JPH0442360B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rod-shaped diamond single crystal having an irregular cross section such as a circle or a polygon, and a method for manufacturing the same.

Diamond, which has the highest hardness of all substances, is used as the cutting edge material for bits used to excavate rocks and for dressers used to modify grinding wheels. The size of the diamond used in these tools must be approximately 1 mm or larger,
At present, since it has not been produced on an industrial scale, a natural product called botu is used.

It is known that the wear resistance of diamond varies greatly depending on the plane orientation of the crystal, and selection of the plane orientation is an important issue when used in these tools. By the way, natural diamonds are subject to melting during the production process, so they rarely have an automorphic shape, and are generally rounded, taking on various shapes depending on the melting process. Therefore, the current situation is that considerable skill is required to determine the plane orientation of the crystal and make it suitable for use as a tool.

One of the purposes of the present invention is to provide diamond with a shape suitable for these tools, and another purpose is to provide a new diamond surface condition to increase the bonding strength to the tool support. There is a particular thing.

That is, the rod-shaped diamond single crystal of the present invention has an irregular cross-sectional shape such as a circle, a polygon, or a star shape in the diamond synthesis state, and has a length that is at least 1.5 times the diameter of the equal cross-sectional area. And its length direction <111> direction or <100>
direction or <110> direction, and is characterized by its surface having frosted glass-like unevenness.

In addition, the method for producing a rod-shaped diamond single crystal of the present invention involves bringing a diamond synthesis reaction system consisting of a carbon source, a solvent metal placed in contact with the carbon source, and a seed crystal under high pressure and high temperature in which diamond is thermodynamically stable. Create an appropriate temperature gradient in the reaction chamber housing the reaction system, and heat the solvent metal so that the part of the solvent metal in contact with the carbon source is at a high temperature and the part in contact with the seed crystal is at a low temperature. In this method, carbon is transported from a high-temperature part to a low-temperature part, and carbon is precipitated and grown as diamond on a seed crystal by utilizing the difference in solubility of carbon in a solvent metal due to the temperature gradient. has the same cross-sectional shape as the target rod-shaped diamond, and its length is at least equal to the equal cross-sectional area diameter.
A diamond seed crystal that uses a solvent metal with a diameter of 1.5 times or more and is arranged in contact with the solvent metal is characterized in that the face of the diamond seed crystal is a (111) face, a (100) face, or a (110) face. .

The rod-shaped diamond single crystal according to the present invention can be synthesized by selecting the plane orientation in advance in the longitudinal direction, so there is no need to select the plane orientation as described above, and it has the advantage that a suitable plane orientation can be easily determined as a tool. have At the same time, it exhibits a ground glass-like uneven surface condition, and its large surface area increases the bonding strength when brazed or sintered on a tool support compared to natural diamond, which has a smooth surface, and during use. Another advantage is that the diamond will not fall off the tool support.

10, 11, and 12 show the rod-shaped diamond single crystal of the present invention. Each figure is a schematic explanatory diagram of a cross section having a circular, triangular, or polygonal shape, respectively, and the points indicated in the drawing schematically illustrate the frosted glass-like uneven state of the surface. 1
0 indicates a frosted glass-like uneven surface.

It is difficult to express these unevenness quantitatively, but if defined optically, it can be said that the unevenness is such that transmission is impossible due to irregular opposition.

A rod-shaped diamond single crystal having such characteristics and a method for producing the same will be described below with reference to the drawings.

FIG. 1 shows a known method for producing large diamond single crystals with euhedral shape. A diamond seed crystal 1, a solvent metal 2, and a carbon supply source 3 are stacked inside a cylindrical graphite heater 5 with a salt pressure medium 4 in between. In this case, in order to take advantage of the temperature gradient that naturally forms in the axial direction, a carbon supply source is placed in the central portion where the temperature is high, and a seed crystal is placed in the lower end portion where the temperature is low. These are placed in a pressure medium cylinder such as pyrofilite, housed in an ultra-high pressure and high temperature device, pressurized to a predetermined pressure, and then heated through a heater 5.

This creates a temperature difference between the carbon source and the seed crystal, and this causes carbon atoms to be transported from the carbon source to the seed crystal and grow as diamonds on the seed crystal. Therefore, the grown diamond 7 grows while maintaining the same surface orientation as that of the surface of the seed crystal 1 that is in contact with the solvent metal. That is, if the seed crystal has a (100) plane, the top surface of the grown diamond 7 will be a (100) plane, and if the seed crystal has a (111) plane, it will have a (111) plane.

Furthermore, if a crystal plane that is rarely seen in natural or artificial crystals, for example, a (113) plane, is artificially created by processing the seed crystal 1, the bottom surface of the grown diamond 7 will be (113). It becomes a surface.

