JPH03103313A - Production device of aluminum nitride powder - Google Patents

Abstract

PURPOSE:To make it possible to continuously produce AIN over relatively long period in attachment of Al suppressed in the inside face of a reaction tube by forming the inside face of the reaction tube into a face having low wettability. CONSTITUTION:A material (e.g. BN material) 6 having low wettability to melted Al is applied to the inside face of reaction tube 1 to suppress bonding of melted Al to the inside face. Then N2 gas G and Al powder P1 are introduced from an inlet 3 into the reaction tube 1 and the Al powder P1 is dropped in suspension state in the reaction tube 1 and simultaneously heated with a heating device 2 provided around the reaction tube 1 and the Al powder P1 is subjected to nitriding reaction and then led out from an outlet 4 and separated from N2 gas G by a filter 5a and the produced AlN powder is caught in a vessel 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to aluminum nitride powder (hereinafter referred to as AlN (referred to as powder) manufacturing equipment.

BACKGROUND OF THE INVENTION Among the various AlN powder manufacturing methods known in the past,
The method that is attracting the most attention is the so-called floating direct nitriding method.

A specific example of an apparatus for carrying out this method will be explained based on the schematic diagram of FIG. It is considered to be of excellent quality. This reaction tube (1)
A heating device (2) is disposed around the middle of the tube, and its operation raises the temperature inside the reaction tube (1) to the temperature required for the nitriding reaction (usually 15,500 C).

Further, the reaction tube (1) is provided with an inlet (3) for introducing A2 powder and N2 gas into the reaction tube at a position above the heating device (2). An outlet port (4) is provided at a lower position for guiding the N2 gas and the produced A, 12N powder out of the reaction tube (1). In addition, (5) is a collection device with a filter (5a).

In this device, when N2 gas (G) and 1 powder (P1) are introduced from the inlet (3), the A base powder (P1) becomes suspended in the N2 gas atmosphere and enters the reaction tube (1). is falling. In the process, Al powder and N2 gas are heated to the heating device (2).
The reaction occurs under heating from A°C, and nitridation of the powder is achieved. At the initial stage of this nitriding reaction, only the surface portions of individual particles of Al powder are nitrided, and a hard A42N film is formed thereon, thereby causing a phenomenon in which nitriding to the inside is inhibited. However, the reaction tube (1
) As the heating temperature and reaction time increase, cracks occur in the iN film due to the difference in thermal expansion between the AkN film on the particle surface and the unreacted A4 inside, and possibly due to the difference in vapor pressure. Then, a new reaction occurs in that part,
When the reaction heat is accumulated, the temperature in the vicinity of the reaction part rapidly rises, causing the collapse of the A4N film and the splashing of molten A2, causing an accelerated chain reaction and producing AAN powder. In addition, the splashing or outflow of unreacted molten Al from the inside due to cracks in the AflN film on the surface causes the particles to become hollow, resulting in easy-to-pulverize Ap.
While forming N hollow particles, the collapse of the ApN film and the secondary nitridation of the effluent A2 results in an effect substantially corresponding to comminution. The fine A, 12N powder (P2) thus generated falls further while floating in the N2 gas, is led out of the reaction tube (1) from the outlet (4), and is filtered (
5a) and is separated from N2 gas and collected in a container (5).

Problems to be Solved by the Invention However, in the case of producing AI2N powder by the floating direct nitriding method, A4 melted during the reaction process adheres to the inner surface of the reaction tube (1) and accumulates over time, leading to premature There was a problem that the inside of the reaction tube (1) became clogged over time, making it difficult to continuously produce AQN for a long period of time.

In view of these problems, the present invention aims to provide an apparatus for producing aluminum nitride powder that can suppress the adhesion of 1 to the inner surface of a reaction tube and thereby continuously produce IN over a relatively long period of time. purpose.

Means for Solving the Problems In order to achieve the above object, the present invention includes a reaction section constituted by a reaction tube and a heating device provided around the reaction tube, and in which 12 powders are heated in the reaction tube. In an apparatus for producing aluminum nitride powder, which performs a nitriding reaction of A4 powder by suspending it in a N2 gas flow, the inner surface of the reaction tube is configured to have a low wettability surface for molten AJJ. This article focuses on the characteristic aluminum nitride powder manufacturing equipment.

Function: In the above device, the inner surface of the reaction tube is configured to have a low wettability to molten Afl, so when the molten Al in the tube comes into contact with the inner surface of the tube, it is immediately repelled and separated, or remains for a while. Even if they maintain contact, they will eventually separate due to the influence of the surrounding atmosphere, and the progress of deposition of AQ on the inner surface of the reaction tube is suppressed.

Example The present invention will be explained below based on illustrated embodiments.

The aluminum nitride powder manufacturing apparatus according to this example is as follows:
Except for the reaction tube (1), it is the same as the apparatus shown in FIG. 1, so its explanation will be omitted here.
) will be mainly explained. The symbols used in the f81 diagram shall be used as they are. The apparatus shown in Figure 1 is a so-called floating type, in particular a falling type, in which Al powder is placed on N2 gas and raised in a suspended state inside a reaction tube to carry out the nitriding reaction. It goes without saying that the present invention can be applied to a so-called floating type device.

The reaction tube (1) of the present invention has an inner surface that has low wettability against molten AR.

