JPH0127773B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing fine powder of a metal compound, and more specifically, the present invention relates to a method for producing a fine powder of a metal compound, and more particularly, the present invention relates to a method for producing a fine powder of a metal compound, and more specifically, a metal compound is formed by rapidly cooling at least one gaseous metal and other elements constituting the metal compound using a wide-spread nozzle. The present invention relates to a method for producing fine powder. Metal compounds are generally produced from a melt of the metal of which the metal compound is to be made and a gaseous body of other elements. In such a method for producing a metal compound, it is inevitable that impurities are mixed into the produced metal compound, the metal compound cannot be obtained as a fine powder of several micrometers or less, and the metal compound cannot be obtained from a melt. In rapid cooling, the cooling rate is limited to about 10 ⁵ °C/sec, which results in excellent amorphous materials.
There are drawbacks such as the inability to obtain metal compounds with the following characteristics. In addition, so-called vapor phase growth methods and vacuum vapor methods have been put into practical use as methods for manufacturing single crystals or thin films of various metal materials, but these methods utilize gradual vapor deposition on a substrate. However, the metal material obtained is a mixture of an amorphous layer directly above the substrate and a crystalline layer above it, and the production rate is slow, making it unsuitable for mass production. This method is inappropriate as a method for efficiently producing fine powder of a metal compound. In view of the above-mentioned shortcomings of these conventional methods, one method for producing fine powder of silicon nitride, which is particularly used as a raw material for ceramics, is to form a metallic silicon powder and to process the metallic silicon powder. A method has been put into practical use in which powder is heated in a nitrogen or ammonia stream and silicon and nitrogen are combined at a temperature of 1500° C. or lower while controlling the nitrogen gas pressure. However, in this method, the silicon nitride obtained is a mixture of α-type and β-type silicon nitride, and it is difficult to obtain fine silicon nitride powder. has the disadvantage that the raw material, silicon metal, must be ground for a long time. In addition, as another method for producing fine silicon nitride powder, silicon nitride powder is produced by a gas phase reaction between silicon halide and ammonia, or a nitrogen-containing silane compound and ammonia at high temperatures (1000 to 1500°C). A method of manufacturing has been developed. However, in this method, it is inevitable that chlorine, hydrochloric acid, etc. generated by the gas phase reaction will be mixed into the silicon nitride produced.
The obtained silicon nitride powder is a mixture of powders with various particle sizes of 3 μm or less, and the particle size is 1 μm or less.
There is a drawback that post-treatment of pulverization and classification is required in order to obtain the following sized fine powder. In view of the above-mentioned shortcomings in the conventional method for producing metal compound powder, the inventors of the present application,
As a result of various experimental studies, we found that a gaseous mixture of the metal and other elements constituting the metal compound was quenched using a wide-spread nozzle, and they were reacted during the quenching process. It has now been discovered that the various drawbacks of the method described above can be overcome. The present invention is based on the knowledge obtained as a result of various experimental studies conducted by the inventors of the present invention, and is based on the knowledge obtained as a result of various experimental studies conducted by the inventors of the present invention. The purpose is to provide a method that can be manufactured at low cost. According to the present invention, this object is achieved by rapidly cooling a gaseous mixture of at least one metal and another element to be constituted by at least one metal compound by adiabatically expanding it through a diverging nozzle. A method for producing a fine powder of the metal compound by reacting the metal compound with an element, and quenching at least one gaseous metal to constitute one metal compound by adiabatically expanding it through a first diverging nozzle; Further, another element to constitute the metal compound is mixed in a gaseous state, and the mixed gas is adiabatically expanded through a second diverging nozzle to rapidly cool the metal and the other element. This is achieved by a method of producing fine powder of the metal compound by reaction. According to the method for producing fine powder of a metal compound according to the present invention, the metal vapor constituting the gaseous mixture maintains its size in its gaseous state due to self-adiabatic expansion when passing through the diverging nozzle. Because it is rapidly cooled to a solid fine powder and simultaneously reacts with other elements that are to constitute the metal compound, it is possible to obtain a fine powder of a metal compound with an extremely small particle size and a substantially uniform particle size. can. Furthermore, according to the method for producing fine powder of a metal compound according to the present invention, the metal vapor is rapidly and continuously converted from a gas phase to a solid phase by the wide-spread nozzle, so that high-purity metal compound powder can be efficiently produced. Since it can be produced continuously and does not require steps such as crushing and classification as in conventional production methods, fine powder of metal compounds can be produced at low cost. Furthermore, according to the method of the present invention, by appropriately setting the temperature and pressure of the gaseous mixture before and after passing through the wide-spread nozzle, the metal compound can be formed in a desired crystalline form, such as amorphous or α-type. A fine powder can be obtained. Note that the metals and other elements that should constitute the metal compound in the production method according to the present invention may be any combination of metals and elements that combine with each other,
