JPS60251928A - Preparation of ultra-fine metal compound particle - Google Patents

Abstract

PURPOSE:To achieve the continuation of a process and to uniformize the particle size distribution of formed fine particles, by injecting a geseous mixture consisting of metal chloride vapor and the other element constituting an ultra-fine metal compound particles from a fan-shaped nozzle before heating the same at specific temp. CONSTITUTION:A high purity silicon metal powder having an average particle size of about 100mum is thrown in a first reaction vessel 1 and a vacuum pump 20 is operated to evacuate a first reaction chamber 2, a separation chamber 7 and a second reaction chamber 8 to 1.3X10<-5>atm. A valve 22 is opened to introduce hydrogen chloride gas into the reaction chamber 2 from a condenser 21 and the reaction chamber 2 is heated to about 1,400 deg.C by a graphite heater 3 to generate silicon tetrachloride gas and hydrogen gas. At the same time, when the vacuum pump 20 is operated to adjust the pressure ratio of the reaction chamber 2 and the separation chamber 7 to 10:1, a mixture of silicon tetrachloride and hydrogen is injected into the separation chamber 7 through a fan-shaped nozzle 4 operated under a deficient inflation condition.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for producing ultrafine metal compound particles.

[Prior art]

Ultrafine metal compound particles are important as raw materials for pigments, abrasives, solid 1Il lubricants, various pastes, and sintered bodies. Among these, when used as a raw material for a sintered body, the driving force for sintering is the surface energy of the particles, so the finer the raw material powder, the higher the sintering speed. For this reason, miniaturization of raw materials is considered to be extremely effective in producing sintered bodies of materials with covalent bonds and low sinterability, such as silicon nitride (Sl)N4) and silicon carbide (S i C). There is.

Conventionally, methods for producing ultrafine metal compound particles include:
There are solid-phase reaction methods, thermal decomposition methods, gas-phase reaction methods, etc. Among these, the gas-phase reaction method is superior to other methods because (a) the raw material is volatile and purification is easy, and the resulting powder can be easily pulverized. Since the product is unnecessary, the product is highly pure, fb) There is little aggregation of the produced particles, (C1
Depending on the reaction conditions, ultrafine particles with a narrow particle size distribution can be easily produced by iM.
It has the characteristics that the atmosphere can be easily controlled, and it can be applied not only to oxides but also to non-oxides such as metals, nitrides, carbides, and boron, which are difficult to synthesize directly by other methods.

For this reason, a method of producing ultrafine metal compound particles from a gas phase is attracting attention.

A method for producing ultrafine metal compound particles by this conventional gas phase reaction will be explained using silicon nitride as an example. The production of silicon nitride involves, for example, silicon tetrachloride (silicon tetrachloride) heated to high temperature.
Sick, ) and ammonia gas are introduced into the reaction vessel,
Mix rapidly in a reaction vessel and react at 1000°C to 1500°C. The formula for this reaction is as follows.

3SiCβ&+4NH, →Si+Na +12HC6(
"Chemical Engineering J, October 1982, Vol. 2 [Manufacture of fine powder materials and surface modification technology"] By the way, in the production of silicon nitride, silicon tetrachloride, which is a metal chloride, is used as a metal and a chloride alone. There is a problem in that it is extremely expensive (at least 10 times more expensive than when it is used alone) and significantly increases manufacturing costs.

In addition, because the reaction in the high-temperature reaction vessel cannot be sufficiently controlled, the particle size distribution of the obtained ultrafine metal compound particles is 100%.
There is a problem that the number of people varies from 1,000 to 1,000 people, and the variation becomes large.

[Purpose of the invention]

The present invention has been made to solve the problems of the prior art described above, and an object of the present invention is to form a metal chloride starting from a metal powder in a method for producing ultrafine metal compound particles, and to form a metal chloride by starting from a metal powder. By continuously performing the steps of reacting the metal compound with the reaction gas, the purpose is to reduce costs and make the particle size distribution of the obtained ultrafine metal compound particles uniform.

[Structure of the invention]

According to the present invention, this object is achieved by the following method for producing ultrafine metal compound particles.

