JPH11268910A - Production of gamma-phase aluminum oxide nitride of inverse-spinel structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a γ-phase aluminum oxide nitride of an inverse-spinel structure capable of rapidly and readily synthesizing high- purity alon. SOLUTION: An AlN powder is mixed with an α-Al2 O3 powder and the resultant mixed powder is melted in an atmosphere of a high-purity nitrogen gas of 99.999 vol.% by plasma arc melting and then solidified. Thereby, alon can be produced as a ρ-phase aluminum oxide nitride of an inverse-spinel structure. An evaporated substance produced at the time of plasma arc melting can be recovered to thereby directly afford an ultrafine particulate material of the alon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum oxynitride which appears in an Al ₂ O ₃ -AlN pseudo-binary phase diagram, exists only at a high temperature of 1612 ° C. or higher, and has a wide solid solution region. Γ phase of structure (Al _{(64 + x) / 3} □
_{(8-x) / 3} O _32-x N _x , where □ is a cation vacancy) A method for producing aluminum oxynitride.

[0002]

_2. Description of the Related Art FIG. 4 shows a phase diagram of a pseudo binary system of Al ₂ O ₃ —AlN. This inverse spinel structure γ phase (Al _{(64 + x) / 3} □
_{(8-x) / 3} O _32-x N _x , where □ is a cation vacancy) Aluminum oxynitride is called alon, which has high chemical stability at high temperature and high corrosion resistance in metal refining. Polycrystalline materials have high translucency in the near-ultraviolet region to the infrared region and are chemically stable, so they are attracting attention as window materials and lamp materials for next-generation aerospace. ing.

[0003] The conventional method for producing alon is as follows.
By mixing l ₂ O ₃ and AlN powder and sintering it at a temperature of 1600 ° C. or more, Al
Alon is produced by a direct solid solution reaction between ₂ O ₃ and AlN, or is produced by a method in which Al ₂ O ₃ is nitrided according to the following chemical formula 2 while being reduced with carbon in a nitrogen atmosphere.

[0004]

Embedded image Al ₂ O ₃ (s) + AlN (s) = alon (s)

[0005]

Embedded image Al ₂ O ₃ (s) + C (s) + N ₂ (g) = al
on (s) + CO (g)

[0006]

However, these conventional methods for producing alon involve a solid-state reaction.
Since lon is synthesized, it is necessary to hold the powder at a high temperature of 1612 ° C. or higher for 1 to 6 hours. For this reason, there is a problem that the atmosphere and the powder are contaminated during the synthesis, so that it is difficult to generate pure alon.

During the synthesis, the atmosphere gas (N ₂ gas, O ₂
It is necessary to strictly control the composition of the gas) to a predetermined value, and there is a disadvantage that the manufacturing process is complicated.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for producing a gamma-phase aluminum oxynitride having an inverse spinel structure capable of rapidly and easily synthesizing high-purity alon. Aim.

[0009]

According to the present invention, there is provided a method for producing a gamma-phase aluminum oxynitride having an inverse spinel structure, comprising mixing an AlN powder and an α-Al ₂ O ₃ powder, and mixing the mixed powder with a non-oxidizing powder. It is characterized by being melted by plasma arc melting in an atmosphere and solidified to produce a gamma-phase aluminum oxynitride having an inverse spinel structure.

Another method for producing a gamma-phase aluminum oxynitride having an inverse spinel structure according to the present invention comprises the steps of:
mixing with l ₂ O ₃ powder, melting the mixed powder by plasma arc melting in a nitrogen gas atmosphere having a purity of 99.99% by volume or more, and solidifying to produce γ-phase aluminum oxynitride having an inverse spinel structure. It is characterized by.

In the method for producing a gamma-phase aluminum oxynitride having a reverse spinel structure, powder of a gamma-phase aluminum oxynitride having a reverse spinel structure which is generated during melting of a plasma arc can be recovered. Further, the non-oxidizing atmosphere preferably has an oxygen concentration of 10 ^-13 % by volume or less.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a view showing a plasma arc melting furnace used in the method of the embodiment of the present invention. A water-cooled copper plate 3 serving as an anode is disposed at the bottom of the chamber 1, and a tungsten electrode 2 serving as a cathode is fixed to the upper wall of the chamber 1 and inserted vertically into the chamber 1. Further, a microgrid 5 for recovering the evaporant is disposed in the upper part of the chamber 1. A DC power supply 8 is connected between the tungsten electrode 2 and the water-cooled copper plate 3. Further, N ₂ gas is supplied into the chamber 1 through a pipe 6, and the inside of the chamber 1 is evacuated through a pipe 7. The raw material is placed as a tablet 4 in the central recess of the water-cooled copper plate 3.

In the method of this embodiment, first, AlN powder and α-Al ₂ O ₃ powder are precisely weighed at a predetermined ratio, then dispersed in, for example, an ethanol solution, and ethanol is evaporated while stirring to obtain a homogeneous solution. Mix. After the mixed powder is dried, the mixed powder is formed into a disc-shaped tablet 4 having a diameter of 20 mm and a height of 5 mm by uniaxial pressing.

