JP4874013B2 - Aluminum nitride manufacturing method and nitriding apparatus - Google Patents

Description

  The present invention relates to a method for producing aluminum nitride, and more particularly to a method for producing spherical aluminum nitride powder.

  Aluminum nitride, a man-made ceramic that does not exist in nature, is used in applications such as semiconductor substrates due to its excellent electrical and thermal conductivity characteristics. In recent years, aluminum nitride powder has been filled as a filler in structures such as resins. By filling the aluminum nitride powder, the effect of improving the thermal conductivity of the structure is exhibited. Due to such an increase in usage, the demand for aluminum nitride is expanding.

  However, when conventional aluminum nitride powder is used for these purposes, the filling property into a resin or the like has been a problem. Conventional aluminum nitride powder has been produced by crushing massive aluminum nitride. The aluminum nitride particles that have been pulverized by crushing have an angular shape, so that the filling property is poor, the filling amount is limited, and the filling die is worn out.

  For this reason, an aluminum nitride powder made of spherical particles, which is a highly filling aluminum nitride powder, is required.

As a method for producing aluminum nitride, there is a production method in which aluminum (powder) is directly nitrided with nitrogen gas. The direct nitridation method (2Al + N ₂ = 2AlN) in which aluminum powder is directly nitrided with nitrogen gas is a manufacturing method that has been used since Briegleb et al. Since the reaction that proceeds in this production method is an exothermic reaction, aluminum nitride can be easily synthesized by placing pure aluminum powder in a nitrogen stream.

  However, in this direct nitriding method of aluminum, when the surface of aluminum is covered with a nitride film, the supply of nitrogen into the aluminum is blocked by the nitride film. When the supply of nitrogen is interrupted, the nitriding reaction of aluminum stops. For this reason, the direct nitriding method of aluminum has a defect that 100% nitride cannot be obtained. Therefore, industrially, nitriding is performed in a state heated to about 900 to 1400 ° C.

In the direct nitridation method of aluminum, the reaction is completed by repeating nitriding and crushing or adding AlF ₃ or AlN to increase the reaction efficiency. Since the aluminum nitride lump is hard, various steps are required for crushing. As a result, the manufacturing cost increases, and the resulting AlN has a high price.

  Various attempts to nitride aluminum vapor or liquid in a nitrogen stream have been published, but they have not been put into practical use industrially. Probably because the nitriding rate is low.

  Moreover, as a manufacturing method of aluminum nitride, there is a manufacturing method disclosed in Patent Document 1. The manufacturing method described in Patent Document 1 is a method in which solid pure aluminum is directly nitrided at a low temperature of 500 to 750 ° C., and the maximum temperature rise of the workpiece is kept at 900 ° C. or less. According to this production method, aluminum nitride having a small particle size and excellent crushability can be obtained.

However, the basics of the above manufacturing method are the same as "Installing a square graphite raw material tray in an electric furnace, putting pure aluminum powder and aluminum nitride powder into this, and nitriding with nitrogen gas", and still crushing The required aluminum nitride particles are not round.
Japanese Patent Laid-Open No. 2003-21251

This invention is made | formed in view of the said actual condition, and makes it a subject to provide the manufacturing method and nitriding apparatus of the aluminum nitride powder which are comprised from a substantially spherical particle | grain and do not require crushing.

In order to solve the above-described problems, the present inventors have studied the aluminum nitride production method and the nitriding apparatus , and as a result, have come to make the present invention.

The method for producing aluminum nitride of the present invention is a method for producing aluminum nitride in which an aluminum powder is held in a nitrogen gas atmosphere having a nitrogen gas pressure of 103 to 200 KPa, and a nitriding reaction proceeds at 500 to 1000 ° C. It is characterized in that the nitriding reaction is allowed to proceed in a floating state.
Further, the nitriding apparatus of the present invention includes a heating unit for holding heated aluminum powder, a reaction unit having a reaction chamber in which aluminum powder is ejected and a nitriding reaction proceeds, and aluminum powder heated in the heating unit is placed in the reaction chamber. have a, and ejection part for ejecting the nitrogen gas pressure is maintained in a nitrogen gas atmosphere 103～200KPa, characterized in that advancing the nitriding reaction at 500 to 1000 ° C..