That is, in the method for producing ultrafine metal compound particles of the present invention, at least one metal powder constituting ultrafine metal compound particles and a chlorine-containing gas are heated to a temperature higher than the reaction temperature in a closed container, and the resulting metal chloride vapor is heated. It is instantaneously cooled to a predetermined temperature through a diverging nozzle that operates under underexpansion conditions, and
The metal chloride vapor is separated from other component gases, then this metal chloride vapor is mixed with other elements constituting ultrafine metal compound particles or a reaction gas containing other elements, and the resulting mixed gas is passed through a capillary. Alternatively, the method is characterized in that ultrafine intermetallic compound particles are produced by ejecting the mixed gas at a constant speed through a wide-spread nozzle and heating the mixed gas to a temperature higher than the synthesis temperature of ultrafine metal compound particles.

In the present invention, silicon, aluminum, titanium, zirconium, etc., or a combination thereof can be used as the metal constituting a part of the ultrafine metal compound particles.

Hydrogen chloride or the like can be used as the gas containing chlorine.

Further, as other elements, nitrogen, carbon, oxygen, etc. can be used, and as gases containing other elements, for example, when the other element is nitrogen, ammonia etc. can be used, and when the other element is carbon, for example, ammonia etc. can be used. In this case, lower aliphatic hydrocarbons such as methane, ethane, and propane can be used.

In the present invention, the metal chloride vapor is passed through a diverging nozzle operating under underexpansion conditions in order to separate the metal chloride vapor from other component gases. In other words, the mixed gas ejected under underexpansion conditions has a different ejection angle depending on the specific heat ratio of each element in the mixed gas, and by using this difference in ejection angle,
It is known that it is possible to separate more than one species of gas (for example, Japanese Patent Publication No. 54-4792). This principle can be used to separate the required metal chloride vapor.

Passing the mixed gas of the obtained metal chloride vapor and other elements constituting the metal compound ultrafine particles or a reaction gas containing other elements through a wide-spread nozzle or thin tube is to keep the flow rate of the mixed gas constant and carry out the reaction. This is to control and obtain ultrafine metal compound particles with a uniform particle size.

[Action of the invention]

According to the method for producing ultrafine metal compound particles of the present invention, metal powder and chlorine-containing gas are first heated above the reaction temperature in a closed container, and metal chloride vapor and other component gases (e.g., hydrogen gas) are mixed. Gas is produced. This gas mixture is directed to a diverging nozzle which operates under underexpansion conditions and is ejected through this diverging nozzle. At this time, the metal chloride vapor is separated by utilizing the fact that the ejection angle is different due to the difference in specific heat ratio between the metal chloride vapor and other component gases. Mixing the separated metal chloride vapor with other elements constituting ultrafine metal compound particles or a reaction gas containing other elements,
The obtained mixed gas is ejected at a constant rate through a thin tube or a diverging nozzle into a chamber heated to a temperature higher than the synthesis temperature of ultrafine metal compound particles. As a result, predetermined ultrafine metal compound particles are obtained.

(Effects of the Invention) As described above, the method for producing ultrafine metal compound particles of the present invention provides the following effects.

(b) The method uses inexpensive metal powder and chlorine-containing gas as starting materials and generates metal chlorides during the reaction, without using expensive metal chlorides, resulting in lower costs than conventional methods. It is possible to aim for

(b) Since the mixed gas of metal chloride vapor and other elements or reaction gases containing other elements is guided into the reaction chamber through a thin tube or the like, the flow rate of the mixed gas can be controlled to be almost constant. Therefore, the particle size distribution of the obtained ultrafine metal compound particles becomes more uniform than that obtained by conventional methods.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. This example shows an example of manufacturing silicon nitride.

Here, FIG. 1 is a schematic configuration diagram showing an outline of an apparatus for producing ultrafine metal compound particles used in an example of the present invention.

