JPH07133103A - Method for synthesizing c3n4 by plasma arc method - Google Patents

Abstract

PURPOSE:To easily vaporize graphite and to produce a large quantity of C3N4 in a short time by allowing graphite to vaporize and react with nitrogen by using argon/nitrogen-mixed thermal plasma. CONSTITUTION:The thermal plasma (plasma torch 4) is generated by using a cathode tip of graphite or tungsten and a water cooled copper anode 2 as electrode in the atmosphere of gaseous argon-nitrogen mixture. The graphite 3 placed on the water-cooled copper anode 2 arranged to face oppositely to the cathode tip is sublimed or melt-vaporized to allow it to react with the argon/nitrogen-mixed thermal plasma.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for synthesizing C ₃ N ₄ . More specifically, since C ₃ N _4, which is a covalent bond of carbon and nitrogen, has a very high hardness, it is used as a partial material for abrasives, abrasive grains, cutting tools, and hard protection by coating treatment. It can be applied as a film.

[0002]

2. Description of the Related Art Generally, a hypothetical covalent solid (α-C ₃ N ₄ and β-) formed between carbon and nitrogen.
C ₃ N ₄₎ is presumed to have a very high hardness. As a method of synthesizing these C ₃ N ₄ , a method of depositing C ₃ N ₄ on germanium or a silicon substrate by sputtering carbon in a nitrogen atmosphere, that is, a carbon target sputtering treatment in a nitrogen atmosphere has been conventionally synthesized and manufactured. However, in these methods, C ₃
The synthesis speed of N ₄ is slow, and it is not suitable for a practical amount of synthesis method, and there are many problems in mass productivity and other problems. For this reason,
A high-speed industrial C ₃ N ₄ synthesizing method has been a conventional problem.

[0003]

In order to solve these problems and problems, the inventors of the present invention have heated and vaporized carbon by an argon-helium mixed plasma generated by the plasma arc method that has been performed up to now, and have carbon containing fullerenes. As a result of earnest research based on the result of depositing and forming a transition metal oxide-graphite mixture with a nitrogen plasma arc to form various metal nitrides, graphite was reacted with a plasma arc containing nitrogen. Then, CN is generated in the gas phase, and this is cooled and C is deposited on the silicon substrate mounted on the wall surface of the plasma arc furnace.
It was considered possible to precipitate ₃ N ₄ . The details of the present invention will be described below.

In the C ₃ N ₄ synthesizing method of the present invention, first of all, at the same time as heating for vaporizing carbon, a plasma torch was used for generating a reaction gas, and argon and nitrogen were used as working gases. Argon here is used for stable discharge, and nitrogen reacts with carbon to generate C ₃ N ₄
To generate. Plasma jets can also generate high energy, high temperature gas streams,
It can be used in a chemical reaction, and the reaction product is attached to the inner wall of the reaction furnace or the like, or is collected by a collecting filter or the like.

The production process of C ₃ N ₄ is inferred as shown in Table 1 from the result of the emission spectroscopic analysis of the plasma arc.

[Table 1]

[0006]

EXAMPLE FIG. 1 shows a schematic view of a plasma arc furnace used for C ₃ N ₄ synthesis of the present invention. In the figure, 1 is a stainless steel reaction vessel of a plasma arc furnace, 2 is a water-cooled anode made of copper located in the reaction vessel system, 3 is a graphite rod arranged on the water-cooled anode 2, 4 is a plasma torch, and 5 is an inner wall inside the reaction vessel. Each of the silicon wafers is attached to the.

As a method for synthesizing C ₃ N ₄ , a graphite rod 3 (φ6 mm) for spectroscopic analysis was placed on a water-cooled anode 2 in a plasma reactor furnace reaction vessel 1, and the sealed reaction vessel 1 system was once evacuated to 10 ^-1. After setting to Pa, an argon-nitrogen (1: 1) mixed gas was introduced through the plasma torch 4 and the reaction vessel 1
The system was set at 1 atm. Next, a plasma arc is generated by using an argon-nitrogen (1: 1) mixed gas as a working gas in a reaction vessel 1 system at 1 atm, and the graphite rod 3 placed on the water-cooled anode 2 is bombarded to cause graphite to CN. As a result, it was evaporated and deposited on the silicon wafer 5 attached to the inner wall inside the stainless steel reaction vessel 1.

As a result of identifying the blackish brown deposits on the silicon wafer 5 and the inner wall of the reaction vessel 1 by XPS measurement, the full width at half maximum of the C1s electron spectrum was as wide as 2.8 eV, and three peaks were obtained by Gauss division. Obtained, Eb = 28
A strong peak due to the C—N bond was observed at 6.4 eV. In addition, in the spectrum based on N1s electrons, Eb
Since it has a peak at 400 eV and a full width at half maximum of 2.0 eV, it was confirmed that only those caused by the C—N bond were included.

As a result of FTIR spectrum measurement of the deposit, the peak due to -C≡N stretching vibration was recognized around V = 2100 cm ^-1 , and the existence of C--N bond was confirmed in the deposit. . Furthermore, as a result of X-ray diffraction by XRD measurement, as a result of 2θ = 57 ° (d = 1.59 to 1.61), Si (3 1
Only the diffraction line corresponding to 1) was observed, and the diffraction line based on the precipitate was not observed. This indicates whether the precipitate is amorphous or the film thickness of the precipitate is thin. Therefore, for more detailed identification, the deposits on the inner wall of the reaction vessel were collected and identified by the powder diffraction method. As a result, in addition to the diffraction line based on graphite, a diffraction peak corresponding to β-C ₃ N ₄ shown in Table 2 was observed.

[0010]

[Table 2]

Further, the emission spectrum of the plasma jet during the impact of graphite was measured through a window beside the reaction vessel, and as a result, characteristic points about the spectrum at wavelengths of 430 nm to 330 nm were obtained. First, the intensity of the C ³ Π _U- B ³ Π _g (0-0) band of the N ₂ molecule at 358 nm is extremely weak, and secondly, the 2p ² ( ¹ D) 3p′-2p ² of the N atom at 411 nm is very weak.
( ³ P) 3s line is strong, and thirdly C at 488 nm to 485 nm
N molecules of B ² Σ-X ² Σ (0-0), (1-1), (2-2), (3-
3) and 3) that the spectrum of the (4-4) band is strongly recognized. From the above results, it was confirmed that C ₃ N ₄ was produced by the reaction between graphite and the plasma arc containing nitrogen.

[0012]

By the reaction using high temperature thermal plasma (tens of thousands of degrees), graphite can be easily vaporized and a large amount of C ₃ N ₄ can be produced in a short time.

[Brief description of drawings]

FIG. 1 is a schematic view of a plasma arc furnace for reaction used in the present invention.

[Explanation of symbols]

 1 Stainless steel reactor 2 Copper water-cooled anode 3 Graphite rod 4 Plasma torch 5 Silicon wafer

Claims (1)

[Claims] 1. A thermal plasma is generated using a graphite or tungsten cathode tip and a water-cooled copper anode as electrodes in an argon-nitrogen mixed gas atmosphere, and the argon-nitrogen mixed thermal plasma opposes the cathode tip. A method for synthesizing C ₃ N ₄ by a plasma arc method, which comprises sublimating, melting, vaporizing, and reacting graphite arranged on a water-cooled copper anode arranged.