  In the method for producing aluminum nitride of the present invention, the nitriding reaction is completed in a state where aluminum is floating. In other words, when the nitriding reaction accompanied by a large volume expansion proceeds, it can be freely expanded. Thereby, spherical particles can be formed.

  The method for producing aluminum nitride of the present invention is a method for producing aluminum nitride in which an aluminum powder is held in a nitrogen gas atmosphere having a nitrogen gas pressure of 103 to 200 KPa, and a nitriding reaction proceeds at 500 to 1000 ° C.

  In the method for producing aluminum nitride of the present invention, the aluminum powder is maintained in an atmosphere having a predetermined nitrogen gas pressure and a heating temperature, so that the nitriding reaction of aluminum proceeds. In general, the size of the primary particle diameter of ceramics is determined by the reaction start temperature, but if there is a subsequent temperature rise due to heat of reaction, the crystal grains sinter and grow and become coarse.

  By maintaining the nitrogen gas pressure at 103 to 200 KPa, a sufficient amount of nitrogen gas for the nitriding reaction is supplied to the aluminum powder. That is, when the nitrogen gas pressure is less than 103 KPa, there is a risk that air enters from the outside and the aluminum powder is oxidized. On the other hand, when the nitrogen gas pressure exceeds 200 KPa, an increase in the reaction efficiency of the nitriding reaction is not observed, and the cost required for production increases.

  Further, when the temperature of the nitriding reaction is less than 500 ° C., it takes a long time to start the nitriding reaction, and when it exceeds 1000 ° C., the particle size of the aluminum nitride particles produced becomes excessively large.

The free energy (free energy of Gibbs) of the direct nitriding method (2Al + N ₂ = 2AlN) of aluminum powder with nitrogen gas is always negative, for example, aluminum nitride is generated by holding for a long time even at a temperature of less than 460 ° C. It seems that, however, the cost required for manufacturing increases due to the longer time. Moreover, since the reaction rate of the nitriding reaction of the aluminum powder is higher at a high temperature, the nitriding reaction is caused at a temperature of 500 ° C. or higher, which is a little higher from an industrial viewpoint. The temperature of the nitriding reaction is more preferably 550 ° C. or higher.

  More specifically, it has been experimentally confirmed that when the aluminum powder is kept in a nitrogen gas atmosphere at 520 ° C., the nitriding reaction starts after 3 to 30 hours and the reaction stops at a nitriding rate of about 92%. The reason for having a long time to start the nitriding reaction is due to the oxide film formed on the aluminum surface. In normal nitriding reaction at low temperature, the oxide film cannot be reduced with nitrogen at the beginning of the reaction, so nitrogen enters the inside of the aluminum powder over time, and after a certain time the nitriding reaction starts abruptly and ends. To do. For this reason, 100% nitriding is normally difficult in nitriding at low temperature.

In the method for producing aluminum nitride of the present invention, the nitriding reaction is allowed to proceed while the aluminum powder is in a suspended state. By proceeding the nitriding reaction with the aluminum powder floating, an aluminum nitride powder having spherical aluminum nitride particles can be produced. Specifically, the conversion from aluminum to aluminum nitride is a reaction involving a large volume expansion (16 vol%), and in the state of being restrained in the raw material tray as in the conventional case, the free volume expansion is hindered and spherical It was difficult to generate particles. However, in the production method of the present invention, the conversion from aluminum to aluminum nitride (nitriding reaction) proceeds with the aluminum powder floating. Since the aluminum powder is in a floating state, the volume expansion is not inhibited when the volume expansion is caused by nitriding. This allows free volume expansion, resulting in spherical particles. In the present invention, the fact that the nitriding reaction proceeds with the aluminum powder floating indicates that the aluminum powder is in a floating state when the nitriding reaction proceeds from the start. The floating state may be any state in which the aluminum powder particles are not constrained by the adjacent aluminum powder particles, and examples thereof include a state in which the aluminum powder particles are suspended in the air in the reaction chamber for the nitriding reaction to proceed. .

It is preferable to have a step of heating the aluminum powder to the reaction temperature of the nitriding reaction, and a step of allowing the aluminum powder to float in the reaction chamber immediately before the nitriding reaction is started to advance the nitriding reaction. The aluminum powder can be efficiently heated by heating the aluminum powder until just before the start of the nitriding reaction and then allowing the nitriding reaction to proceed in a floating state. That is, it is possible to perform heating without causing energy loss, rather than heating the floating aluminum powder to the reaction temperature.

