JPH01308813A - Production of aluminum nitride powder and unit therefor - Google Patents

Abstract

PURPOSE:To obtain high-purity AlN, by preheating N2 gas when Al powder is made to react in a N2 gas stream to enable the temperature in the reaction section to be reduced to suppress generation of decomposition gas from the construction material of the reaction tube. CONSTITUTION:N2 gas from its feed section A is preheated (to 200-400 deg.C) by a preheating means 11 and fed to a powder container 2 in an Al powder feed section C. Al powder in said container 3 is then made to float on a upward current of the N2 gas fed and supplied into a reaction tube 5. The Al powder thus fed, being heated through a heater 6 during passing through the reaction section in the reaction tube 5, is converted into AlN. The AlN powder thus produced is transferred, on a N2 gas stream, to a collection vessel 8, where it is separated from the N2 gas and deposited at the bottom. According this N2 gas preheating system, the nitrification will sufficiently proceed even at ca. 1,300-1,500 deg.C.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is used as a ceramic material with excellent thermal conductivity, heat resistance, and electrical insulation in fields such as semiconductor substrates, metal melters, and other metal smelting industries. The present invention relates to a method and apparatus for continuously producing aluminum nitride powder (hereinafter referred to as AlN powder).

The conventional method for producing aluminum nitride (11!N) is A.
Although there are methods such as direct nitriding from l powder and carbon reduction method from alumina powder, direct nitriding is generally used industrially.

The direct nitriding method involves a direct contact reaction between Al powder and nitrogen (N2) gas. When the surface of the Al powder is nitrided, a hard and stable aluminum nitride film is formed on the surface in the initial stage, and - Since a shell structure is formed and the nitriding reaction inside is suppressed, it becomes necessary to further nitridize the formed AlNΩN gold film. Therefore, in order to produce AlN powder, it is necessary to repeat the nitriding reaction and pulverization, and there is a problem of a decrease in purity due to contamination during the pulverization process. In addition, as seen in Japanese Patent Publication No. 36-21164, high purity Al can be produced by mixing Al powder and AlN powder in a predetermined ratio and subjecting this mixture to a nitriding reaction.
Although a method for obtaining N powder is known and generally employed, this method has the essential problem of poor yield.

In contrast to the conventional manufacturing method mentioned above, recently, Japanese Patent Application Laid-open No. 61-
As described in Japanese Patent No. 205606, the nitriding reaction is carried out in two steps, the first and second steps. In the second step, Al powder is directly nitrided in a N2 gas stream for a short period of time, and the surface is hardened. L1 Intermediate particles with an AlN film formed thereon are created, and then in a secondary reaction, the intermediate particles are held in a N2 gas stream for a longer period of time than during the primary reaction, causing AlN arytenoid film breakage and nitriding reaction to occur inside the particles. As a step forward, attempts have been proposed to efficiently produce fine AlN powder with high purity.

However, in this previously proposed method, the reaction process is divided into two stages and carried out batchwise in small quantities, so it lacks continuous operability and has the disadvantage of poor productivity.

Therefore, the present applicant previously proposed a method and apparatus for continuously producing AlN powder in Japanese Patent Application No. 62-27935.
2.Al
We have proposed a method in which Al powder in a powder supply section is fed in a suspended state to a reaction section heated at a high temperature in a reaction tube, and reacted with N2 gas in the reaction section.

Problems to be Solved by the Invention However, in this method and apparatus, until the N2 gas flow carrying the Al powder reaches the reaction section in the reaction tube, the N2 gas has a temperature ( Since the reaction part is heated for the first time, the majority of the energy required for nitriding must be provided in the reaction part, and for this reason the temperature of the reaction part is kept at 1500 The temperature had to be maintained at a high temperature of ~1600°C. For this reason, there have been drawbacks such as generation of decomposition gas from the constituent materials of the reaction tube, and limitations in the freedom of selection of constituent materials.

A further object of the present invention is to provide a method and apparatus for producing aluminum nitride that solves these drawbacks.

Means for Solving the Problems In order to achieve the above object, the present invention attempts to preheat the N2 gas before it reaches the reaction section.

That is, the present invention relates to a method for producing aluminum nitride,
In the method for producing aluminum nitride powder, the Al powder is sent into a floating state in a N2 gas flow into a reaction section in a high temperature heated state in a reaction tube having a heating means around it, and is caused to react with the N2 gas in the reaction section. This method is characterized by preheating the N2 gas before it reaches the reaction section of the tube, or alternatively, by performing the preheating of the N2 gas before adding the Al powder to the gas stream. . Furthermore, the present invention relates to an apparatus for producing aluminum nitride, including an N2 gas supply section and N2 gas supplied from the supply section.
12 Powder supply section which suspends Afl powder by a gas flow, a reaction section is formed inside by a heating means provided around it, and a reaction tube into which Al powder riding on a N2 gas flow is sent from the Al powder supply section. The apparatus for producing aluminum nitride is characterized in that a preheating means for preheating N2 gas is provided between the N2 gas supply section and the reaction section of the reaction tube.