In particular, the metal is preferably silicon, aluminum, titanium, etc., or a combination thereof, and the other elements are nitrogen, carbon, oxygen, or even other metal elements (in this case, the resulting metal compound becomes an intermetallic compound). That's fine. In this case, the other element forming part of the gaseous mixture may be produced not only from a gas consisting of the element itself but also from a substance containing the element and from which the element can be separated. For example, when the other element is nitrogen, not only nitrogen gas but also a substance such as ammonia may be used. Particularly, when producing fine powder of silicon nitride from a mixed gas consisting of metallic silicon vapor and nitrogen gas or nitrogen generating gas such as ammonia, the temperature of the mixed gas before adiabatic expansion by the wide-spread nozzle is substantially 2000°C. ℃ or higher and the pressure is preferably 10 ⁻¹ atm or lower. According to this method, α-type or amorphous silicon nitride fine powder with a particle size of 1 μm or less can be obtained. In addition, in this case, by controlling the temperature of the metal compound to 1000 to 1500°C after adiabatic expansion using the wide-spread nozzle, α-type silicon nitride fine powder with a particle size of substantially 1 μm or less can be produced. Can be done. As described above, the main feature of the method for producing fine powder of a metal compound according to the present invention is that the gas mixture of at least one metal and other elements constituting the metal compound is rapidly cooled and reacted. be. How quenching a gaseous mixture is effective in obtaining extremely fine metal compound powder will be explained with reference to the case of producing fine silicon nitride powder from metal silicon vapor and nitrogen gas. Metallic silicon is a metal that is relatively difficult to vaporize.
0.5Torr (6.6×10 ^-4 atm) even at a temperature of 2000℃
It has an equilibrium vapor pressure of only . Therefore, the method of producing fine powder of silicon nitride using metal silicon vapor obtained by heating metal silicon to a temperature of 2000° C. or higher is not advantageous in terms of thermal energy compared to conventional methods. However, by rapidly cooling the metallic silicon vapor, the metallic silicon is rapidly converted from its vapor state to a solid state. A fine powder of a metal compound that is substantially homogeneous can be obtained. On the other hand, such fine and uniform metal compound powder cannot be obtained using conventional methods that utilize gas phase reactions and the like. That is, metallic silicon and nitrogen gas react at a relatively low temperature of about 900 to 1700 DEG C. to form silicon nitride, and this silicon nitride is stable within the above-mentioned temperature range.
Therefore, for example, when silicon nitride is produced by a gas phase reaction between a metal silicon generated gas (such as silane gas (SiH ₄ )) and a nitrogen generated gas (such as ammonia gas (NH ₃ )) at a temperature of 900 to 1700°C, teeth,
The reaction easily progresses in the direction of the combination of metal silicon and nitrogen gas to form solid silicon nitride, and silicon nitride grains grow and become coarse grains in an extremely short period of time. Next, a description will be given of what kind of cooling means is suitable for rapidly cooling a gaseous mixture of metals and other elements. Conventionally, various cooling methods have been put into practical use as methods for cooling gas. The inventors of the present application have conducted various experimental studies on the optimal cooling method for rapidly cooling a gaseous mixture of metals and other elements to obtain fine powder of a metal compound. Wide end nozzle (Laval nozzle) used as a nozzle for propulsion equipment
is the most effective, and according to the Suehiro nozzle, 10 ⁶ °C/
It has been found that a gaseous mixture can be rapidly cooled at a cooling rate of about sec. In addition, the operating conditions for the diverging nozzle are determined by the ratio of the pressure on the inlet side of the nozzle (stagnation point pressure) and the pressure on the outlet side of the nozzle (back pressure). , proper expansion conditions,