When the reaction temperature of the nitriding reaction is higher than 600 ° C., the aluminum powder is heated to 600 ° C. in a nitrogen gas atmosphere and heated from 600 ° C. to the reaction temperature in an inert gas atmosphere. preferable. By heating and heating to 600 ° C. in a nitrogen gas atmosphere, the nitrogen powder can be occluded in the aluminum powder. Moreover, the temperature of the aluminum powder can be raised without starting the nitriding reaction by raising the temperature and heating from 600 ° C. to the reaction temperature in an inert gas atmosphere.

  By occluding nitrogen in the aluminum powder before proceeding with the nitriding reaction, nitrogen that reacts with the aluminum powder in the subsequent nitriding reaction is held in the vicinity of the aluminum powder, and even if a rapid reaction occurs in the nitriding reaction An insufficient amount of nitrogen required for the nitriding reaction can be suppressed.

  The temperature rise in the step of occluding nitrogen in the aluminum powder is preferably slow. When the rate of temperature increase is increased, the aluminum powder cannot occlude a sufficient amount of nitrogen.

  In the production method of the present invention, it is preferable to raise the temperature and heat from 600 ° C. to the reaction temperature in an inert gas atmosphere. If it exceeds 600 ° C. in a nitrogen gas atmosphere, the nitriding reaction may start. For this reason, the aluminum powder can be heated to the reaction temperature (620 to 800 ° C.) without starting the nitriding reaction by heating up to the reaction temperature in an inert gas atmosphere.

  In the production method of the present invention, the inert gas constituting the inert gas atmosphere when heated to the reaction temperature of the nitriding reaction after the nitrogen storage treatment may be any gas that does not react with aluminum, such as argon gas, neon gas, Helium gas can be raised. Argon gas is preferably used as the inert gas.

The aluminum powder is preferably released into the reaction chamber where the nitriding reaction proceeds after heating to the reaction temperature in the heating chamber. By discharging the aluminum powder into the reaction chamber, the aluminum powder floats inside the reaction chamber, and the nitriding reaction proceeds. Here, it is preferable that at least nitrogen gas serving as a nitrogen source for the nitriding reaction is present in the reaction chamber.

  The means for discharging the aluminum powder into the reaction chamber is not particularly limited as long as the discharged aluminum powder is in a floating state inside the reaction chamber. For example, a method such as a method in which pressurized nitrogen gas is used to eject the inside of the reaction chamber through a nozzle, or a method in which aluminum powder is slowly dropped from above the reaction chamber can be used.

  When the means for discharging the aluminum powder into the reaction chamber is a means for jetting into the inside of the reaction chamber through a nozzle using pressurized nitrogen gas, the gas pressure of the pressurized nitrogen gas is 0. It is preferably 2 to 0.5 MPa.

  The floating time of the aluminum powder inside the reaction chamber varies depending on the conditions such as the capacity and shape of the reaction chamber, and therefore cannot be determined in general. The particle size of the produced aluminum nitride is determined by the number of collisions between aluminum powders during the nitriding reaction and the reaction temperature of the nitriding reaction. For this reason, the floating time that contributes to the number of collisions cannot be determined unconditionally.

  The temperature inside the reaction chamber is not particularly limited, and can be a predetermined temperature between 350 and 1500 ° C. In the production method of the present invention, the particle size of the produced aluminum nitride powder can be adjusted by adjusting the temperature of the reaction chamber. As the temperature in the reaction chamber increases, an aluminum nitride powder having a larger particle size can be obtained.

  The aluminum powder used as a raw material in the production method of the present invention preferably has a purity of 99.7% or more. Examples of the aluminum powder having a purity of 99.7% or more include a powder produced from the first type aluminum ingot defined in JIS H2102-1968.

  The particle size of the aluminum powder used as a raw material in the production method of the present invention is not particularly limited. A preferable aluminum powder has an average particle diameter of 5 to 50 μm.

