JPH01157497A - Production of granular diamond - Google Patents

Abstract

PURPOSE:To produce the title granular diamond having a large grain diameter by introducing gaseous hydrocarbons into the plasma wherein the powder of diamond, metal, or inorg. material is dispersed, suspended, and fluidized to decompose the hydrocarbons, and depositing diamond on the powder. CONSTITUTION:The powder 3 of diamond, metal (e.g., Mo), or inorg. material (e.g., alumina) is placed in a reaction chamber 5, the chamber 5 is evacuated by a vacuum device 6, and then a plasma producing gas is introduced through valves 8' and 8''. A powder fluidizing gas is introduced from a valve 8''', a power is impressed on an electromagnet 11 from a power source 12 to vibrate a diaphragm 10, and the powder 3 is dispersed, suspended, and fluidized. A power is then supplied to a work coil 13 from a high-frequency power source 2 to produce high-temp. plasma at >=1700 K, gaseous hydrocarbons or an inert gas contg. an org. compd. or a carbonaceous material or gaseous H2 are introduced from a valve 8, and diamond is deposited on the powder 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing granular diamond using high temperature plasma.

Prior Art The present applicant previously proposed that high-temperature plasma generated using direct current, low-frequency alternating current, high frequency, or microwaves is rapidly cooled in the gas phase by quenching with cold gas or refrigerant, quenching with a cooling wall, or quenching with thermal expansion. It was discovered that it is possible to synthesize powdered diamond using (Japanese Patent Application Nos. 60-295739 and 61-252391).

However, in these methods, the residence time of the generated diamond powder in the plasma is short, so a large (>1 μs +
) The production of granular diamonds was difficult. We also discovered a method for synthesizing polycrystalline diamond by fluidizing powder in a low-temperature plasma space of a mixed gas of volatile hydrocarbons and hydrogen (Japanese Patent Application No. 8258/1982). However, this method had the disadvantage that the diamond precipitation rate was very slow (3 to 7μ-8).

Purpose of the Invention The present invention aims to solve these problems,
The purpose is to provide a method for producing large-diameter granular diamonds at high speed using high-temperature plasma without requiring means such as rapid cooling.

Structure of the Invention As a result of research to achieve the above object, the present inventor has discovered that diamond powder, metal powder, or inorganic powder is dispersed and suspended in a high-temperature plasma using a diaphragm, a jet gas flow, or a combination thereof to improve the surface of the powder. When diamond is precipitated in the process, the powder temperature does not rise excessively due to high-temperature plasma, the temperature can be kept at a temperature convenient for diamond growth, and the residence time can also be increased, making it possible to produce granular diamond with a large particle size. I found out that. The present invention was completed based on this knowledge.

The gist of the present invention is to apply electric discharge to a single gas or a mixed gas selected from hydrocarbon gas, hydrogen gas, and inert gas at a gas temperature of 1,700 yen.
A method for producing powdered diamond from a gas obtained by generating high-temperature plasma at a temperature higher than A method for producing granular diamond, characterized in that diamond is precipitated on the surface of the powder by dispersion and floating flow using a plate or a jet gas flow or a combination thereof.

method, (3) method using a gas flow other than the gas used for plasma, or a combination thereof.

It is desirable that the temperature of the high-temperature plasma be 1700° C. or higher; if it is lower than this, the diamond precipitation rate will be slow. The power source used for discharging may be direct current, low frequency alternating current, high frequency, or microwave, and may be electroded or electrodeless.

As the plasma generating gas, a hydrocarbon gas, an inert gas such as argon or helium, or a hydrogen gas alone or in combination is used.

When using an inert gas or hydrogen gas, an organic compound or carbon material is mixed as a carbon source.

The organic compound may be gaseous, liquid, or solid, as long as it can be decomposed in plasma to generate carbon-containing ionic species or radical species. For example, methane,
Ethane, propane, butane.

Hydrocarbons such as ethylene and benzene, polyethylene.

Examples include polymeric substances such as polypropylene, and oxygen-containing, nitrogen-containing, halogen-containing, sulfur-containing, and phosphorus-containing organic compounds such as alcohol, acetone, amines, methyl chloride, thiophene, and triethylphosphine.

Further, when hydrogen gas or hydrocarbon is mixed into the plasma, carbon monoxide or carbon dioxide can be used as a carbon source, and graphite can be used as a solid carbon source.

