JPH06293594A - Formation of single crystal diamond particle by cvd - Google Patents

Abstract

PURPOSE:To provide a process for production of the single crystal diamond particles having excellent crystal faces and grain size range at a lower cost by providing the method for growing the single crystal onto a more inexpensive raw material particles. CONSTITUTION:A gaseous phase system consisting substantially of H2 and CH4 is excited to form the plasma and diamond and diamond-like carbon are precipitated from the gaseous phase system on seed particles of <=10mum particle size formed from a non-diamond type material having >=1100 deg.C m.p. from this plasma, by which the diamond and diamond-like carbon are grown and recovered as the single crystal of <=50mum particle size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an efficient method for producing diamond particles, particularly single crystal particles having a particle size of about 50 μm or less and particularly useful as an abrasive.

[0002]

2. Description of the Related Art With the recent development of precision industry, finer ultra-hard particles with higher precision and higher performance have been demanded.
Conventionally, diamond fine particles as such a precision polishing material have been prepared by subjecting non-diamond carbon to a catalytic metal by a static pressure method or by an impact high pressure method under conditions where a diamond of 5 GPa or more is crystallographically stable. Being manufactured.

Under pressure and temperature conditions in which diamond is metastable, diamond or diamond-like carbon (both are collectively referred to as diamond hereinafter) is synthesized by chemical vapor deposition (CVD) method by extrusion from the vapor phase. The research done is extensive. Since this method can be applied to the coating of a substrate having a relatively large area for a certain type of material, it is expected to be used as a tool material, a hard protective film, an optical material, and an electronic material. It has already been put to practical use.

Further, at this time, a technique for obtaining automorphic diamond by depositing diamond as a substrate on crushed pieces has been established.
No. 4 publication. According to this method, it is possible to grow the produced particles to have a diameter not less than twice the substrate particle diameter.
It is possible to obtain agglomerated particles having a biaxial ratio (long / short axis ratio in a particle pattern projected on a plane) of 1.3 or less.

It is also possible to produce diamond particles using the CVD method. Therefore, this technology is also being developed in consideration of its application as an abrasive.
At this time, in addition to the method of growing the spontaneously formed diamond nuclei, non-diamond crushed particles such as SiC, Si and alumina are used as the base particles for cost reduction,
A method for growing a polycrystalline diamond on this is also known (for example, JP-A-63-15609, JP-A-1).
-305808).

On the other hand, in order to exert high performance as an abrasive, it is desirable that such particles are single crystal. However, although the above publication describes the production of polycrystalline diamond particles, it does not describe a method for obtaining single crystal diamond. Also nickel,
A method for forming a single crystal film on a substrate made of cobalt or an alloy containing these as a main component is disclosed in Japanese Patent Application Laid-Open No. Hei.
No. 132687.

[0007]

As described above, the production of single-crystal diamond particles is conventionally performed by a more general high-pressure method, spontaneous nucleation, or crushed pieces of diamond particles produced by a high-pressure method. There is known a method of growing these nuclei by a CVD method using as a nucleus. In the former case, particularly in the production of fine particles of 60 μm or less, it is produced by crushing, sizing and classifying larger crystals. Therefore, in the high-pressure method, capital investment such as equipment construction is expensive, which is economically disadvantageous, and the crystallinity is not always good because of cracks and scratches on the crystal surface generated during the crushing process. I can not say that, because it is a particle that has undergone the process of crushing and classification, the particle size distribution is wide,
For this reason, its use as an abrasive grain for precision polishing has been limited. On the other hand, the latter method has a room for improvement economically because the growth rate is low in the case of spontaneous nucleation and the method of using diamond as a raw material depends on an expensive synthetic raw material. Further, it is difficult to obtain a diamond protrusion having good adhesion to metals such as Ni and Co.

The present invention provides a cheaper method for producing a single crystal diamond particle having an excellent crystal plane and particle size range (uniformity) by providing a cheaper method for growing a single crystal on a raw material particle. The purpose is to do.

[0009]

The object of the present invention is to excite a gas phase system consisting essentially of H ₂ and CH ₄ into plasma, and from this plasma, a non-diamond material having a melting point of 1100 ° C. or higher. A diamond or diamond-like carbon having a particle size of 5 μm is formed by extruding diamond or diamond-like carbon from a vapor phase system onto seed particles having a particle size of
It is a method for producing single crystal diamond-like particles, which is characterized in that it is grown and recovered as a single crystal of 0 μm or less.

As the vapor phase for depositing diamond,
According to the invention, the CH ₄ —H ₂ system is particularly preferred, H ₂
A binary system containing CH ₄ in a ratio of 1% or less with respect to the volume of is used. If necessary, a certain gas (for example, O ₂ or H ₂ O) that accelerates the precipitation reaction of diamond or contributes to the improvement of crystal quality can be used as an additive.

Seed particles in the present invention are selected from a range of metals, metal oxides, metal nitrides and metal carbides. Such metals include IVa and V of the periodic table.
a, VIa group element, particularly Ti, Zr, Hf, Ta, N
Examples thereof include b, V, W, Mo and Si, and alloys containing these as the main components. On the other hand, as carbides, oxides and nitrides, corresponding compounds of these metals, especially WC and W
₂ C, TaC, NbC, ZrC, SiC, Si ₃ N ₄ ,
MoN, c- and _{h-BN, TiO 2, SiO} 2, A
1 ₂ O ₃ may be mentioned.

