpose is to provide an open part for supplying raw materials at the top of a reaction vessel made of carbon, and provide a reaction chamber in the thick part of the reaction vessel.
The outer periphery of the reaction vessel is surrounded by a quartz glass tube, a space is formed between the reaction vessel and the tube to create an annular passage, the passage is connected to the porous hole at the bottom of the reaction vessel, and a An induction heating coil is placed at a corresponding position in the reaction chamber, and the coil generates heat in the reaction chamber to heat the reaction chamber. At the same time, a nitrogen-containing non-oxidizing gas is heated in the middle of the passage, and the gas is preheated. An apparatus for producing silicon nitride powder is characterized in that the silicon nitride powder is heated in a region and then supplied to a reaction chamber in the reaction container through a porous hole in the lower part of the reaction container.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, a reaction vessel 1 made of carbon has an open upper part (a lower part has porous holes and an outer periphery is surrounded by a tube 2 made of quartz glass).A reaction chamber 1a is located below the reaction vessel 1. An annular space is formed between the reaction vessel 1 and the duplex 2, and a passage 3 for supplying nitrogen-containing non-oxidizing gas (hereinafter simply referred to as nitrogen gas) is formed in the thick part. This passage 3 communicates with the reaction chamber 1a inside the reaction container 1 via a porous hole in the bottom of the reaction container 1.

The induction heating coil 4 is used to simultaneously heat the reaction chamber 1a in the reaction container 1 and the middle of the passage 3 outside the reaction chamber 1 by generating heat in the reaction container 1. The thickest part of the reaction vessel 1 becomes the hottest. A high frequency oscillator 5 connected to the coil 4 is controlled by a control panel 6 to adjust the heating temperature by the coil 4.

Nitrogen gas passes through the flow meter 8.9 from the pipe 29 to the passage 3.
flows into the upper part of the Also, a part of the nitrogen gas is transferred to the flowmeter 10.
1, 11, and 12 into a raw material hopper 14 above the reaction vessel 1, a lower part 15 of the reaction vessel 1, and a pipe 16, respectively.

The raw material hopper 14 is connected to the exhaust port 13, so that the raw material is supplied into the reaction chamber 1 from the waste port 13 at the upper part of the reaction vessel 1.

A pulp 20 is provided below the reaction vessel 1, and the reaction product can be taken out from the outlet 15 by opening the valve as necessary.

One end of the pipe 21 is connected to an exhaust gas 113, and the other end is connected to an atmosphere analyzer (not shown).

One end of the pipe 22 is connected to the dust collection case 23, and the other end is connected to a dust collector (not shown).

At the lower end of 1-72, there is a water cooling diode 11 tat 25, respectively.
．． 26 are provided. Reference numerals 25a and 26a indicate the cooling unit [1], and 25b126b indicates a water cooling water outlet. In the lower part of the reaction vessel 1, a plurality of fins 30 are provided alternately to form a preheating region 31.

A porous member 3 such as a perforated plate is provided at the bottom of the reaction chamber 1a of the reaction container 1.
2 is a provision.

Further, a plurality of heat insulating plates 33 and partition plates 33 are installed below the tube 2.

Reference numeral 35 is a nitrogen gas outlet.

Before explaining the operation of such manufacturing equipment, first,
The raw materials to be put into the raw material hopper 14 will be explained.

The mixing ratio of the three component powders used as starting materials varies depending on the type of the component powders, but for example, silica-carbon silicon nitride (SiO2-C-8i 3 N4)
In the case of a mixed system, SiO2:C:Si3N4 =1
:0.4~4;0°005·~1.0 is preferable. If ', then C for 1 of SiO2
is less than 0.4, 5i02 remains unreacted and a large amount of Si 2 ON2 is produced.
3 The amount of N4 produced decreases.

Moreover, if C exceeds 4, the formation of β-phase Si 3 N4 is observed, and as a result, the purity of α-phase Si 3 N4 deteriorates, and in particular, a decrease in yield is observed. On the other hand 51
If Si 3 N4 is less than 0.005 with respect to 1 of 02, the yield effect of α-phase Si 3 N4 will be small, and if it exceeds 1, a powder with preferable powder characteristics will not be obtained.

Examples of the method for preparing a mixed powder raw material by mixing starting materials include a wet or dry boil mill method.