There are three types of overexpansion conditions. When the present inventors rapidly cool a gaseous mixture of a metal and other elements using a wide-divergent nozzle to obtain a fine powder of a metal compound, the inventors of the present application set the wide-divergent nozzle under any of the three operating conditions described above. As a result of various experimental studies, we have conducted various experimental studies on the optimum condition of turbulent flow, i.e., shock waves (first Proper expansion or overexpansion conditions that produce a flow (indicated by the symbol Wi in figure c) and large pressure changes and temperature changes are effective, and the diverging nozzle is operated under such operating conditions. It has been found that metal vapors or metal vapors and various gases can effectively alloy or chemically react by doing so. Next, what conditions are appropriate for the temperature and pressure conditions before and after rapid cooling of the gaseous mixture, that is, before and after adiabatic expansion, will be explained using the case of producing fine powder of silicon nitride as an example. Under what temperature and pressure conditions silicon nitride decomposes or remains in a combined state follows the second law of thermodynamics. That is, the combination reaction between metal silicon vapor and nitrogen gas is expressed by the following formula (1). 3(Si)+2(N ₂ )<Si ₃ N ₄ >...(1) The free energy change ΔF of this reaction (1) is expressed by the following formula:
It is expressed by (2) or formula (3). ΔF=ΔF ₀ +RTIn1/(P _Si ) ³・(P _N2 ) ² ...(2) ΔF ₀ : Standard free energy change R : Gas constant, T : Temperature [〓] P _Si : Partial pressure of metal silicon vapor P _N2 : Partial pressure of nitrogen gas ΔF=−495853−7.755TlogT+205.22T−4.575T×
(3logPsi+2logP _N2 )...(3) In equation (3), if ΔF is negative, silicon nitride as a solid is stable, and if ΔF is positive, metallic silicon vapor and nitrogen gas are stable. It is stable. Figure 2 shows the reaction state where silicon nitride is stable and the region where metallic silicon vapor and nitrogen gas are stable as gases when the nitrogen gas partial pressure (P _N2 ) is 10 ^-2 atmospheres (7.6 Torr). It is a diagram. From FIG. 2, it can be seen that under a vacuum of about 10 ^-2 atmospheres, metal silicon vapor and nitrogen gas are more stable than silicon nitride when the temperature is 2000° C. or higher. Therefore, in the method for producing fine powder of a metal compound according to the present invention, metal vapor and gas of another element are mixed in the stable region of the metal vapor, and the mixed gas is passed through a wide-spread nozzle to form a metal compound. It can be seen that it is preferable to rapidly cool the compound to a stable region and then continue cooling without causing grain growth. In addition, when the temperature and pressure in the stable region of metal vapor etc. are extremely difficult to obtain industrially, for example when the temperature exceeds 3000°C, the reaction chamber and the wide-spread nozzle, respectively. In the first reaction chamber, metal vapor is generated at an industrially practical temperature, and the metal vapor is rapidly cooled through the first wide-spread nozzle. By introducing the gas into the second reaction chamber, mixing it with the reaction gas there, and rapidly cooling it while causing a reaction through the second wide-spread nozzle, the temperature of the stable region of metal vapor is relatively low. Fine powder of metal compounds can be obtained by operating at low temperatures. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to embodiments with reference to the accompanying drawings. Example 1 FIG. 3 is a schematic diagram showing a metal compound powder manufacturing apparatus used in Example 1. In the figure, reference numeral 1 denotes a furnace shell forming a substantially hermetic container, and a crucible 2 is disposed within the furnace shell 1. The crucible 2 has a gas preheating chamber 4 having a gas introduction port 3 and a reaction chamber 5 communicating with the gas preheating chamber. A heater 6 is arranged around the crucible 2 to maintain the inside of the gas preheating chamber 4 and the reaction chamber 5 at a predetermined temperature _T1 , and the metal charged into the reaction chamber 5 is melted by this heater 6. It is made into molten metal 7 and further evaporated as metal vapor. The bottom wall 8 of the crucible 2 is provided with a conduit 10 which communicates the reaction chamber 5 with a recovery zone 9 in the furnace shell 1, and a diverging nozzle 11 is provided at the lower end of the conduit. A collision plate 13 is arranged in the recovery zone 9 to decelerate the jet stream 12 ejected from the wide-spread nozzle 11 . The recovery zone 9 is also connected to a powder collection chamber 15 via a conduit 14 . The powder collection chamber 15 is connected by a conduit 16 to a vacuum pump 18 via an on-off valve 17, and this vacuum pump reduces the pressure inside the powder collection chamber 15, and further reduces the pressure inside the collection zone 9 and reaction chamber 5, respectively. _P2
The pressure is reduced to a predetermined pressure of _P1 . Further, a powder reservoir 20 is provided in the lower part of the powder collection chamber 15 to store the metal compound powder 19 collected in the powder collection chamber, and two on-off valves 21 and 22 are operated as appropriate. By doing so, the metal compound powder 19 can be taken out to the outside without damaging the reduced pressure state in the powder collection chamber 15. Silicon nitride powder was manufactured in the following manner using the metal compound powder manufacturing apparatus thus configured. First, metal silicon is charged into the reaction chamber 5, nitrogen gas is introduced into the reaction chamber 5 from the gas introduction port 3 via the gas preheating chamber 4, and the crucible 2 housed in the furnace shell 1 is rapidly heated by the heater 6. By heating and setting the temperature T ₁ in the reaction chamber 5 to 2300°C, metal silicon is melted to form the molten silicon 7, and the pressure P ₁ in the reaction chamber 5 is set to 20 Torr by controlling the amount of nitrogen gas introduced.