The plasma gas pressure used is 10 -4 to 5 x 10" atmospheres. At low pressures, the rate of diamond precipitation is slow, and at high pressures, handling of the container is troublesome.

Powders to be dispersed and suspended include diamond powder, ceramic powder such as alumina, semiconductor powder such as silicon,
Examples include metal powders such as molybdenum and stainless steel.

An apparatus for carrying out the method of the present invention will be explained based on the drawings. Figure 1 shows a case in which high-frequency discharge is used to generate high-temperature plasma, and the base powder is dispersed and suspended by a jet gas and a vibrating diaphragm. Figure 2 shows a case in which high-temperature plasma is generated using direct current discharge and the plasma flow FIG. 6 is an embodiment diagram in the case where the base powder is dispersed and suspended using another jet gas.

In FIG. 1, 1 is a high-frequency plasma torch, 2 is a high-frequency power source, 3 is a powder serving as a base, 5 is a reaction chamber, 6 is an exhaust device, 7 is a gas supply device, 8 to 8'' are gas flow 1m section valves, Reference numeral 9 indicates a gas ejection nozzle (for dispersing and floating powder), lO indicates a diaphragm, 11 indicates an electromagnet, and 12 indicates a power source for the electromagnet. A plasma generating gas is caused to flow through 8' and 8'.

In addition, a powder fluidizing gas is caused to flow through the valve 8' and the diaphragm 10 is
After vibrating the base powder 3 to disperse and float it, power is supplied from the high frequency power source 2 to the workpiece high temperature coil 13 to generate non-plasma, and raw material gas from the valve 8 or solid or fluid from the valve 14. A raw material is supplied to deposit diamond on the powder 3 of the base.

In FIG. 2, 21 is a DC plasma torch, 22 is a DC power source, and the others are the same as in FIG.

The operating procedure is to disperse and float the base powder 3 using both the plasma gas flow and the jet gas flow from the gas jet nozzle 9, and to use a DC power supply 2 instead of the high frequency power supply in Fig. 1.
2 is used, but the rest is the same as in FIG.

Example 1 Using the apparatus shown in FIG. 1, diamond powder with a particle size of 40rI11 is placed in the reaction chamber 5, and the powder is injected with argon 30j! from the gas jet nozzle 9. /win was dispersed and floated and flowed by vibrating the diaphragm 10 with the electromagnet 11. Here, alcohol vapor 1 is released from valve 8.
．． 2 g/win and argon 44! /min mixed gas, argon from valve 8' 2 f/min, valve 8'
More argon 10 j! /sin and hydrogen 12 Il/
Using the apparatus shown in Fig. 2, alumina powder with a particle size of 150 μm was placed in the reaction chamber 5, and argon 25j! /Il
+in was blown to disperse and float the powder.

To this, argon 251 is added from valve 8. /min and hydrogen 5j! methane 1/min from valve 8'.
．． 2 diamond coated particles were obtained.

Effects of the Invention According to the method of the present invention, granular diamond with a large particle size, which is difficult to obtain with the conventional method, can be easily obtained without the need for rapid cooling or other means in the conventional method.

[Brief explanation of the drawing]

The drawing shows an embodiment of the apparatus for carrying out the method of the present invention.
The figure shows a case in which particles are dispersed and floated using high-frequency discharge by vibrating a jet gas and a diaphragm. Figure 2 shows a case in which particles are dispersed and floated by a plasma flow and another jet gas using a direct current discharge. The apparatus shown in FIG. 1: High frequency plasma torch, 2: High frequency oscillator, 3: Base powder, 5: Reaction chamber, 6: Exhaust device, 7: Gas supply device,
8~8": Valve, 9: Gas jet nozzle, 10: Vibration plate, 11: Electromagnet, 12: Power source for electromagnet, 1
3: Work coil, 14: Solid and liquid raw material introduction device, 21: DC plasma torch, 22: DC power source. -5ε Figure 1 Figure 2

Claims (1)

[Claims] A single gas or a mixture of gases selected from hydrocarbon gas, hydrogen gas, and inert gas is heated to a gas temperature of 1700℃ by electric discharge.
A method for producing powdered diamond from a gas obtained by generating high-temperature plasma of K or higher and decomposing or vaporizing an organic compound or carbon material in the plasma, in which diamond, metal, or inorganic powder is vibrated in the plasma. A method for producing granular diamond, characterized in that diamond is precipitated on the surface of the powder by dispersion and floating flow using a plate, a jet gas flow, or a combination thereof.