In such a known production method, since a solvent metal having a diameter larger than the size of the normally grown diamond is used, the grown diamond can be euhedral with a smooth surface.

The present invention provides that when the diameter of the solvent metal is limited to the size of a growing diamond or less, its outer shape has the same shape as that of the solvent metal, and its outer surface exhibits a new and industrially useful surface condition. This is due to the discovery that

FIG. 2 shows a case where one cylindrical diamond single crystal is synthesized, which is one of the embodiments of the present invention. In such a case, the solvent metal 8 used is one processed into a shape with cylindrical legs. FIG. 4 is a plan view thereof. When such a sample structure is loaded into an ultra-high pressure and high temperature apparatus, pressurized to a predetermined pressure, heated and held for a certain period of time, a rod-shaped diamond shown in FIG. 10 is synthesized.

Furthermore, in order to synthesize rod-shaped diamonds having the triangular and square cross-sectional shapes shown in FIGS. 11 and 12, solvent metals having the shapes shown in the plan views of FIGS. 5 and 6 are used. Just do it. Further, FIG. 3 shows the case where a large number of rod-shaped diamonds are synthesized at one time, and the solvent metal 9 used is one of the shapes shown in FIGS. 7, 8, and 9.

In order to manufacture rod-shaped diamonds having these cross-sectional shapes, it is important to select the thickness of the solvent metal. That is, when the growth rate of diamond is fast, the diameter of the equal cross-sectional area may be relatively large, but when the growth rate is slow, the diameter of the equal cross-sectional area must be made smaller accordingly.

In such a case, if a solvent metal with an equal cross-sectional area and a large diameter is used, a diamond will grow that does not have the cross-sectional shape of the solvent metal, has a smooth surface, and has an automorphic shape, and will not be rod-shaped. There is an appropriate equal cross-sectional area diameter depending on the growth rate.

According to experiments, when the growth rate is 1 to 3 mg/H, the diameter is preferably 3 mm or less, and when the growth rate is 4 to 5 mg/H, the diameter is preferably 4 mm or less. Normally, if the growth rate exceeds 5 mg/H, the synthesized diamond will contain a large amount of solvent metal as an impurity, and the diamond will crack during bonding to a tool support or during use, making it unusable. Therefore, the growth rate is 5mg/
Since it is preferable that the diameter is 4 mm or less, the equal cross-sectional area diameter of the solvent metal used in the synthesis is preferably about 4 mm or less.

Rod-shaped diamonds synthesized in this manner are typically characterized by having a length that is at least 1.5 times the diameter of the same cross-sectional area.

Known materials are used for the solvent metal. In other words, it is Fe, Ni, Co, and alloys containing these as main components.Other alloying elements include Cr, Mn, Al, Ti,
It may contain elements such as Zr and B.

Carbon source for diamond crystal synthesis (first
3) in the figure uses pure graphite or diamond powder or a mixture thereof. The conditions for diamond synthesis are that both the seed crystal part and the carbon source are under stable pressure and temperature conditions for the diamond, and are above the eutectic point of the solvent metal and carbon used. Good crystals can be obtained by keeping the temperature difference between the carbon source and the carbon source within the range of 10 to 50°C.

The present invention will be specifically described below with reference to Examples.

Example 1 The sample configuration shown in FIG. 2 was used. As seed crystal 1, a 30/40 mesh size obtained by artificial synthesis was used. The (100) plane was chosen as the plane in contact with the solvent metal. 58Fe− as solvent metal 8
Using 42Ni alloy, it was machined into a shape with circular legs as shown in Figure 4. Its diameter was 2 mm, the leg length was 4 mm, and the dimensions of the upper disk were 7 mm in diameter and 1 mm in thickness. On top of this, 160 mg of graphite powder for spectroscopic analysis and 240 mg of artificially synthesized diamond powder with a particle size of 325/400 mesh were mixed and pressed into a disk shape with a diameter of 7 mm and a thickness of 4 mm, which was used as carbon source 3.

These were placed in a pressure medium 4 made of salt, and a sample structure was prepared using a cylindrical heater 5 made of black smoke and a pressure medium 6 made of pyrofluorite. These sample structures were pressurized to a pressure at which the diamond was stable using an ultra-high pressure and high temperature device, a pressure of 54 Kb was applied, and then heated by conduction to the heater 5 for 20 minutes at a temperature of 1420°C.
Holds time. When the temperature and pressure were released in that order and the sample was collected, a cylindrical diamond with a diameter of 2 mm and a length of about 3.5 mm was synthesized. The weight was about 30 mg, and the outer peripheral surface was an opaque crystal with frosted glass-like unevenness. The crystal orientation was identified by X-ray diffraction, and it was found that the lower surface of the cylinder was the same as the seed crystal (100) plane.

