JPS5957904A - Production of ultrafine particle of metallic nitride - Google Patents

Abstract

PURPOSE:To obtain easily ultrafine particles of a metallic nitride or a mixture of said nitride and metal without forming harmful gas, by melting metal with the arc or plasma generated in N2 or gaseous mixture of N2 and inert gas and/ or H2. CONSTITUTION:When an arc 3 is generated between an electrode 2 for arc discharge in, for example, a vertical cylindrical hermetic vessel 1 and a metal 4 placed on a metal melting base 5, the metal 4 is melted. On the other hand, gaseous N2 is ejected into the vessel 1 through a gas introducing port 8 and is carried by the downward swirling gaseous flow into a cooler 7 where the gas is quickly cooled and is captured by a capturing device 9. Said molten metal 4 reacts with N2 and forms the metallic nitride of ultrafine particles. The formed metallic nitride is carried by the above-described swirling gaseous flow to the cooler 7 where the nitride is quickly cooled and captured and the ultrafine particles of the metallic nitride or the ultrafine particles mixed with the metallic nitride and the metal are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for easily producing ultrafine metal nitride particles having a diameter of 1 μm or less.

Utilizing its excellent properties, metal nitrides are widely used in ultra-hard materials, super-grade materials, catalyst materials, etc. When used as these materials, metal nitrides are made into ultra-fine particles and If you sinter it, you can make it even more powerful.

Conventionally, methods for producing ultrafine metal nitride particles include:
The main method used is to react a metal chloride or metal hydride with ammonia or nitrogen gas (hereinafter referred to as a gas phase reaction method). These gas phase reaction methods have low efficiency in converting metal hydrides or metal chlorides into metal oxides, and produce corrosive toxic gases such as hydrogen chloride and ammonia as by-products, making them difficult to operate. In addition, it has many disadvantages, such as the ultrafine metal nitride particles being contaminated, the manufacturing equipment being corroded and having poor durability, and causing pollution.

The present invention was made to eliminate these drawbacks, and its purpose is to easily produce ultrafine metal nitride particles with high purity using simple equipment, with high efficiency, and without generating harmful by-product gases. We are here to provide you with a method.

As a result of research to achieve the above object, the present inventors have discovered that nitrogen gas, a mixed gas of a nitrogen-based gas and an inert gas (He, Ar, etc.), a mixed gas of nitrogen gas and hydrogen gas, or a nitrogen gas A metal that forms nitrides (preferably a metal that generates heat through a nitriding reaction) (e.g., Ti, AI, Si, etc.) is melted by a generated arc or plasma jet in a mixed gas of an inert gas, and an aqueous gas. As a result, it was discovered that the metal nitridation reaction could be promoted and the resulting metal nitride could be obtained as ultrafine particles, and based on this knowledge, the present invention was completed.

Although the details of the formation mechanism of these ultrafine metal nitride particles are not clear, it is thought to be as follows: Ohji.

That is, at the high temperatures of the arc or plasma jet, most of the nitrogen gas dissociates into atomic or ionized states. The nitrogen atoms or ions dissociated in this way are in an activated state with significantly higher reactivity than nitrogen (molecular nitrogen) at the melting temperature of ordinary metals (approximately 3000° C. or less). Therefore, it contains this activated nitrogen.
When a metal is melted using a plasma jet or a plasma jet, a very active reaction occurs between the activated nitrogen and the molten metal. In particular, when the metal is a metal with a large affinity for nitrogen, the nitride production reaction is an exothermic reaction, and this reaction proceeds with a kind of combustion reaction. As a result, it is thought that the metal becomes ultra-fine at the same time as the nitriding of the molten metal.

The metal to be used as the metal nitride in the present invention is preferably a metal whose molten material has a large constriction and strong attraction, such as AI, Ti, 8i, Hf, Zr,
Ta, Nb, V, B, Y, U, 'I'h
, Be.

Cr, Ba, Ca, Ce, Li, Mg, M
Examples include metals or alloys of n, Mo, Pb, and Sr.

The generation rate of ultrafine metal nitride particles in the present invention increases as the nitrogen concentration of the atmosphere increases, so only nitrogen gas is preferable in this respect. However, in order to control the particle size of ultrafine particles and maintain stability of the arc or plasma jet, Ar, H
It may be diluted with an inert gas such as e.

In addition, metals with high affinity for oxygen, such as AI, T
In the case of metals such as Ca5Li, Mg, and Ba and their alloys, nitrogen or It is preferable to add hydrogen to the mixed gas of nitrogen and inert gas. In addition, the amount of hydrogen added is gold due to hydrogen! It is desirable to set the range within which the generation of A fine particles occurs, for example, usually 5 to 10 volumes, and the maximum volume to 30 volumes or less.

The atmospheric gas pressure in the present invention may be any pressure that can be stably generated by an arc or plasma jet, and the limit of this pressure is usually about 50 Torr.

As an apparatus for carrying out the present invention, a normal arc melting furnace or a plasma melting furnace can be used. However, in order to control the particle size and improve the collection efficiency of the produced ultrafine metal nitride particles, it is necessary to apply
Preferably, the No. 68 apparatus is used.

As one of the series, a device using a vertical cylindrical closed container will be described. FIG. 1 is a longitudinal sectional side view of the device, and FIG. 2 is a transverse sectional view taken along the line AA'.