To achieve this, it is most preferable to use BN material for the reaction tube (1). The BN material has a contact angle with molten An (a measure that expresses the lyophobicity of a solid, that is, its wettability), which is the angle between the solid-liquid interface and the gas-liquid interface at the boundary between solid, liquid, and gas. The value (measured through the liquid phase) was 1570 at 10000C, indicating low wettability for melt 1. By the way, AJ2, which has traditionally been used for reaction tubes,
203 material is 1000 at the same temperature, and the molten Afl
The wettability was considerably high. Therefore, by using BN material in the reaction tube, during the production of aluminum nitride powder, when the molten A4 in the tube comes into contact with the inner surface of the tube,
They will be immediately repelled and separated, or even if they remain in contact for a while, they will eventually separate due to the influence of the surrounding atmosphere, causing Al to adhere and accumulate on the inner surface of the reaction tube (1). This makes it suitable for the long-term production of aluminum nitride powder.

However, it is not preferable to construct the reaction tube (1) only from BN material because BN material has relatively poor high-temperature oxidation resistance. Therefore, it is desirable that the reaction tube (1) not only have an inner surface with a low-humidity surface, but also have an outer surface with a high-temperature oxidation-resistant surface. That is, for example, the inner surface of the reaction tube (1) is made of BN material, and the outer surface is made of 12203 material, which has excellent high-temperature oxidation resistance.

Specifically, as shown in Figure 2, a commercially available BN spray was used, an extension nozzle was attached to it, and BN fine powder (6) was coated on the inner surface of a tube (7) made of Afl203 sintered body. Alternatively, as shown in FIG. 3, an inwardly protruding stopper (9) is provided on the inner surface of the lower end of the tube (8) made of Aj2203 sintered body, and the tube made of BN sintered body c. It is preferable to construct the reaction tube (1) into a double tube, etc., by inserting a tube (10) in a tight state and having its lower end abutted and supported by a stopper (9).

In the above configuration, due to the low wettability of the inner surface of the reaction tube (1),
During the production of aluminum nitride powder, molten Al is passed through a reaction tube (1
) as well as being difficult to adhere to the inner surface of the heating device (2).
) is less likely to cause corrosion of the reaction tube. In addition, in the case of conventional reaction tubes made of An203 material, 0.15% each of Si02 and MgO are used as sintering aids during manufacture.
, 0.1%, which contaminates the reaction atmosphere inside the reaction tube and reduces the purity of the produced AlN powder.
The N material can be formed to have a purity of 99.99% by removing impurities such as Fe and St by purification treatment with Cl2 gas, so that the atmosphere in the reaction tube is St, Mg
It is possible to prevent the AUN powder from being contaminated by such substances, and it is also possible to avoid a decrease in the purity of the AUN powder due to such substances.

In the above embodiment, a reaction tube made of a combination of BN material and Au203 material was described, but C material may be used instead of BN material, and mullite material (45 to 60 %Au203) may be used. The contact angle of C material to melting A℃ is 8750C.
1530, and there is no fear of contaminating the atmosphere inside the reaction tube (1) with St and Mg, and it can be used as a substitute for the BN material without inferiority.

Next, we used a drop-type manufacturing apparatus as shown in Figure 1 for the case of using a reaction tube made of only A4203 material and the case of using a reaction tube of which the inner surface of the AJ2203 tube was coated with BN fine powder. The comparative experiment conducted will be explained. A reaction tube (1) with an inner diameter of 35 mm and a length of ITrL is heated using a heating device (2) consisting of a silicone tubular furnace with a length of 300 mm.
) and manufactured by the atomization method with a purity of 99.
99%, high purity AΩ powder with a particle size of 25p or less at a rate of 0.7 g/min, and 1.0 g/min of N2 gas. It is supplied into the reaction tube (1) from the top at a rate of 5 fl/min, and the furnace temperature is 15 fl/min.
The nitriding reaction was carried out at 500C for 4 hours. As a result, A
In the reaction tube made only of R203 material, clogging occurred in 3 hours and 40% of the feed A adhered to the inner surface of the reaction tube, whereas in the reaction tube coated with BN fine powder, no clogging occurred and no The amount of AQ deposited was also only 4% of the amount of AΩ supplied. In addition, when comparing the purity of AI2N powder obtained by nitriding reaction, in the reaction tube made only of 12203 material, S1 was 250 ppm,
While Mg was 40 ppm, in the reaction tube coated with BN fine powder, Si was 28 ppII and Mg was 1 ppm. The above comparative experiments have shown that according to the present invention, the amount of A[ attached to the inner surface of the reaction tube is significantly reduced;
Scales that effectively suppress duct blockage and high-purity Al
It was confirmed that N powder could be obtained.

Effects of the Invention As described above, the apparatus for producing aluminum nitride powder of the present invention has the inner surface of the reaction tube having low wettability with respect to the molten A2, so that the molten A[ When it comes into contact with the inner surface of the reaction tube, it is immediately repelled and separated, or even if it remains in contact for a while, it eventually separates due to the influence of the surrounding atmosphere. , deposition is suppressed, and AlN can be manufactured continuously over a relatively long period of time.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an example of the aluminum nitride powder manufacturing apparatus of the present invention, Fig. 2 is a longitudinal sectional view showing one embodiment of the reaction tube, and Fig. 3 is a longitudinal sectional view showing another embodiment of the reaction tube. It is a front view. (1)...Reaction tube, (2)...Heating device. that's all

Claims (1)

[Claims] It is equipped with a reaction section consisting of a reaction tube and a heating device provided around the reaction tube, and performs a nitriding reaction of the Al powder by suspending the Al powder in an N_2 gas stream within the reaction tube. An apparatus for producing aluminum nitride powder, characterized in that the inner surface of the reaction tube is configured to have a low wettability to molten Al.