According to the invention, these seed particles generally have a particle size of less than about 10 μm, in particular less than 8 μm. On overly large grains, the precipitate grows as a polycrystal rather than a single crystal. The grain size of seeds in which the precipitate begins to take a polycrystalline structure has a range and varies somewhat depending on the material, but if it is 10 μm or less specified here, it is almost a single crystal. A particle size of 8 μm or less, particularly 5 μm or less is more preferable because a complete single crystal is obtained. The particle diameter or particle size referred to here is measured by a general biaxial ratio (long / short axis ratio in a particle figure projected on a plane).

In the present invention, diamond growth is continued while the precipitate is single crystal. At this time, in general, up to a particle size of about 50 μm, a single crystal grows without any remarkable secondary growth, so that the precipitation step can be continued without any problem if the size is around this range. However, if it exceeds this, the secondary growth reaction becomes remarkable, and the purpose of the present invention is not met. Therefore, the final particle size is about 50 μm
It is suitable to be within.

In the present invention, various known techniques can be used for exciting a gas phase system. For example, microwave, hot filament method, hot plasma method and the like are examples.
These methods can be used alone or in appropriate combination.

[0015]

In the method of the present invention, single crystal diamond can be deposited on non-diamond particles by appropriately selecting the combination of the gas phase system, the material of seed particles and the particle size.

[0016]

Example 1 A vapor phase deposition apparatus as schematically shown in FIG. 1 was used. A magnetron 3 is connected to a reaction tube 1 made of quartz (for example, an inner diameter of 40 mm) via a waveguide 2. At the bottom of the reaction tube 1, a vacuum pump 4 for reducing pressure is provided.
At the top, hydrogen and methane gas are supplied from each source 5,
A pipe 8 for supplying from 6 through a mixer 7 is connected. In this example, a water cooling sleeve 9 is provided at the center of the reaction tube 1.

4 μm on a quartz disk 10 having a diameter of about 15 mm
40 mg of SiC was placed and placed near the center of the reaction tube 1. The inside of the reaction tube 1 is decompressed by the vacuum pump 4 and H ₂ is introduced to make an H ₂ atmosphere of 2.3 KPa, and the disk 10 is heated to about 900 ° C. by microwave (2.45 GHz, 220 W).
To 100 parts (volume, the same below) H ₂ and 1 in a tube
A mixed gas consisting of 1 part of CH ₄ was supplied at a rate of 100 ml / min. By appropriately discharging the gas, the pressure inside the tube was maintained at about 3.0 KPa. As a result of continuing this step for about 10 hours, clear self-shaped single crystal diamond particles having an average particle diameter of 13 μm were recovered.

[0018]

Example 2 The same operation was repeated using the same apparatus as in the above example. However, 8 μm as seed particles
Si particles of 40 mg were used. The temperature of the substrate was set to 900 ° C., and a mixed gas consisting of 100 parts of H ₂ and 0.7 part of CH ₄ was supplied into the tube at a rate of 100 ml / min. The pressure in the tube was kept at about 3.0 KPa, and this step was continued for about 10 hours to eventually collect 150 mg of free-standing clear single-crystal diamond particles having an average particle size of 13 μm.

[0019]

As described above, according to the present invention,
It is possible to economically and efficiently obtain a self-shaped diamond single crystal with sufficient strength and uniform grain size.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of an apparatus that can be used for carrying out the present invention.

[Explanation of symbols]

1 reaction tube 2 waveguide 3 magnetron 4 vacuum pump 5 hydrogen supply source 6 methane supply source 7 gas blender 8 pipe 9 cooling water sleeve 10 quartz disk for holding seeds

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[Procedure amendment]

[Submission date] March 11, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of an apparatus that can be used for carrying out the present invention.

[Explanation of symbols] 1 reaction tube 2 waveguide 3 magnetron 4 vacuum pump 5 hydrogen source 6 methane source 7 gas blender 8 pipe 9 cooling water sleeve 10 seed holding quartz disk

Claims (11)

[Claims] 1. A gas phase system consisting essentially of H ₂ and CH ₄ is excited to form plasma, and from this plasma, 1100 ° C.
To grow and recover a single crystal having a particle size of 50 μm or less by extruding diamond or diamond-like carbon from a vapor phase system on a seed particle having a particle size of 10 μm or less composed of a non-diamond substance having the above melting point. A method for producing single crystal diamond particles, characterized by: 2. The method for producing single crystal diamond particles according to claim 1, wherein the seed particles have a particle size of 8 μm or less. 3. The method for producing single crystal diamond particles according to claim 1, wherein the seed particles have a particle size of 4 μm or less. 4. The method for producing single crystal diamond particles according to claim 1, wherein the seed particles are selected from the group consisting of IVa, Va, VIa metals, Si, and alloys containing these as the main components. 5. The method for producing single crystal diamond-like particles according to claim 1, wherein the seed particles are carbides of one or more metals selected from IVa, Va, VIa group metals, and Si. 6. The method for producing single crystal diamond-like particles according to claim 1, wherein the seed particles are oxides of at least one metal selected from IVa, Va, VIa group metals, and Si. 7. The seed particles are substantially Si ₃ N ₄ , M.
a nitride selected from oN, c- or h-BN,
The method for producing a single crystal diamond particle according to claim 1. 8. The gas phase system comprises 1% by volume of H _2.
The method for producing single crystal diamond particles according to claim 1, which contains CH _{4 in the} following ratios. 9. The method for producing single crystal diamond particles according to claim 1, wherein microwave is used in the excitation of the vapor phase system. 10. The method for producing single crystal diamond particles according to claim 1, wherein a hot filament is used in the excitation of the vapor phase system. 11. The method for producing diamond particles according to claim 1, wherein hot plasma is used in the excitation of the vapor phase system.