The mixed raw material powder may be granulated by a wet method using water, alcohol, etc., followed by drying and granulation, or may be granulated by a wet method using water, alcohol, etc., or by drying and granulating. Drying and granulation may be performed using an inorganic binder such as silicate or colloidal silica. In addition, granulation methods include wet or dry extrusion methods, rotation methods, pressure compression methods, fluidized bed granulation methods 2, centrifugal flow methods, agitation granulation methods, spray dry hair no methods, etc., or combinations thereof. can be given. By granulating the mixed raw material powder, the contact state between SiO2 and C is improved, and Si
3 In the rate-determining step of the N4 production reaction, a solid reaction between 4[5iOz and C becomes more likely to occur. Inside the granulated particles, S
SiO gas and Co gas generated by the reaction of iO2 and C cause cracks in the particles. Co gas diffuses to the outside through these cracks, and N2 gas permeates inside, making it easier for reactions to occur, thereby improving Si 3 N 4 production efficiency.

The reason why the breadth of the granulated particles is in the range of 0.2 to 30n+n+ is because if it is less than 0.2 mm, the granulated particles will be easily scattered by the gas flow and a stable fluidized bed state will not be obtained.
This is because if it exceeds 3Q+++m, it becomes difficult for Co gas to diffuse from inside the granulated particles and for N2 gas to penetrate into the inside, and the reaction does not proceed well.

In addition, by reacting such granulated particles in a fluidized bed state, the temperature of the reaction system is made uniform, the diffusion of Co gas and the penetration of N2 gas are improved, and the throughput of granulated particles can be increased. As a result, production efficiency can be further improved.

Note that the nitrogen-containing non-oxidizing gas in the present invention includes:
Examples include N2, NH3, N2-to-12, N2-inert gas, and the like.

This is because it is difficult to produce nitrogen-containing non-oxidizing material in the reaction chamber 1a, and if the temperature exceeds 1550°C, the formation of SiC is observed.

Next, a method for manufacturing silicon nitride powder using the manufacturing apparatus shown in FIGS. 1 and 2 will be briefly described.

First, 0.1 part by weight of silicon nitride powder was added to 1 part by weight of silica powder and 0.5 parts by weight of carbon black to prepare a mixed raw material powder, and this mixed raw material powder was granulated to a width of 3IIIR. Next, the powdered particles were fed into the reaction chamber 1a of the reaction vessel 1 from the raw material hopper 14 of the illustrated manufacturing apparatus. How to use: After heating with sakaki 31 from pipe 29 into passage 3, high-temperature nitrogen gas is ejected into reaction chamber 1, and the granulated particles in reaction chamber 1a are brought into a fluidized bed state to perform a reduction/nitriding reaction. went.

At this time, the temperature inside the reaction chamber was about 1450°C. Waste residues such as unreacted nitrogen gas and generated Co gas were discharged from the gas exhaust port 13, and the 3° reaction products were taken out from the outlet 15 by pulling the valve 20 downward to open it.

After this, the reaction product was heat-treated in air at 700°C,
The residual carbon was removed by combustion to obtain a silicon nitride powder product.

In this way, the reaction time can be shortened, the throughput can be increased, and production efficiency can be improved.

In addition, since the reaction proceeds uniformly, the homogeneous range is 0.2~
The average particle size was 1.4 am and 0.7 μm. That is, since the powder was fine and had a wide particle size range, Si3N4 powder had a high compaction density and good sinterability. Also, S
No IC was detected.

, I and 1 fertilizer production equipment heats nitrogen gas in the heating chamber 1a, and there is no need to provide a heat source in the furnace.
It has a simple structure.

Furthermore, the heat of the exhaust gas from the reaction vessel 1 can also be used as residual heat for the nitrogen-containing non-oxidizing gas.

According to the present invention, as described above, it is possible to improve production efficiency and produce a fine silicon nitride powder having a high content of zero layers and having good sinterability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a bench scale fluidized bed system to which the present invention is applied, and FIG. 2 is a vertical sectional view showing a silicon nitride powder manufacturing apparatus. 1...Reaction vessel 2...Tube 3...Passage 4...] Iru Patent applicant Director of the Agency of Industrial Science and Technology Kawa 1) Yube Figure 1

Claims (1)

[Claims] An open part for supplying raw materials is provided at the top of the carbon reaction vessel, and a reaction chamber is provided in the thick part of the reaction vessel.
The outer periphery of the reaction vessel is surrounded by a quartz glass tube, a space is formed between the reaction vessel and the tube to create an annular passage, the passage is connected to the porous hole at the bottom of the reaction vessel, and a An induction heating coil is placed at a corresponding position in the reaction chamber, and the coil generates heat in the reaction vessel to heat the reaction chamber. 1. An apparatus for producing silicon nitride powder, characterized in that the silicon nitride powder is heated in a preheating region and then supplied to a reaction chamber in the reaction container through porous holes in the lower part of the reaction container.