JP2728477B2 - Synthesis method of vapor phase diamond - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing diamond particles, and is particularly suitable as an abrasive for surface polishing, and is further formed by mixing with a resin, a metal, a vitrified binder and the like to form a whetstone. The present invention relates to a method for synthesizing a polycrystalline diamond suitable for use by a gas phase method.

[Conventional technology]

Diamond is known as the hardest substance and is used in abrasives. The ultra-high pressure method has been used for a long time, but a method of synthesizing it by a gas phase method has recently been proposed. In the gas phase method, film-like diamond is mostly deposited, but granular diamond is obtained depending on the production conditions.

One of the methods for obtaining granular diamond is the ultra-high pressure method.

There is a method in which fine diamond particles produced by an ultra-high pressure method are used as nuclei and a CVD diamond is deposited around the cores.

The conventional method using diamond particles as a nucleus is that the core diamond is expensive, and the core diamond particles crush large diamonds or classify the scrap diamond generated when processing diamonds. However, it is difficult to obtain a shape close to a sphere, such as a particle having a sharp edge, and it is difficult to make a diamond particle grown with this as a nucleus close to a sphere. It was difficult.

In use as abrasive grains, particularly in polishing for smoothing the surface of an object, particles close to spherical are desirable as independent grains. The crystal structure of the particles is mainly polycrystalline,
It is better that new crystal planes appear one after another while being used for polishing.

[Problems to be solved by the invention]

An object of the present invention is to provide a diamond particle having a shape which is easily compatible with a matrix material as a matrix when diamond particles are used as an element of a grindstone, has excellent grinding performance as abrasive grains, and does not require surface treatment. It is in.

[Means for solving the problem]

The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the use of a carbon material whose nucleus particles are allotrope with diamond, that is, carbon black or graphite particles, allows diamond crystal growth from the core particles without difficulty. Beginning, the resulting diamond crystal has properties that are resistant to thermal strain and stress strain, and the nucleating agent has a wide choice of forms, which allows the form of the formed diamond to be adapted to the application The inventors have found that the present invention can be performed, and have completed the present invention.

That is, the gist of the present invention is to provide a method for synthesizing diamond by a gas phase method using an oxygen-containing organic compound or an organic compound to which oxygen or water is added as a raw material, and producing diamond using carbon black or graphite particles as a nucleating agent. And a method for synthesizing a vapor-phase diamond.

 Hereinafter, the present invention will be described in detail.

Granules or powders of carbon black or graphite that form diamond on the surface play a role as a filler for diamond in the forming of a grindstone or the like.

Carbon black or graphite having a particle size of 50 mm or more can be widely used, and at the same time, these nucleating agents have a large number of active sites on the surface. It is thought that the volume decreases due to the etching by the reaction with the radical species, but the nucleation point increases. Further, the shape of the formed diamond is also affected by the shape of the nucleating agent, and it is possible to obtain a diamond having a predetermined shape, for example, confetti.

In the method of the present invention, a normal gas phase method can be applied as it is.
For example, nucleating agent particles for producing diamond may be dispersed in a free state on a substrate as in a normal gas phase method.

The diamond formed on the surface of the nucleating agent is mostly granular and mostly 0.1 to 100 μm. The size of the diamond particles can be controlled by the reaction conditions, especially the reaction time, and the particle size distribution is sharp. In addition, a particle having a shape close to that of a conventional ultrahigh-pressure hexahedral single crystal or a shape having a large number of projections can be deposited. Then, not only the pure diamond but also the diamond mixed with i-carbon can be synthesized.

On the other hand, if fine particles of carbon black or graphite are dispersed on a substrate with the remaining particle diameter selected to be submicron, a uniform diamond thin film can be deposited.

Carbon black is a few hundred square meters of spheres, many of which are linked in a chain to form granules.Graphite can also be granulated by pulverization, classification, etc. Are often present, but these attached reactive groups can be removed by heat treatment. When these carbon black or graphite particles are used as a nucleating agent, the particles preferably have a secondary particle diameter of 1 to 50 μm. If the particle size is less than 1 μm, it is lost by etching with radicals and it is difficult to work as a diamond generation nucleus, which is not preferable. On the other hand, if it exceeds 50 μm, the residual amount becomes too large. Alternatively, a treatment such as removal of carbon black is required, which is not preferable.

When these carbon black or graphite powders are placed in a diamond synthesis region, etching is caused by active species such as atomic hydrogen and methyl radicals, and solid particles or vaporized particles are reduced. On the other hand, at the same time, active points where diamond crystals can be deposited appear at the solid-gas interface, diamond deposition starts, and thereafter, etching stops as the diamond covers the nucleating agent surface, and diamond growth is thought to continue. .

 Next, the present invention will be further described with reference to Examples and Comparative Examples.

〔Example〕

A hot filament method gas phase diamond synthesis apparatus having a reaction space of about 2 liters was used. A carbon black (average particle size of about 4 μm) manufactured by Hitachi Powder Co., Ltd. was suspended in methanol by ultrasonic dispersion, and the suspension was dispersed on a 20 mm × 20 mm silicon wafer.

This suspension was dispersed and the dried silicon wafer was mounted on a substrate holder in the synthesis apparatus. While maintaining the filament temperature at 2200 ° C. and the substrate temperature at 700 ° C., hydrogen gas containing 1.5% by volume of T-butanol was introduced into the apparatus at 100 NCC / min for 2 hours.

Next, as a result of examining the substrate with an optical microscope,
It was confirmed that a large number of diamond grains having a self-shape of 10 to 15 μm were precipitated. FIG. 1 shows a scanning electron microscope (SEM) photograph of a diamond particle crystal formed on a substrate at a magnification of 1000 times. Further, as a result of analyzing these precipitates by a thin film X-ray diffraction method, a diffraction peak due to a diamond crystal was recognized.

(Comparative example)

In the same manner as in the example, a hot-filament gas-phase diamond synthesis apparatus having a reaction space of about 2 liters was used.

A steel round bar is filed with a file, and the obtained flake-like powder (10 to 100 μm) is washed with alcohol, dried and then 20 mm x 20 m
An experiment was performed under the same conditions as those of the examples by dispersing the particles on a m silicon wafer.

Then, the substrate was taken out and examined with a microscope. As a result, much graphite was present on the substrate, soot-like carbon was precipitated on the iron powder, and no diamond was confirmed.

〔The invention's effect〕

A stable and reproducible diamond can be synthesized by the inexpensive method according to the present invention.

Further, the produced diamond is suitable as a polishing grain for surface polishing as it is, and is also suitable as a grindstone by mixing and molding with a resin, vitrified, a metal binder and the like.

[Brief description of the drawings]

FIG. 1 shows a sample of 1000 diamond particles generated in the example.
The SEM photograph of the magnification is shown.

Claims (2)

(57) [Claims] 1. A method of synthesizing diamond by a hot filament method using an oxygen-containing organic compound or an organic compound to which oxygen or water is added as a raw material, wherein the diamond is formed using carbon black or graphite particles as a nucleating agent. A method for synthesizing a vapor phase diamond, characterized in that: 2. The method according to claim 1, wherein the average particle size of the carbon black or graphite particles is 1 to 50 μm.