JP2932300B2 - Diamond synthesis method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for synthesizing a diamond, particularly using a hydrocarbon as a starting material and subjecting the diamond to high temperature and high pressure in the absence of a flux metal such as a Group 8 metal. To a method for synthesizing

[Prior art and problems]

Diamond has a thermodynamically stable pressure
The method of synthesizing by subjecting to the temperature range includes a so-called flux method in which the metal is once dissolved in a Group 8 metal, typically a Co or Ni-based simple metal or alloy, and precipitated as diamond, and only by the action of pressure and temperature. Direct conversion methods that cause a phase transition are known. The former is more advantageous in terms of pressure / temperature conditions, sample volume, and controllability of growth, and this method is more widely used industrially. However, the diamond obtained by this method is inevitably mixed with a flux metal or its carbide, which is one of the main causes of inferior electrical or magnetic properties as compared with natural diamond. With respect to such properties of the product, the direct conversion method is more advantageous and therefore development of this method is desired.
Conventionally, in this method, non-diamond carbon is subjected to a pressure of 10 GPa or more. The required pressure is generated by a shock wave at the time of explosive explosion or by using a press. In the former case, the generated diamond grains cannot grow due to the extremely short time of being subjected to high pressure, while in the latter case, the generated pressure is significantly higher than in the flux method, so that a larger volume is required due to the pressure containment means. In addition, there is a problem that a large-scale structure is required for reinforcing the device members, so that the volume available for accommodating the sample is greatly reduced.

By the way, "The Journal of Physical Chemistr
y) ”96 (1965) pp. 3063- RHentorf's paper states that some organic compounds, including camphene, were exposed to pressures of about 150 khar (15 GPa), 2000-
It is described that a diamond is synthesized by subjecting to a temperature of 2300 ° C. It is known that the pressure scale at the time of setting the phase transition of pb to 160 kbar (16 GPa) by observation of the resistance change is slightly inaccurate, but even if converted to the most trusted scale today, the pressure scale of 12 GPa or more is known. It is understood that it is necessary.

[Object, gist and structure of the invention]

An object of the present invention is to provide a solution to such a problem in the conventional direct conversion method. The gist of the present invention is to provide a hydrocarbon-based material, particularly a carbon compound having a cyclic molecular structure. Further, there is provided a diamond synthesizing method characterized in that it is placed in a refractory metal container in the absence of a Group 8 metal and subjected to a pressure and temperature of at least 6 GPa and 700 ° C. or more.

In the present invention, the carbonaceous material as a starting material is preferably a hydrocarbon which is solid at normal temperature, particularly a condensed polycyclic hydrocarbon, a cyclic terpene hydrocarbon, and a bridged cyclic hydrocarbon, in terms of operability, Specific examples include camphene, adamantane (both C ₁₀ H ₁₆ ) and fluorene (C ₁₃ H ₁₀ ).

This starting material is a refractory metal, typically Ta, Mo, Ti,
Alternatively, they are sealed in a Zr container, buried in a pressure medium such as pyrophyllite or pyroxene, and loaded into various hydraulic or link type high pressure devices. The conversion to diamond is completed by subjecting to a pressure of at least 5 GPa, more preferably 6-10 GPa, at a temperature of 1300 ° C. or less for several minutes. Under such temperature and pressure conditions, the synthesis equipment currently used for industrial production of diamond can be used as it is or with some improvement.

Since the obtained diamond does not contain any metal that promotes the graphitization of diamond under the heat generated during the tool making process or the heat generated during cutting and grinding, the same heat resistance as natural diamond is obtained. . Further, since no metal is contained, nodules do not occur in the process of producing the electrodeposited diamond tool.

As described above, in addition to having characteristics similar to those of natural diamond, it is possible to control the particle size and shape by selecting synthesis conditions, so that the use of synthetic diamond is expected to expand.

 Next, the present invention will be described with reference to examples and drawings.

〔Example〕

1. In the configuration schematically shown in Fig. 1,
Sample 1 consisting of mg (99% purity) was prepared with an outer diameter of 2.5 mm and a height of 4 mm.
Was sealed in a Ta container 2 and sealed with a Ta plate lid 3 and embedded in a pyrophyllite pressure medium 4. The whole was charged into an octahedral anvil-type high-pressure apparatus, and while applying a pressure of 8 GPa, it was heated to 1290 ° C. by energization through metal electrodes 5 and 6, and this condition was maintained for 30 minutes. The temperature was measured by a thermocouple 7 placed in contact with the lid 3.

The product was taken out by reducing the pressure and temperature. Microscopic observation revealed a collection of microcrystals each having a side length of 100 μm as shown in FIG. 2, and these were identified as cubic diamonds from the X-ray diffraction diagram (FIG. 3) and the Raman spectroscopic diagram.

2. The operation of the above example was repeated using fluorene 20 mg instead of camphene. However, pressure and temperature are 7GPa, 900
C was kept for 10 minutes.

X-ray diffraction measurements revealed a small amount of diamond crystals in the product.

As described above in detail, in the present invention, by using a certain kind of organic compound, direct conversion to diamond can be performed under significantly lower pressure and temperature conditions as compared with the conventional method. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the structure of a sample that can be used for carrying out the method of the present invention, FIG. 2 is a micrograph showing the shape of a diamond crystal produced in the example, and FIG. 3 is an X-ray diffraction diagram of this crystal. It is. 1 ... sample, 2 ... Ta container, 3 ... Ta plate, 4 ... pyrophyllite pressure medium, 5, 6 ... electrode, 7 ... thermocouple.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Hosomi 358-1, Yamashita, Hiratsuka-shi, Kanagawa Prefecture (72) Inventor Isao Yoshida 1-1-12-tsutsumi, Tsutsumi, Chigasaki-shi, Kanagawa Examiner Misako Anzai (58) Survey Field (Int.Cl. ⁶ , DB name) B01J 3/06 C01B 31/06 CA (STN)

Claims (4)

(57) [Claims] 1. A hydrocarbon-based material having a cyclic molecular structure is placed in a refractory metal container essentially in the absence of a Group 8 metal, and is subjected to a pressure of 6 GPa to 10 GPa and a temperature of 700 ° C. to 1300 ° C. A method for synthesizing diamond, characterized in that it is provided simultaneously. 2. The diamond synthesis method according to claim 1, wherein said hydrocarbon-based material is essentially one selected from a condensed polycyclic hydrocarbon, a cyclic terpene hydrocarbon, and a bridged cyclic hydrocarbon. . 3. The hydrocarbon-based material is essentially camphene, adamantane (both C ₁₀ H ₁₆ ) and fluorene (C ₁₃ H ₁₆ ).
Consisting of at least one party selected from _10), a diamond synthesis method according to claim 2. 4. The method of claim 1, wherein the container is essentially Ta, Ti, Zr, or Mo.
The diamond synthesis method according to claim 1, wherein the diamond synthesis method is mainly composed of a metal.