  Moreover, the aluminum powder used as a raw material in the manufacturing method of this invention may have an oxide film on the particle | grain surface. In the atmosphere, aluminum has a characteristic of causing a reaction with oxygen contained in the atmosphere to form a stable oxide film on the surface thereof. And the manufacturing method of this invention can manufacture the aluminum nitride powder which consists of spherical particle | grains also from the aluminum powder which has such an oxide film.

  The aluminum powder used as a raw material in the production method of the present invention may be mixed with an aluminum nitride powder. When the aluminum nitride powder is mixed, the nitriding rate of the aluminum powder may be improved. The average particle diameter and mixing ratio of the aluminum nitride powder mixed with the aluminum powder are not particularly limited.

As described above, the method for producing aluminum nitride according to the present invention is a method for producing aluminum nitride in which aluminum powder is held in a nitrogen gas atmosphere having a nitrogen gas pressure of 103 to 200 KPa and the nitriding reaction proceeds at 500 to 1000 ° C. A step of heating a mixed powder of aluminum powder and aluminum nitride powder to 400 ° C. under a vacuum atmosphere, a step of heating the mixed powder to 600 ° C. under a nitrogen gas atmosphere, and a step of 620 to 800 ° C. and a step of heating in an inert gas atmosphere to a predetermined nitriding temperature between the step of releasing the powder mixture into the reaction chamber of a nitrogen gas atmosphere by slowly dropping the reaction chamber to advance the nitriding reaction, the It is characterized by that.
(Nitriding equipment)
The nitriding apparatus of the present invention includes a heating unit for holding heated aluminum powder, a reaction unit having a reaction chamber in which aluminum powder is ejected and a nitriding reaction proceeds, and aluminum powder heated in the heating unit is ejected into the reaction chamber. a jet unit for, have a nitrogen gas pressure is maintained in a nitrogen gas atmosphere 103～200KPa, characterized in that advancing the nitriding reaction at 500 to 1000 ° C..
The ejection part preferably drops aluminum powder into the reaction chamber.
The heating unit is preferably disposed above the reaction unit.
The heating unit preferably includes a holding unit that holds the aluminum powder and a heater that heats the holding unit.
It is preferable to have an atmosphere adjusting means for adjusting the internal atmosphere of the heating unit, the reaction chamber, and the ejection unit.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, aluminum nitride was manufactured.

Example 1
As an example of the present invention, a nitriding apparatus 1 was manufactured, and aluminum nitride was manufactured by nitriding aluminum powder using the nitriding apparatus 1. The configuration of the nitriding apparatus 1 is shown in FIG.

  As shown in FIG. 1, the nitriding apparatus 1 includes a heating unit 2, a reaction unit 3, and an ejection unit 4.

  The heating unit 2 includes a sample holding unit 20 that holds aluminum powder therein and a heater 21 that heats the sample holding unit 20. Further, the heating unit 2 has an atmosphere adjusting means (not shown) that adjusts the atmosphere inside the sample holding unit 20. In the heating unit 2, the heater 21 generates heat while the aluminum powder is held in the sample holding unit 20, and heats the aluminum powder held in the sample holding unit 20.

  The reaction unit 3 includes a reaction chamber unit 30 in which aluminum powder is discharged from the heating unit 2 through the ejection unit 4 and a sample heater 31 for heating the reaction chamber unit 30. The reaction unit 3 also has an atmosphere adjusting means (not shown) that adjusts the atmosphere inside the reaction chamber 30. In the reaction unit 3, the aluminum powder heated in the heating unit 2 is discharged into the reaction chamber 30 through the ejection unit 4 and is floated in the reaction chamber 30. In this state, the nitriding reaction of the aluminum powder is performed. proceed. The heater 31 heats the reaction chamber 30 to adjust the temperature of the atmosphere when the nitriding reaction proceeds.

  The jetting unit 4 connects the sample holding unit 20 of the heating unit 2 and the reaction chamber unit 30 of the reaction unit 3, and jets the aluminum powder held in the sample holding unit 20 into the reaction chamber unit 30. The ejection part 4 has a substantially L-shaped pipe line 40 extending in the vertical direction and the horizontal direction, and a nitrogen gas introduction means having a gas outlet 410 for blowing out nitrogen gas in a horizontal direction at a bent part of the pipe line 40. 41. The jetting unit 4 jets aluminum powder falling from above the pipe line 40 into the reaction chamber 30 by nitrogen gas blown from the gas blowing port 410.