(0.026 atm). Next, the mixed gas in the reaction chamber 5, that is, the mixed gas consisting of silicon vapor generated by evaporation from the molten silicon metal 7 and nitrogen gas, is heated to a pressure of P ₂ =5 to 6 Torr (0.0066 to
It was ejected through a wide-divergent nozzle 11 into a recovery zone 9 maintained at a pressure of 0.0079 atm. In this case, the mixed gas consisting of silicon vapor and nitrogen gas is rapidly cooled to a temperature T ₂ = 800°C or less by self-adiabatic expansion by the wide-spread nozzle 11, and during the rapid cooling, it becomes fine powder of silicon nitride, and excess nitrogen It moved to recovery zone 9 together with the gas. Next, the thus generated fine powder silicon nitride is decelerated by the collision plate 13 and introduced into the powder collection chamber 15 along with nitrogen gas by the vacuum pump 18, where it is collected and stored in the powder reservoir 20. Recovered. Also, from inside the powder collection chamber 15, the vacuum pump 1
8, the nitrogen gas was recovered into a nitrogen gas recovery chamber (not shown in the figure). In addition, the purity and amount of the metal silicon and nitrogen gas introduced into the metal compound powder manufacturing equipment were 99.2%, 100g, 99.99%, and 16/min, respectively.
The reaction time was 13 minutes. Characteristics of the silicon nitride powder thus produced, such as nitrogen content, average particle size, and crystal morphology, are shown in Table 1 at the end of the paper along with the results of other examples described below. Example 2 FIG. 4 is a schematic configuration diagram similar to FIG. 3 showing a metal compound powder manufacturing apparatus used in Example 3. In FIG. 4, members that are substantially the same as those shown in FIG. 3 are designated by the same reference numerals. The metal compound powder recovery apparatus used in this example has a recovery furnace 23 that is connected to the crucible 2 through a conduit 10, and a recovery zone 9 and a collision plate 13 are installed in the recovery furnace. The recovery furnace 23 is constructed in the same manner as the metal compound powder recovery apparatus shown in FIG. 3, except that the recovery furnace 23 is maintained at a predetermined temperature by a heater 24. Silicon nitride powder was manufactured in the following manner using the metal compound powder manufacturing apparatus thus configured. First, metal silicon is charged into the reaction chamber 5, nitrogen gas is introduced into the reaction chamber 5 from the gas introduction port 3 via the gas preheating chamber 4, and the crucible 2 housed in the furnace shell 1 is rapidly heated by the heater 7. By heating and setting the temperature T ₁ in the reaction chamber 5 to 2300°C, metal silicon is melted to form the molten silicon 7, and the pressure P ₁ in the reaction chamber 5 is further controlled by controlling the amount of nitrogen gas introduced.
Adjusted to 20 Torr (0.026 atm). Next, the mixed gas in the reaction chamber 5, that is, the mixed gas consisting of silicon vapor and nitrogen gas generated by evaporation from the molten silicon 7, is heated at a temperature T ₂ = 1450°C and a pressure P ₂ = 6 to 8 Torr (0.0079 to 0.0105 It was ejected through a diverging nozzle 11 into a collection zone 9 maintained at a pressure (atmospheric pressure). In this case, the mixed gas consisting of silicon vapor and nitrogen gas is rapidly cooled to a temperature T ₂ = approximately 1400°C by self-adiabatic cooling by the wide-spread nozzle 11, and during the rapid cooling, it becomes fine powder of silicon nitride, and excess nitrogen It moved to recovery zone 9 together with the gas. Next, the thus generated fine powder silicon nitride is decelerated by the collision plate 13, guided into the powder collection chamber 15 together with nitrogen gas by the vacuum pump 18, collected in the powder collection chamber, and stored in the powder reservoir 20. It was collected in The properties of the silicon nitride powder thus produced are shown in Table 1 at the end of this paper. Note that the purity and amount of the metal silicon and nitrogen gas introduced into the metal compound powder manufacturing apparatus, and the reaction time are as described in Example 1 above.