In the figure, reference numeral 1 denotes a substantially sealed first reaction container that is partially openable and closable, and has a first reaction chamber 2 formed therein. A first graphite heater 3 is installed around the first reaction vessel 1, and the temperature of the first reaction chamber 2 can be controlled to a predetermined temperature by the first graphite heater 3. The first reaction vessel 1 is connected to a second reaction vessel 5 via a diverging nozzle (Laval tube) 4, and the second reaction vessel 5 is connected to a separation chamber 7 via a thin tube 6.
and a second reaction chamber 8. A mixed gas sampling tube 9 that penetrates the second reaction vessel 5 and is bent is installed in this separation chamber 7, and one end of this mixed gas sampling tube 9 is
It is provided at a position facing the diverging nozzle 4 in the separation chamber 7, and the other end is connected to the pump 11 via a valve 10 outside the second reaction vessel 5. This pump 11 is connected to a cooling pipe 12. Further, an ammonia gas supply pipe 13 is opened in the middle of this separation chamber 7, and ammonia gas as another element is introduced through this ammonia gas supply pipe 13. Further, a second graphite heater 14 is attached around the second reaction chamber 8 in order to maintain the inside of the second reaction chamber 8 at a predetermined temperature.

The second reaction chamber 8 communicates with the cyclone 16 via a conduit 15. This cyclone 16 has valve 1 below.
It is possible to take out the produced ultrafine particles through 7, and the upper part is connected to a condenser 21 through a conduit 18, a valve 19, and a vacuum pump 20. A part of the components condensed in this condenser 21 is connected to the first reaction vessel 1 via a conduit 23 having a valve 22 in the middle,
Other components are taken out of the system via valve 24. Furthermore, a conduit 26 having a valve 25 in the middle is connected to the conduit 23 in order to reuse silicon tetrachloride.

Next, the operation of this embodiment will be explained.

First, high-purity silicon metal powder with an average particle size of about 100 μm is charged into the first reaction chamber 1, and the vacuum pump 20 is operated to remove the first reaction chamber 2, separation chamber 7, and second reaction chamber 8. and 10-' Torr (1,3
x 10-” atmosphere). Then, valve 22
is opened, hydrogen chloride gas is introduced into the first reaction chamber 2 from the condenser 21 via the conduit 23, and the inside of the first reaction chamber 2 is heated to a temperature below the melting point of silicon metal, that is, approximately Heat to 1400°C. Then, silicon metal and hydrogen chloride gas react as shown in the following equation to generate silicon tetrachloride gas and hydrogen gas.

Si (solid) + 4HCj! (gas)-3iCβ4 (
Gas) +2H+ (Gas) The pressure inside the first reaction chamber 2 reaches several hundred Torr due to the silicon tetrachloride gas and hydrogen gas generated by the above reaction. Simultaneously with this reaction, the vacuum pump 20 is operated to control the pressure in the separation chamber 7 and the second reaction chamber 8 while adjusting the opening degree of the valve 19. In this example, the pressure ratio between the first reaction chamber 2 and the separation chamber 7 was adjusted to approximately 10=1. As a result, a mixed gas of silicon tetrachloride and hydrogen is ejected into the separation chamber 7 through the diverging nozzle 4 which operates under underexpansion conditions.

The ejected mixed gas causes a rapid temperature drop due to adiabatic expansion, reaching approximately 700°C.

At this time, since the mixed gas ejected under underexpansion conditions has different ejection angles depending on the specific heat ratio of each element in the mixed gas, it is possible to separate the gases by utilizing the difference in ejection angles. In the case of this example, silicon tetrachloride gas (specific heat ratio: 1.13) flows in the outer part of the underexpanded flow, and a mixed gas of silicon tetrachloride gas and hydrogen gas (specific heat ratio: 1.41) flows in the inner part. flows.

Therefore, by arranging the tip of the mixed gas sampling pipe 9 immediately after the wide-spread nozzle 4 along the boundary line between the silicon tetrachloride gas and the mixed gas of silicon tetrachloride and hydrogen, the mixed gas of silicon tetrachloride and hydrogen can be The silicon tetrachloride gas is collected into the mixed gas collection pipe 9 and diffused into the separation chamber 7 .

The mixed gas collected in the mixed gas sampling pipe 9 is transferred to the pump 11.
The hydrogen gas is introduced into the cooling pipe 12, where it is cooled to room temperature and separated into silicon tetrachloride and hydrogen gas, and the hydrogen gas is taken out of the system via the valve 27. Further, the liquefied silicon tetrachloride is sent to one of the reaction chambers 2 as appropriate through the conduit 26 by the valve 25 and reused.

On the other hand, silicon tetrachloride gas flowing in the outer part of the underexpanded flow is mixed with ammonia gas introduced through the ammonia gas supply pipe 13 in the separation chamber 7, and reacts as shown in the following equation to produce silicon imide. .

5i (14+8NH] → 4NHa C1! +S i (NH2).

The gas containing silicon imide is introduced into the second reaction chamber 8 at a substantially constant rate through a thin tube 6 having a diameter larger than that of the diverging nozzle 4. At this time, the pressure ratio between the separation chamber 7 and the second reaction chamber 8 is set to about 1.5:1. The gas flow introduced into the second reaction chamber 8 is heated to 1000° C. to 1600° C. by the second graphite heater 14, and silicon imide is thermally decomposed to produce silicon nitride. At this time, the higher the heating temperature (and the longer the decomposition time), the more grains of the obtained silicon nitride powder grow and become coarser.

After pyrolysis, the gas stream becomes a mixture of hydrogen chloride, nitrogen, and hydrogen containing silicon nitride (solid). This mixed gas is
Through a conduit 15 it is led to a cyclone 16 in which the silicon nitride powder is recovered via a valve 17. The remaining mixed gas passes through conduit 18 to condenser 21
Here, it is separated into a mixed gas of nitrogen and hydrogen and liquefied hydrogen chloride. The mixed gas of nitrogen and hydrogen is then taken out of the system via the valve 24. On the other hand, the liquefied hydrogen chloride is guided to the first reaction chamber 2 through the conduit 23 by opening and closing the valve 22 as necessary, and is reused.

The resulting ultrafine silicon nitride particles were amorphous when the temperature of the second reaction chamber was 1000°C to 1200°C, and had a uniform particle size of about 500°C. In addition, the temperature inside the second reaction chamber was set to 1200°C to 1200°C.
At 400°C, the particle size of 1000 particles is uniform
-3i,N, was obtained, and the temperature in the second reaction chamber was reduced to 140
When the temperature was 0°C to 1600°C, uniform β-3i and N4 with a particle size of 1000 were obtained.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and includes various embodiments within the scope of the claims. .

For example, although an example of producing ultrafine silicon nitride particles has been shown in the embodiment, other nitrides and oxides can also be produced in a similar manner.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the outline of an apparatus for producing ultrafine metal compound particles used in Examples of the present invention. 1 - First reaction vessel 2 ---- First reaction chamber 3 - First graphite heater 4 ---- One wide-ended tube 5 ---- Second reaction vessel 6 ---- Thin tube 7 --- One separation chamber 8 --- Second reaction chamber 9 --- One -- Mixed gas sampling tube 10.17.19.22.24.25.27 ---
- Harb 11 ------- Pump 12 ---- - Cooling pipe 13 ------- Ammonia gas supply pipe 14 ----
-Second graphite heater 15.18.23.26-
--- Conduit 16 --- Cyclone 20 --- - Vacuum pump 21 --- Condenser Fig. 1

Claims (1)

[Claims] (11) At least one metal powder constituting ultrafine metal compound particles and a chlorine-containing gas are heated to a temperature higher than the reaction temperature in a closed container, and the resulting metal chloride vapor is passed instantaneously through a wide-spread nozzle that operates under underexpansion conditions. At the same time as cooling to a predetermined temperature, the metal chloride vapor is separated from other component gases, and then this metal chloride vapor is mixed with other elements constituting ultrafine metal compound particles or a reaction gas containing other elements. ,
A method of producing ultrafine metal compound particles, characterized in that the obtained mixed gas is ejected at a constant speed through a narrow tube or a wide-spread nozzle, and the mixed gas is heated to a temperature higher than the synthesis temperature of ultrafine metal compound particles to produce ultrafine metal compound particles. Production method.