  Aluminum nitride was manufactured using the nitriding apparatus 1 having the above configuration.

  First, the sample holder 20 was filled with the raw material aluminum powder together with the aluminum nitride powder. The aluminum powder is a pure aluminum (99.7% or more) aluminum powder having an average particle diameter of 5 μm manufactured by Toyo Aluminum Co., Ltd. The aluminum nitride powder is an aluminum nitride powder manufactured by Toyo Aluminum Co., Ltd. having an average particle size of 2 μm. The sample holder 20 was filled with 100 g of mixed powder in which aluminum powder and aluminum nitride powder were sufficiently mixed at a mass ratio of 1: 1.

  After filling the sample holding unit 20 with aluminum powder, the reaction system (the sample holding unit 20, the reaction chamber 30 and the ejection unit 4) of the nitriding apparatus 1 was evacuated. Then, during vacuuming, the heater 21 was simultaneously operated to heat the sample holding unit 20. In the heating by the heater 21, the temperature was raised to 400 ° C. in 80 minutes. The heating rate at this time was 5 ° C./min.

  When the temperature of the sample holding unit 20 reached 400 ° C., evacuation was stopped and introduction of nitrogen gas into the sample holding unit 20 was started. Nitrogen gas was introduced at a flow rate of 4 L / min. In the heating under the nitrogen gas atmosphere, the temperature was raised to 600 ° C. in 60 minutes. The temperature rising rate at this time was approximately 3.5 ° C./min.

  When the temperature of the sample holder 20 reached 600 ° C., argon gas was introduced instead of nitrogen gas. Argon gas was introduced at a flow rate of 4 L / min. In the heating under the argon gas atmosphere, the temperature was raised to 660 ° C. in 20 minutes. The temperature rising rate at this time was 3 ° C./min. Then, it hold | maintained at 660 degreeC for 15 minutes.

  Here, after the evacuation of the sample holding chamber 20 was completed, nitrogen gas was introduced into the reaction chamber 30 and the ejection portion 4. The reaction chamber 30 was held at 550 ° C. or 800 ° C. by the heater 31 in a state where nitrogen gas was introduced (a state where the nitrogen gas continued to flow).

  Then, the stopper 22 provided in the connection part with the pipe line 40 of the sample holding chamber 20 is opened, and the aluminum powder filled in the sample holding chamber 20 is dropped. The dropped aluminum powder is jetted into the reaction chamber 30 by the nitrogen gas blown out from the gas blowing port 410.

  The aluminum powder injected into the reaction chamber 30 diffused into the reaction chamber 30 due to the momentum during the injection, and then slowly dropped. In this embodiment, before being injected into the reaction chamber 30, the aluminum powder is heated to the reaction temperature of the nitriding reaction, and is injected into the reaction chamber 30 to come into contact with nitrogen in the atmosphere. The nitriding reaction started. The nitriding reaction progressed and completed during the dropping of the aluminum powder. Further, in this example, since the internal volume of the reaction chamber 30 was small, the aluminum powder was sprayed in several times.

  The aluminum nitride of this example was manufactured by the above method.

(Evaluation)
The manufactured aluminum nitride powder (powder deposited in the reaction chamber 30) was analyzed.

  First, the amount of nitrogen in the produced aluminum nitride powder was measured. An aluminum nitride powder (sample 1) manufactured with the temperature of the reaction chamber 30 maintained at 550 ° C. and an aluminum nitride powder (sample 2) manufactured with the temperature of the reaction chamber 30 maintained at 800 ° C. A micrograph (SEM photograph) was taken. The SEM photograph of sample 1 is shown in FIG. 2, and the SEM photograph of sample 2 is shown in FIG. As shown in FIG. 2, it can be seen that Sample 1 is a powder composed of very fine particles. Further, as shown in FIG. 3, it can be seen that the sample 2 is composed of spherical particles although the particle diameter is as small as 1 to 2 μm. In FIGS. 2 and 3, particles aggregated in a dumpling shape can be confirmed, which is aluminum nitride powder added to the raw material aluminum powder.

  Subsequently, the amount of nitrogen in the produced aluminum nitride powder was measured. The amount of nitrogen in Sample 1 was 29.3%. This value is 86% in terms of nitriding rate. Moreover, the nitrogen content in Sample 2 was 32.2%. This value is 94% in terms of nitriding rate.