It was the same as in the case of . Example 3 The metal compound powder recovery apparatus shown in FIG. 4 was used, except that the temperature T ₂ and pressure P ₂ in the recovery furnace 23 were set to 1100°C and 4 to 5 Torr (0.0053 to 0.0066 atmospheres), respectively. A metal compound powder was produced in the same manner as in Example 2 above. The temperature of the mixed gas of silicon nitride and nitrogen gas at the outlet of the wide-ended nozzle 11 was 1000 to 1050°C. The properties of the silicon nitride powder produced in this example are shown in Table 1 at the end of this publication. In this example as well, the purity and amount of the metal silicon and nitrogen gas introduced into the metal compound powder manufacturing apparatus, and the reaction time were the same as in Example 1 described above. Example 4 FIG. 5 is a schematic diagram similar to FIGS. 3 and 4, showing a metal compound powder manufacturing apparatus used in Example 4. In FIG. 5, members that are substantially the same as those shown in FIGS. 3 and 4 are designated by the same reference numerals. The metal compound powder manufacturing apparatus used in this Example 4 consists of a first crucible 2 and a second crucible 2 which are connected to each other through a conduit 10 in a furnace shell 1.
5, and the first crucible 2 has the same structure as the crucible 2 of the metal compound powder manufacturing apparatus used in Example 1. A second reaction chamber 26 is provided within the second crucible 25 and communicates with the first reaction chamber 5 of the first crucible 2 . The tip of the first diverging nozzle 11 provided at the lower end of the conduit 10 is open in the second reaction chamber 26, and the first gas introduction port 3 provided in the first crucible 2 is opened. A similar second gas introduction port 27 is provided. The bottom wall 28 of the second crucible 25 is provided with a conduit 29 that communicates and connects the second reaction chamber 26 with the recovery zone 9 in the furnace shell 1, and a second diverging nozzle is provided at the lower end of the conduit. 30 are provided.
Also, a second reaction chamber 2 is provided around the second crucible 25.
A heater 31 is provided to maintain the inside of the heater 6 at a predetermined temperature _T2 . Therefore, according to the metal compound powder manufacturing apparatus shown in FIG. 5, (1) the metal vapor formed in the first reaction chamber 5 and the gas introduced from the first gas introduction port 3; are mixed in the first reaction chamber 5 to form a mixed gas, and the mixed gas is passed through the first wide-spread nozzle 1.
The mixed gas thus rapidly cooled is brought to a predetermined temperature in the second reaction chamber 26.
After maintaining the temperature at T ₂ , the second diverging nozzle 3
(2) The first gas introduction port 3 is closed and only the metal vapor formed in the first reaction chamber 5 is quenched by the first diverging nozzle 11, thus quenching. The metal vapor thus produced is mixed with the gas introduced from the second gas introduction port 27 in the second reaction chamber 26 to form a mixed gas, and the mixed gas is passed through the second widening nozzle 30. Rapid cooling operation (3) The mixed gas of metal vapor and gas formed in the first reaction chamber 5 is rapidly cooled by the first diverging nozzle 11, and the thus rapidly cooled mixed gas and the second Operation (4) of mixing the gas introduced from the gas introduction port 27 and rapidly cooling the mixed gas by the second diverging nozzle 30; the metal vapor and gas formed in the first reaction chamber 5; is quenched by the first diverging nozzle 11, and the thus quenched mixture gas is mixed with another metal vapor formed in the second reaction chamber 26, and the mixture thus formed is Various operations such as quenching the gas by the second diverging nozzle 30 can be performed by one metal compound powder manufacturing apparatus. In the metal compound powder manufacturing apparatus shown in FIG. 5, as shown in FIG.