Example 2 An alloy of Fe-5Al was used as the solvent metal, and the shape was an equilateral triangle with each side of 2 mm as shown in FIG. The (111) plane was selected as the plane of the seed crystal. pressure,
The temperature conditions were 56Kb and 1480℃, which were maintained for 15 hours.
Other conditions were the same as in Example 1.

The obtained diamond was a rod-shaped diamond having a triangular cross section as shown in FIG. 11, and its length was about 3 mm. Its weight is about 15mg,
Its outer surface was uneven and opaque. When the plane orientation of the synthesized crystal was examined by X-ray diffraction, the base of the triangle was found to be a (111) plane.

Example 3 The sample configuration shown in FIG. 3 was used. Using pure Ni as the solvent metal 9, four square legs with a side of 2 mm and a length of 5.5 mm were made and stacked with a disk with a diameter of 7 mm and a thickness of 1 mm, as shown in Figure 9. The layout was such that the 1 seed crystal on the underside of each foot
One 30/40 mesh size diamond was placed on each. In two cases, the (100) plane and in the other two cases, the (111) plane was used as the seed crystal plane. Pressure and temperature conditions are
56Kb, kept at 1400℃ for 25 hours. Other conditions were the same as in Example 1. There are four rod-shaped diamonds with a square cross section as shown in Figure 12.
I got the book. Two of the four were approximately 5 mm long, and the other two were approximately 3.5 mm. The weight of each was approximately 70 mg and approximately 50 mg. When the crystal orientation of the longer one was identified, the bottom plane was the (100) plane, and the bottom plane of the shorter one was the (111) plane.

Example 4 As seed crystal 1, a 20/25 mesh size obtained by artificial synthesis was used. This crystal was polished using a diamond grinder to create (113) planes. This crystal plane was arranged so as to be in contact with the lower surface of the solvent metal 8.

Other conditions were the same as in Example 124
When the sample was collected after holding for a period of time, the diameter was approximately 2.
A round rod-shaped diamond as shown in FIG. 10 with a length of about 3.8 mm was obtained. The crystal orientation was identified by X-ray diffraction, and the bottom of the cylinder was the same as the seed crystal (100).
It was hot on the face.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing a conventional sample configuration used to synthesize a large diamond single crystal with euhedral shape, and Figures 2 and 3 are used to synthesize the rod-shaped diamond of the present invention. These are vertical cross-sectional views showing the sample structure. Figure 2 shows the case where one diamond is obtained at a time, and Figure 3 shows the case where many diamonds are obtained at one time. Figures 4 and 5. ，
Figure 6 is a plan view for explaining the shape of the solvent metal used in Figure 2, and Figures 7, 8, and 9 are for explaining the shape of the solvent metal used in Figure 3. The plan view, FIGS. 10, 11, and 12 are explanatory diagrams schematically showing a rod-shaped diamond according to the present invention. DESCRIPTION OF SYMBOLS 1... Seed crystal diamond, 2, 8, 9... Solvent metal, 3... Carbon supply source, 4... Salt pressure medium, 5... Graphite heater, 6... Pyrofluorite pressure medium, 1
0...An uneven surface like frosted glass.

Claims (1)

[Claims] 1. In the diamond synthesis state, the cross-sectional shape is circular;
It has an unusual shape such as a polygon or star shape, and
It has a length that is at least 1.5 times the equal cross-sectional area diameter, and its length direction is the <111> direction, the <100> direction, or the <110> direction, and its surface has frosted glass-like unevenness. A rod-shaped diamond single crystal characterized by having. 2. A diamond synthesis reaction system consisting of a carbon source, a solvent metal placed in contact with the carbon source, and a seed crystal is brought to a high pressure and high temperature where diamond is thermodynamically stable, and an appropriate temperature gradient is created within the reaction chamber housing the reaction system. is heated so that the part of the solvent metal in contact with the carbon supply source is at a high temperature and the part in contact with the seed crystal is at a low temperature, and the carbon is transported from the high temperature part to the low temperature part using the solvent metal as a medium. In the method of precipitating and growing carbon as diamond on a seed crystal using the difference in solubility of carbon to solvent metal due to the temperature gradient, the cross-sectional shape of the solvent metal is the same as the cross-sectional shape of the target rod-shaped diamond. has the same shape as, and its length is at least equal to the diameter of the cross-sectional area.
A rod-shaped diamond monomer is used in which a diamond seed crystal is placed in contact with the solvent metal and the plane of the diamond seed crystal is a (111) plane, a (100) plane, or a (110) plane. Method of manufacturing crystals.