  It can be seen that the aluminum nitride powder of this example is formed of spherical particles having a sufficiently high nitriding rate.

( Reference example )
As a reference example of the present invention, a nitriding apparatus 1 was produced, and aluminum nitride was manufactured by nitriding aluminum powder using the nitriding apparatus 1. The configuration of the nitriding apparatus 1 is shown in FIG.

  As shown in FIG. 4, the nitriding apparatus 1 has a configuration in which the heating unit 2 used in Example 1 is disposed above a round experimental firing furnace 5. The nitriding apparatus 1 has a heating unit 2, an ejection unit 4, and an experimental firing furnace 5.

  The heating unit 2 has the same configuration as that of the heating unit 2 in the first embodiment.

  The ejection unit 4 connects the sample holding unit 20 of the heating unit 2 and the graphite reaction chamber 50 of the experimental firing furnace 5, and ejects the aluminum powder held in the sample holding unit 20 into the reaction chamber 50. The ejection part 4 has a pipe line 42 extending in the vertical direction.

  The experimental firing furnace 5 includes a graphite reaction chamber 50. The reaction chamber 50 can adjust the internal temperature by energizing the electrode rod 51 disposed on the outer peripheral surface, and can withstand use up to 3000 ° C.

  Aluminum nitride was manufactured using the nitriding apparatus 1 having the above configuration.

  First, the sample holder 20 was filled with the raw material aluminum powder together with the aluminum nitride powder. The aluminum powder is an aluminum powder of high purity aluminum (99.97%) having an average particle diameter of 20 μm manufactured by Toyo Aluminum Co., Ltd. The aluminum nitride powder is an aluminum nitride powder manufactured by Toyo Aluminum Co., Ltd. having an average particle size of 2 μm. The sample holder 20 was filled with 120 g of mixed powder in which aluminum powder and aluminum nitride powder were sufficiently mixed at a mass ratio of 3: 5.

  After the sample holding unit 20 was filled with aluminum powder, the reaction system of the nitriding apparatus 1 (the sample holding unit 20, the ejection unit 4, and the reaction chamber 50) was evacuated. Then, during vacuuming, the heater 21 was simultaneously operated to heat the sample holding unit 20. In the heating by the heater 21, the temperature was raised to 400 ° C. in 80 minutes. The heating rate at this time was 5 ° C./min.

  When the temperature of the sample holding unit 20 reached 400 ° C., evacuation was stopped and introduction of nitrogen gas into the sample holding unit 20 was started. Nitrogen gas was introduced at a flow rate of 4 L / min. In the heating under the nitrogen gas atmosphere, the temperature was raised to 600 ° C. in 60 minutes. The temperature rising rate at this time was approximately 3.5 ° C./min.

  When the temperature of the sample holder 20 reached 600 ° C., argon gas was introduced instead of nitrogen gas. Argon gas was introduced at a flow rate of 4 L / min. The heating in the argon gas atmosphere was performed by heating up to 730 ° C. in 40 minutes. The temperature rising rate at this time was 3 ° C./min. Then, it hold | maintained at 730 degreeC for 20 minutes.

  Here, after the evacuation of the sample holding chamber 20 was completed, nitrogen gas was introduced into the reaction chamber 50 and the ejection unit 4. In addition, the reaction chamber 50 was kept at 1200 ° C. in a state where the electrode rod 51 was energized and nitrogen gas was introduced (a state where the nitrogen gas continued to flow).

  Thereafter, the stopper 22 provided at the connection portion between the sample holding chamber 20 and the pipe line 42 is opened, and the aluminum powder filled in the sample holding chamber 20 is dropped. The dropped aluminum powder falls into the reaction chamber 50.

The aluminum powder that dropped into the reaction chamber 50 diffused into the reaction chamber 50 due to the momentum of the dropping, and then slowly dropped. In this reference example , the aluminum powder is heated to the reaction temperature of the nitriding reaction just before dropping into the reaction chamber 50, and enters the reaction chamber 50 to come into contact with nitrogen in the atmosphere. The reaction started. The nitriding reaction progressed and completed during the dropping of the aluminum powder. In this reference example , a slight increase in the internal temperature of the reaction chamber 50 was confirmed as the nitriding reaction proceeded. This increase in temperature is thought to be due to the progress of the nitriding reaction, which is an exothermic reaction.