In Figure 1, (A) is the N2 gas supply section, (B) is the l
A powder supply section and (C) a collection section are shown.

The N2 gas supply section (A) includes an N2 gas cylinder (1) and an N2 gas supply pipe (2) for supplying N2 gas from the gas cylinder to the Al powder supply section (B).

The Al powder supply section (B) includes a powder container (3) containing the raw material Al powder and a gas supply pipe (2) that opens to the N powder container (3).
2 gas inlet (2a), an agitator (4) provided at the bottom of the container, and an Al powder inlet (not shown).
It is made to float on the N2 gas flow introduced from a) and sent toward the reaction tube (5). The agitator (4) plays an auxiliary role in preventing the agglomeration of the ρ powder in the container (3) and carrying the Al powder into the rising airflow of N2 gas, but this is not necessarily necessary. It is also possible that the Al powder is disturbed and floated depending only on the N2 gas flow.

The reaction tube (5) is made of a heat-resistant material such as an alumina tube, and a heating device (6) is disposed in a part of the layer, so that a predetermined portion of the reaction tube that is heated to a high temperature by the heating device is heated. This is the reaction section (7). Reaction tube (
5) has one end directly or indirectly connected to Al through a connecting pipe.
It is connected in communication with the powder container (3) of the powder supply section (B), and the 12 powders conveyed from the AN powder supply section along with the N2 gas flow flow through the inside thereof. Then, the reaction section (7) receives heat from the heating device (6).
It is believed that a reaction occurs between the ρ powder and the N2 gas, and nitridation of the Al powder is achieved. In addition, the heating device (6)
Although an electric resistance heating furnace is most commonly used, other heating means may also be used.

The collection unit (C) includes a collection container (8) and an Al powder outlet (9) with a filter (9a) provided on the top of the collection container (8).
), and the top plate of the collection container (8) is connected to the connecting pipe (10).
The upper end of the reaction tube (5) is connected to the upper end of the reaction tube (5).

In this invention, in addition to the above, the N2 gas is preheated. In the embodiment shown in FIG. 1, the N2 gas supply section (A) is connected to the Al powder supply section (
A preheating means (11) is provided for preheating the room temperature N2 gas introduced into B) immediately before introduction. The reason for preheating the N2 gas is to provide a portion of the energy necessary for nitriding in advance, thereby relatively lowering the required temperature of the reaction section (7). However, if the preheating temperature is too high, nitridation of Al in the solid state will begin before it reaches the reaction zone.
The nitrided layer becomes thicker, making it difficult to cause a chain nitriding reaction in the reaction zone, which will be described later, and making it impossible to obtain fine AlN powder. For this reason, it is desirable to suppress the preheating temperature to a maximum of about 500°C or less. As the preheating means (11),
A heater or, if necessary, a heat exchanger may be used.

In the apparatus shown in FIG. 1, when producing AlN powder, N2 gas from the N2 gas supply section (A) is preheated by a preheating means (11) and then supplied to the powder container (3). The Al powder in the powder container (3) is suspended on the upward current of the supplied N2 gas and sent to the reaction tube (5).

The sent Al powder is transferred to the reaction section (7) inside the reaction tube (5).
In the process of flowing through the Al powder, a reaction occurs between the Al powder and the N2 gas due to the heating from the heating device (6), and nitridation of the Al powder is achieved. At the initial stage of the nitriding reaction, only the surface of the Al powder is nitrided to form a hard AlN film, which inhibits the nitriding of the inside. As the AlN powder is further heated during the transfer process, a chain nitriding reaction occurs, resulting in complete nitriding and refinement of the AlN powder. That is, as the heating temperature and reaction time increase, A! 2. Cracks occur in the AlN film due to the difference in thermal expansion between the ApN film formed on the powder surface and the unreacted Al inside, and also probably due to the difference in vapor pressure, and a new reaction occurs at that part. When the reaction heat is accumulated, the rapid temperature rise near the reaction area causes the collapse of the AlN film and the ejection of molten Ap, causing an accelerated chain reaction and producing high-purity AlN powder. . In addition, the splashing out or outflow of unreacted molten Al from inside the powder due to cracks in the AlN coating on the surface causes the powder to become hollow, forming hollow Al particles that are easy to crush, while the collapse of the AlN coating and the outflow of Al. The secondary nitriding of produces an effect substantially equivalent to comminution. Like this
In the nitriding reaction between N2 gas and Ap, the temperature of the reaction part (7) is 130°C because the N2 gas is preheated.
The process progresses satisfactorily even at temperatures of about 0 to 1500°C.