The tablet 4 is placed on the water-cooled copper plate 3 of the DC arc melting furnace shown in FIG. 1, and the inside of the chamber 1 is evacuated to 10 ^-3 Pa, for example, through the pipe 7. Next, high purity N ₂ gas of, for example, 99.999% by volume is introduced into the chamber 1 up to, for example, 67 kPa. Then, the power source 8 uses the water-cooled copper plate 3 and the tablet 4 as an anode between the tungsten electrode 2 and the water-cooled copper plate 3, for example, power: 6 to 7 kW, voltage 30 to 35, current: 200
A DC power of A is applied to generate a plasma arc between the tungsten electrode 2 and the water-cooled copper plate 3 and the tablet 4. Thereby, within a few minutes, the tablet 4 dissolves,
The melt of alon is obtained in the concave portion of the water-cooled copper plate 3. In this case, the microgrid 5 collects the evaporant present in the chamber 1. This evaporated product is also alon fine particles. Next, when the plasma is stopped, the melt of alon solidifies in the water-cooled copper plate 3, and an ingot of alon is obtained.

After that, if necessary, the ingot of alon solidified in the water-cooled copper plate 3 is mechanically pulverized and pressed again for sintering. Thereby, an alon product is obtained. In order to obtain a dense sintered body, it is necessary to pulverize the ingot of alon into a submicron order. On the other hand, alo collected by the microgrid 5
n is an evaporant, most of which is fine particles on the order of nanometers, and can be directly used for sintering without pulverization.

The atmosphere in the chamber 1 during the generation of the plasma is preferably a high-purity N ₂ gas of 99.99% by volume or more. By using this atmosphere gas as a high-purity N ₂ gas, the composition fluctuation during plasma processing is small,
High precision alon can be manufactured. However, the atmosphere gas is not limited to the high-purity N ₂ gas atmosphere,
A non-oxidizing atmosphere such as a gas can be used. The non-oxidizing atmosphere preferably has an oxygen concentration of 10 ^-13 % by volume or less.

As described above, alon having extremely excellent characteristics can be synthesized in a very short time within one minute or several minutes.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An alon according to an embodiment of the present invention will now be described.
Will be described, and the result of evaluating the product will be described. Table 1 below shows the composition of the raw material powders used, and Table 2 also shows the particle size.

[0019]

[Table 1]

[0020]

[Table 2]

The purity of the high-purity N ₂ gas used to generate the plasma is 99.999% by volume, the pressure is 67 kPa, and the output is 7 kW (35 V, 200 A). FIG. 2 shows the result of identifying the phase of the sample produced by the plasma arc melting by X-ray diffraction analysis together with the elapsed time after the occurrence of the plasma arc. In FIG. 2, the horizontal axis indicates the diffraction angle, and the vertical axis indicates the diffraction intensity.
The X-ray diffraction results of the sample sampled after seconds and 60 seconds are shown. In FIG. 2, a black circle indicates an alon diffraction peak, an open square indicates an Al ₂ O ₃ diffraction peak, and an open triangle indicates an AlN diffraction peak. As shown in FIG. 2, 9 seconds after the start of the arc, Al ₂ O ₃ and AlN were still present in addition to alon.
However, after 20 seconds, all peaks are only alon peaks. Therefore, the entire amount of alon was generated in 20 seconds after the occurrence of the plasma arc. As described above, according to the method of this embodiment, the processing time conventionally required from 1 to 6 hours has been reduced to an extremely short time of 20 seconds.

Further, the evaporated substance is recovered, and X
The result of the line diffraction analysis is shown in FIG. As shown in FIG. 3, the evaporated product also showed an X-ray peak of only alon. Therefore, by collecting the evaporated material evaporated in the chamber, alon fine particles could be directly obtained. As a result of observing the evaporate by TEM, the diameter was several tens to several tens.
The particles were spherical ultrafine particles of 0 nm. Further, the electron beam diffraction pattern of the fine particles revealed that the fine particles were a single crystal.

[0023]

As described above, according to the present invention, alon can be synthesized very quickly and alon can be easily obtained. Since the processing time is short, contamination of impurities in the manufacturing process is extremely small, and high-purity alon can be manufactured. Furthermore, according to the present invention, the so-called evaporates obtained as by-products are ultrafine particles, and can be directly used without going through a subsequent pulverization step, so that the purity can be further increased.

[Brief description of the drawings]

FIG. 1 is a view showing a plasma arc melting furnace used in a method of an embodiment of the present invention.

FIG. 2 is a view showing an X-ray diffraction result of the obtained alon melt.

FIG. 3 is a view showing an X-ray diffraction result of an evaporate of alon.

FIG. 4 is an Al ₂ O ₃ -AlN pseudo binary system phase diagram.

[Explanation of symbols]

 1: Chamber 2: Tungsten electrode 3: Water-cooled copper plate 4: Tablet 5: Micro grid 6, 7: Piping 8: DC power supply

Claims (4)

[Claims] 1. An AlN powder and an α-Al ₂ O ₃ powder are mixed, and the mixed powder is melted by plasma arc melting in a non-oxidizing atmosphere and solidified to form a γ-phase aluminum oxynitride having an inverse spinel structure. A method for producing a gamma-phase aluminum oxynitride having an inverse spinel structure, characterized in that it is produced. 2. An AlN powder and an α-Al ₂ O ₃ powder are mixed, and the mixed powder is melted by plasma arc melting in a nitrogen gas atmosphere having a purity of 99.99 vol. A method for producing gamma-phase aluminum oxynitride having an inverse spinel structure, comprising producing gamma-phase aluminum oxynitride having a structure. 3. The gamma-phase aluminum oxynitride having a reverse spinel structure according to claim 1 or 2, wherein the powder of the gamma-phase aluminum oxynitride having a reverse spinel structure, which is generated during melting of the plasma arc, is recovered. Production method. 4. The non-oxidizing atmosphere has an oxygen concentration of 10%.
^The method for producing gamma-phase aluminum oxynitride having an inverse spinel structure according to claim 1, wherein the content is not more than ^-13 % by volume.