The aluminum nitride of this reference example was manufactured by the above method.

(Evaluation)
The manufactured aluminum nitride powder (powder deposited inside the reaction chamber 50) was analyzed.

First, a micrograph (SEM photograph) of the aluminum nitride powder was taken in the same manner as in Example 1. The SEM photograph is shown in FIG. As shown in FIG. 5, it can be seen that the aluminum nitride powder of this reference example is composed of spherical particles having a particle size of 10 to 20 μm. In FIG. 5, ellipsoidal particles can be confirmed, which is aluminum nitride powder added to the raw material aluminum powder.

Subsequently, in the same manner as in Example 1, the amount of nitrogen in the produced aluminum nitride powder was measured. The amount of nitrogen in the produced aluminum nitride powder was 33.6%. This value is 98% in terms of nitriding rate. It can be seen that the aluminum nitride powder of this reference example has a sufficiently high nitriding rate.

It can be seen that the aluminum nitride powder of this reference example is formed of spherical particles having a sufficiently high nitriding rate as in the case of Example 1.

  As described above, it can be seen that in each of the examples in which the nitriding reaction was completed in a floating state in which aluminum was not restrained, an aluminum nitride powder made of spherical particles was obtained. That is, according to the manufacturing method of the present invention, an aluminum nitride powder made of spherical particles can be manufactured.

It is the figure which showed the structure of the nitriding apparatus of Example 1. FIG. 2 is a SEM photograph of the aluminum nitride powder produced in Example 1. 2 is a SEM photograph of the aluminum nitride powder produced in Example 1. It is the figure which showed the structure of the nitriding apparatus of a reference example . It is a SEM photograph of the aluminum nitride powder manufactured by the reference example .

Explanation of symbols

1: Nitriding device 2: Heating unit 20: Sample holding unit 21: Heater 22: Stopper 3: Reaction unit 30: Reaction chamber unit 31: Sample heating heater 4: Jetting unit 40: Pipe line 41: Nitrogen gas introducing means 410: Gas Outlet 5: Experimental furnace 50: Graphite reaction chamber 51: Electrode rod

Claims (9)

A method for producing aluminum nitride in which an aluminum powder is held in a nitrogen gas atmosphere having a nitrogen gas pressure of 103 to 200 KPa, and a nitriding reaction proceeds at 500 to 1000 ° C.,
A method for producing aluminum nitride, characterized in that a nitriding reaction is allowed to proceed while the aluminum powder is floating. Heating the aluminum powder to a nitriding reaction temperature;
Suspending the aluminum powder in a reaction chamber immediately before the nitriding reaction starts, and advancing the nitriding reaction;
The method for producing aluminum nitride according to claim 1, comprising: 3. The heating according to claim 2 , wherein when the reaction temperature of the nitriding reaction is higher than 600 ° C., the temperature is raised to 600 ° C. in a nitrogen gas atmosphere and heated, and from 600 ° C. to the reaction temperature is heated in an inert gas atmosphere. A method for producing aluminum nitride.   3. The method for producing aluminum nitride according to claim 2, wherein the aluminum powder is released into a reaction chamber in which a nitriding reaction proceeds after being heated to the reaction temperature in a heating chamber. A heating unit for holding heated aluminum powder;
A reaction section having a reaction chamber in which the aluminum powder is jetted and a nitriding reaction proceeds;
An ejection part for ejecting the aluminum powder heated in the heating part into the reaction chamber;
I have a,
A nitriding apparatus characterized by maintaining a nitrogen gas pressure in a nitrogen gas atmosphere having a nitrogen gas pressure of 103 to 200 KPa and causing a nitriding reaction to proceed at 500 to 1000 ° C.   The nitriding apparatus according to claim 5, wherein the jetting part drops the aluminum powder into the reaction chamber.   The nitriding apparatus according to claim 6, wherein the heating unit is disposed above the reaction unit.   The nitriding apparatus according to claim 5, wherein the heating unit includes a holding unit that holds the aluminum powder and a heater that heats the holding unit.   The nitriding apparatus according to claim 5, further comprising an atmosphere adjusting unit that adjusts an internal atmosphere of the heating unit, the reaction chamber, and the ejection unit.

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