The AlN powder that has passed through the reaction section (C) as described above is directly N
2 From the connecting pipe (lO) to the collection container (8) on the gas flow
The gas is separated from the N2 gas in the collection container (7), and deposited at the bottom of the collection container (7). The separated N2 gas is discharged from the system through the discharge port (9).

In the apparatus shown in Fig. 1, the preheating of N2 gas is performed between the N2 gas supply section (A) and the Al powder supply section (B). It is sufficient to do this until the inner reaction part (7) is reached. Therefore, as shown in FIG. 2, the reaction tube (
A preheating means (11) may be provided around 5) to perform the preheating of the N2 gas and the nitriding reaction almost continuously. However, it is preferable to preheat the Al powder before placing it in the N2 gas flow, since the overall length of the reaction tube (5) can be shortened. In FIG. 2, the same components as in FIG. 1 are given the same reference numerals.

Effects of the Invention According to this invention, since the N2 gas is preheated by the preheating device before reaching the reaction section of the reaction tube, most of the energy required for the nitriding reaction is applied only in the reaction section of the reaction tube. (Therefore, the temperature of the reaction section of the reaction tube can be lowered compared to the case without preheating.

Therefore, it is possible to reduce the generation of decomposition gas from the constituent materials of the reaction tube, and it is possible to produce higher purity Ap nitride.
Another advantageous effect is that the flexibility in selecting constituent materials can be expanded. In addition, if the N2 gas is preheated before the i-powder is placed in the gas stream, the atomization method can be performed using the manufacturing apparatus shown in Example FIG. 1, which has the effect of shortening the length of the reaction tube. High-purity aluminum powder with a purity of 99.99% and an average particle size of 7.4 μm manufactured by A was used as the raw material powder.
After charging the powder into the powder container (3) of the powder supply section (B), the N2 gas with a purity of 99.999% is supplied from the N2 gas co-supply section (A) into the container.
While supplying N2 gas at a ratio of 1Ω/a+In,
Drive the agitator (4) and put Al into the N2 gas flow.
The powder was to be transferred upward toward the reaction tube (5). Here, the reaction tube (5) has an inner diameter of 36 mm and a length of 10 mm.
A 00++ m alumina tube was used, and the flow rate of N2 gas in the reaction section (7) was set to be about 1.6 aa/see.

Under the above conditions, the N2 gas introduced into the Al powder supply section (B) by the preheating device (11) consisting of a heater installed just before the powder container (3) was heated to 200°C and 400°C.
The temperature of the reaction section (7) at which the nitriding reaction is performed and 100% nitridation is possible when heated to each temperature and when N2 gas at room temperature is introduced without providing a preheating device (11). The results were as shown in Table 1 below.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of an AfiN powder manufacturing apparatus according to the present invention, and FIG. 2 is a schematic configuration diagram showing another embodiment. (A)...N2 gas supply section, (B)...Al powder supply section, (C)...collection section, (1)...gas cylinder,
(2)...N2 gas supply pipe, (3)...powder container,
(5)...Reaction tube, (6)...Heating device, (7)...
... Reaction section, (8) ... Collection container, (11) ... Preheating means. Above] 1--↑1 Takuryoku D4 Tochi J

Claims (3)

[Claims] (1) In a method for producing aluminum nitride powder, the Al powder is sent into a floating state in a flow of N_2 gas into a reaction section in a high-temperature heated state in a reaction tube having a heating means around it, and is reacted with N_2 gas in the reaction section. . A method for producing aluminum nitride powder, characterized in that N_2 gas is preheated before reaching the reaction section of the reaction tube. (2) The method for producing aluminum nitride powder according to claim 1, wherein the N_2 gas is preheated before the Al powder is placed in the gas flow. (3) N_2 gas supply section and N supplied from the supply section
A reaction tube in which a reaction section is formed inside by an Al powder supply section that suspends Al powder with a _2 gas flow and heating means provided around it, and into which Al powder riding on an N_2 gas flow is fed from the Al powder supply section. An apparatus for producing aluminum nitride, characterized in that a preheating means for preheating the N_2 gas is provided between the N_2 gas supply section and the reaction section of the reaction tube. .