By disposing the gas 34 in the vicinity of the inlet portion 33 of the second reaction chamber, the gas 34 mixed in the second reaction chamber is sucked into the second diverging nozzle by the jet 35 ejected from the first diverging nozzle. It is also possible to configure Using the metal compound powder manufacturing apparatus configured as described above, aluminum nitride powder was manufactured in the following manner. First, the first gas introduction port 3 is closed, metal aluminum is charged into the first reaction chamber 5, and the inside of the first reaction chamber 5 is heated to T ₁ =
Heating to 1900℃ to form molten aluminum 7,
In addition, the inside of the first reaction chamber 5 is P ₁ = 35 to 40Torr (0.046
~0.053 atm). Next, the first reaction chamber 5
The aluminum vapor generated in the chamber is ejected through the first wide-spread nozzle 11 into the second reaction chamber 26 maintained at a temperature T ₂ =600 to 700°C and a pressure P ₂ =5 Torr (0.0066 atmospheres). The aluminum vapor thus quenched (already in a solid phase) and the nitrogen gas introduced from the second gas introduction port 27 are mixed in the second reaction chamber 26, and the aluminum vapor thus formed is mixed with nitrogen gas introduced from the second gas introduction port 27. By rapidly cooling the mixed gas through the second wide-spread nozzle 30, aluminum nitride in the form of fine powder was obtained. The purity and amount of the metal aluminum and nitrogen gas introduced into the metal compound powder manufacturing apparatus were 99.92%, 100 g, 99.99%, and 18/min, respectively, and the reaction time was 17 minutes. The properties of the aluminum nitride thus produced are shown in Table 1 below.

[Table] Although the present invention has been described above in detail with respect to specific examples relating to the production of silicon nitride powder and aluminum nitride powder, the present invention is not limited to these examples. It will be understood that the present invention is also applicable to the production of powders of various other metal compounds such as titanium carbide and titanium carbide.

[Brief explanation of drawings]

Figures 1a to 1c are illustrations showing the operating conditions of the divergent nozzle, and Figure 2 shows the nitrogen gas partial pressure.
The reaction state diagrams showing the region in which silicon nitride is stable and the region in which metallic silicon vapor and nitrogen gas are stable as gases at 10 ^-2 atmospheres, and FIGS. 3 to 5, respectively, show the microstructure of the metal compound according to the present invention. A schematic configuration diagram showing a metal compound powder manufacturing apparatus suitable for carrying out the powder manufacturing method, and FIG. 6 is an illustrative diagram showing the positional relationship of two divergent nozzles. 1... Furnace shell, 2... Crucible, 3... Gas introduction port, 4... Gas preheating chamber, 5... Reaction chamber, 6...
Heater, 7... Molten metal, 8... Bottom wall, 9... Recovery zone, 10... Conduit, 11... Wide end nozzle, 12
... Jet stream, 13 ... Collision plate, 14 ... Conduit, 15
... Powder collection chamber, 16 ... Conduit, 17 ... Shut-off valve, 18 ... Vacuum pump, 19 ... Metal compound powder, 20 ... Powder reservoir, 21, 22 ... Switch-off valve, 23 ... Recovery furnace , 24... heater, 25...
Second crucible, 26... Second reaction chamber, 27...
Second gas introduction port, 28... bottom wall, 29...
Conduit, 30... second diverging nozzle, 31... heater, 32... tip, 33... inlet, 34...
Gas, 35...jet.

Claims (1)

[Scope of Claims] 1. While rapidly cooling a gaseous mixture of at least one metal to constitute at least one metal compound and another element by adiabatically expanding it through a diverging nozzle, the metal and the other element are rapidly cooled. A method for producing fine powder of the metal compound by reaction. 2. In the method according to claim 1, the metal is silicon, the other element is nitrogen,
A method characterized in that the metal compound is silicon nitride. 3. In the method according to claim 2, the temperature of the gaseous mixture before adiabatic expansion by the diverging nozzle is substantially 2000°C or higher, and the pressure thereof is substantially 10 ^-1 atm. A method characterized by: 4. The method according to claim 3, wherein the temperature of the metal compound after adiabatic expansion by the diverging nozzle is substantially 1000 to 1500°C. 5. Rapidly cooling at least one gaseous metal that should constitute one metal compound by adiabatically expanding it through a first diverging nozzle, and further mixing with it other elements that should constitute the metal compound in a gaseous state. and a method for producing a fine powder of the metal compound by causing the metal and the other element to react while rapidly cooling the mixed gas by adiabatically expanding it through a second diverging nozzle.