Reference numeral 1 denotes a closed container, and a gas inlet 8 opening in the tangential direction is provided in the wall of the closed container 1, and a cooler 7 is provided at the bottom of the closed container 1.

Reference numeral 2 denotes an arc discharge electrode, which generates an arc 3 between the electrode 2 and the metal 4 placed on the metal melting table 5. The pot is melted and the metal reacts with nitrogen to form ultrafine metal nitride particles. The ultrafine particles of metal nitride produced are 8
The structure is such that the nitrogen gas ejected from the nitrogen gas is carried into the cooler 7 by the downward swirling airflow, is rapidly cooled, and is led to the collector 9 and collected. In other words, it is preferable to use an apparatus that quickly cools and collects the produced ultrafine metal nitride particles.

By blowing atmospheric gas around the electrode from the gas inlet 8' provided at the top of the electrode 2, protection of the electrode and transfer of generated ultrafine nitride particles to the swirling airflow become more effective. be.

According to the method of the present invention, metal nitrides with a diameter of 1 μm or less can be produced without generating harmful by-product gases.
It does not cause any pollution (in addition, highly pure metal nitride ultrafine particles can be obtained, and the manufacturing equipment and manufacturing process are simple and easy to operate.

In the following examples, 100 cm of nitrogen was used as the atmosphere, the pressure was 1 atm, the arc was an α current of 200 A, and a DC arc was used at a voltage of 20 to 30 V. However, almost the same results can be obtained by using a plasma jet instead of an arc.

Example 1 Aluminum nitride was produced using aluminum as the metal. The maximum particle size of the obtained aluminum nitride fine particles was about 0.5 μm, and the average particle size was 0.2 μm.

The particle shape is shown in the transmission electron micrograph (magnification 60) in Figure 3.
000x), it was a mixture of spherical and acicular shapes.

Example 2 The shape of titanium nitride particles using titanium as the metal is shown in the transmission electron micrograph in Figure 4 (magnification: 240,000x).
), it was a mixture of cubes and pentagonal pyramids.

Example 3 Silicon nitride fine particles were produced using silicon as the metal. The maximum particle size of the fine particles was approximately 0.8 μm, and the average particle size was 0.5 μm. The particle shape was spherical, as shown in the scanning electron micrograph of FIG. 5 (magnification: 10,000X).

Note that the ultrafine metal nitride particles obtained in each example were all of high purity.

[Brief explanation of the drawing]

FIGS. 1 and 2 show one example of an apparatus for carrying out the method of the invention.
As an example, FIG. 1 is a longitudinal sectional side view thereof, and FIG. 2 is a lateral sectional view taken along the line A-A'. Figure 3 is a transmission electron micrograph of aluminum nitride @ fine particles. Figure 4 is a transmission electron micrograph of ultrafine titanium nitride particles. Figure 5 is a scanning electron micrograph of ultrafine silicon nitride particles. 1: Airtight container 2: Radiation electrode 3: Arc 4: Metal 5: Metal melting table 7: Cooler 8: Gas inlet 8': Gas inlet 9: Collector Patent applicant Science and Technology Agency Metals Director of Materials Technology Research Institute Figure 1 Figure 2 Figure 3 Figure 17A4 Procedural amendment March 1982 λt Japanese Patent Office Commissioner Kazuo Wakasugi (Patent Office Examiner) 1. Indication of case Patent Application No. 166027 of 1982 No. 2
, Title of invention: Spontaneous correction of manufacturing method for ultrafine metal nitride particles
, - 5. Subject of amendment As shown in Column 6 of "Claims" and "Detailed Description of the Invention J" in the specification, the contents of the amendment are as shown in the appendix. "Nitrides are formed by generating an arc or plasma jet in nitrogen or a mixed gas of nitrogen, an inert gas, or hydrogen, or a mixed gas of crab, an inert gas, and hydrogen. 1. Nitride is formed by the generated arc or plasma jet. A method for producing ultrafine metal nitride particles or a mixture of metal nitride and metal, characterized by melting a metal.
(2) Insert 1 or ``Ultrafine particles mixed with metal nitride and metal'' next to ``Ultrafine particles of metal nitride'' in the eighth line under the first distance of the specification 'li. (8) On page 2, line F, line 666, insert ``or ultrafine particles of a mixture of metal nitride and metal'' next to ``metal nitride ultrafine particles''. (4) On the 7th page, line 8 from the bottom, insert K "and aluminium" after "°mu". (5) Insert "and silicon" after "silicon nitride" in the fifth line from the top of page 8. (6) Page 8, line 111 from the top, "Metal nitride" is followed by "
Alternatively, a mixture J of metal nitride and metal is inserted. (γ) Insert "and aluminum" after "aluminum nitride" in the fourth line from the bottom of page 8. (8) Insert 1 and ``silicon'' after ``electrified silicon'' in the first line from the top of page 9.

Claims (1)

[Claims] An arc or plasma jet is generated in nitrogen or a mixed gas of nitrogen and inert gas or hydrogen, or a mixed gas of nitrogen, inert gas, and hydrogen, and the generated arc or plasma jet melts the metal that forms nitride. A method for producing ultrafine metal nitride particles characterized by: