Method used for the synthesis of the needle-shaped lengthened diamonds

FIELD: inorganic chemistry; mining industry; electronics; other industries; methods of the synthesis of the needle-shaped and lengthened diamonds.

SUBSTANCE: the invention is pertaining to the field of the inorganic chemistry, in particular, to the method of production of the needle shape synthetic diamonds and may be used in the industrial production of the special-purpose diamonds, for example, for manufacture of the boring crown bits and the dressers, and also in the capacity of the blocks details of the audio-video playback equipment, for manufacture of the feeler probes, in the micro-mechanical devices etc. The method provides for commixing of the fusion charge composed of the alloy of Mn-Ni-Fe in the mass ratio of 60±5÷30±5÷10±5 and the powder of the carbon-containing substance and treatment of the mixture at the pressure exceeding 40 kbar and the temperature over 950°С at heating rate less than 100°C/minutes. In the capacity of the carbon-containing substance use the needle-shaped coke or graphite on the coke basis with the single-component anisotropic structure with the degree of graphitization of no less than 0.55 relative units. The invention allows to simplify the production process of the synthesis of the needle-shaped and lengthened diamonds and to increase the percentage of their output within one cycle of the production process.

EFFECT: the invention ensures simplification of the production process of the synthesis of the needle-shaped and lengthened diamonds, the increased percentage of their output within one cycle of the production process.

2 ex, 2 dwg

 

The invention relates to the field of inorganic chemistry, namely the method of production of synthetic diamonds elongated and under high static pressures and temperatures with the use of carbon-graphite material and solvent-catalyst, and may find application as components nodes to be audio - or video playback, for making probes, micromechanical devices, as heatsinks for the manufacture of tools, in which diamond grains are oriented in a special way, for example, in drilling crowns and ruling pencils.

The known method of synthesis of diamonds in the shape of a needle with conductive properties (see U.S. patent No. 3310501, CL 252-502, 1957), in which the acicular diamond shape obtained by the addition of boron in the reaction cell with a special design.

In French patent No. 2243906, CL SW 31/06, 1976 elongated diamonds with ribbed hem synthesized in the reaction cell special designs, however, the synthesis process has a random character. A necessary condition for the process of synthesis occurs in graphite weak zones, which penetrates the metal-solvent, is unconditional and is not regulated. In the synthesis process get single crystals.

The method according to U.S. patent No. 4036937, CL 423-407, 1977 improves the method of synthesis according to French patent No. 2243906. In this paragraph the tent getting elongated diamond particles is also achieved by the special design of the reaction cell. This carbonaceous material is used in the form of a hollow cylinder, inside of which is placed a metal solvent. The ratio of the thickness of the walls of the cylinder to its internal diameter must be within 1:20 to 1:5. Elongated diamonds are obtained through the same effect penetration of the metal solvent through cracks in the graphite cylinder, as in French patent No. 2243906. This method has the same disadvantages as the method according to the French patent.

Waiten and Amentiferous - "Synthetic diamonds", 1973, No. 4, p.3-7 and Butuzov, Vlaev and Stunin - DAN SSSR, 1975, 20, R-720, has developed a method of growing acicular and tabular crystals by careful selection of the synthesis temperature and temperature gradient at the location of the growing crystal. Single crystals were grown on the seed in metastable conditions. A.ËCID ËMiyamoto etc. - Sat. Superhard materials: synthesis, properties, application. Sciences. Dumka. Kiev, 1983, p.45 - informed about how to obtain the acicular diamond in the reaction cell complex construction: - tube of metal foil is placed spectroscopic graphite, which is inserted into a rod of boron nitride. Prior to Assembly cells on the inner surface of the metal tube besieged by vacuum evaporation of a gold layer with a thickness of several thousand angstr the m The maximum length of an acicular crystals is 0.8 mm, the ratio of the crystal length to its width is from 2 to 20. The output of such diamonds accounted for about 10% of the total mass of crystals per cycle of synthesis. The authors argue that the addition of Au is always necessary for the formation of elongated diamonds, and the influence of the temperature gradient cannot be found. The disadvantage of this method is the complexity of technology and consumption of the precious metal Au.

The closest in technical essence and the achieved result is a method for the synthesis of needle-like and elongated diamonds, including the use of the mixture of the alloy Mn-Ni-Fe, in a weight ratio of 60±5:30±5:10±5, and graphite powder, mixing them, and processing the mixture at a pressure of >40 kbar and T>950°C, and the heating rate is adjusted so that it was <100°C/min (see paponi No. 48-42355, CL SW 31/06, 1973).

The disadvantages of this method include the difficulty of manufacturing technology and high cost due to the necessity of using a special design of the reaction cell and precious metals.

An object of the invention is to simplify the technology of synthesis of needle-like and elongated diamonds and increase their output in one cycle of the synthesis process.

The specified technical task is solved in that the synthesis of needle-like and elongated diamond is the use of the mixture of the alloy Mn-Ni-Fe, in a weight ratio of 60±5:30±5:10±5, and powder or disks carbon-containing substance, by mixing them or interlayering (in the case of disks) and processing the mixture at a pressure of >40 kbar and a temperature T>950°in the reaction cell.

Thus the heating rate of the reaction cell using the programmable controller is set such that it was less than 100°C/min

According to the invention, the carbonaceous material used needle coke or graphite-based coke with one-component anisotropic structure, with coke or graphite have graphitization degree is not less than 0.55 and relative units.

Graphite is made by the standard technology of reactor grade graphite HSV, THE 48-20-86-76 using oil pyrolysis coke (for example CNPS). Material type HSV is characterized by the following parameters: C=6,719 Åand=2,4636 Å, where C is the lattice parameter along the axis C; a - lattice parameter axis in angstroms.

The coherent scattering (crystallite size) of such graphite is characterized by the values La=455÷550 Å and Lc=180÷200 Å and the degree of graphitization is set to g=0.75÷0.80 Rel. units. Coke has a high content of striated component in the texture of the material. Use graphite coke one is the component of the anisotropic structure allows to reach the value of graphitization in the range g=0,55÷ 0,80 relative units at temperatures 2500-2800°respectively, while graphite, balanced striated and spherical components, characterized by the value of graphitization in the range g=0,36÷0,44 oted at the same temperature. Since the birth of the diamond crystal is in the solid phase due to the restructuring of the lattice microcrystallites of graphite or reconstructive martensitic mechanism at high pressures and temperatures, needle coke are the matrix-the seed for further growth of the crystal due to the diffusion of carbon substances to the crystal.

A half-century practice of diamond synthesis from graphite with a balanced structure of striated and spherical components having a degree of graphitisation in the range g=0,36÷0,44 oted at the same temperature, shows that under similar synthesis conditions are obtained by single-crystal diamond isometric forms (octahedra, cubooctahedrons, Cuba), grains of irregular shape.

The invention is illustrated in the drawing, in which figure 1 shows that the shape of the obtained crystals of diamond depends on how focused the crystallites of needle coke in the sample relative to the isotherm temperature field in the reaction cell. If the coke crystallite in the sample is directed strictly to the radius of the cell (perpendicular to Yateley to the isotherm, it crosses), it turns out crystal diamond right needle shape (figure 1, item 1). If the crystallite coke is positioned so that its long axis is a tangent to the isotherm angle other than 90°we get diamonds elongated, asymmetrical forms (figure 1, item 2). The degree of asymmetry depends on the orientation angle between the long axis of the crystallite and the tangent to the isotherm. In graphite, there is no strict orientation of the crystallites coke, so for one synthesis cycle is a whole gamut of elongated diamond crystals of varying degrees of symmetry. As graphite is used as a binder and even coal tar, from which also comes the synthesis of diamond, Speke after synthesis are present and normal isometric crystals 3. Figure 2 shows the needle diamond in an enlarged scale.

Example 1.

From a monolithic piece of artificial graphite type HSV brand with filler of needle coke was drilled cylindrical rod with a diameter of 10 mm Of rod cut disks with a thickness of 2.4 mm Disks were loaded into the reaction cell, alternating with the catalyst - solvent (Ni, Mn). The cell was placed between two block matrices with grooves, generated pressure in the cell to 4.5 GPA, was heated to a temperature of 1250±50°speed 80÷90°C / min and held at this same time is the temperature value 10 minutes After synthesis, spectra were purified from unreacted graphite by the standard technology of chemical treatment. The result is a 5% diamond right needle shape and about 30% of the crystals are elongated. The rest of the diamonds represented the grains of irregular shape, the twins type dovetail, with rough edges. The maximum size of the crystals along the long axis of 1.0 mm, ratio of length to width is from 3:1 to 6:1.

Example 2.

Same as in app.1, only the diameter of the disks of graphite with needle coke was 8 mm, the Pressure in the reaction cell was brought to 7.0 GPA, temperatures of up to 1300°50÷75°C/min, the result is about 7.5% of the crystals right needle shape and about 40% of the crystals are elongated, various degrees of skewness. The size of the crystals along the long axis lie in the range 0.5-0.8 mm, a width in the range of 0.15-0.20 mm

Technical and economic effect is to replace short supply and expensive natural diamonds XV group "a", VII group G and XXII group "a" in the manufacture of diamond needles on synthetic diamonds needle shape. This eliminates the need for the grinding operation when cut natural diamond crystal octahedral form.

Technical documentation for the synthesis of diamonds according to the technology described in the application, is available in full

The method of synthesis needle and elongated diamond, comprising mixing the mixture of the alloy Mn-Ni-Fe in a weight ratio of 60±5:30±5:10±5 and powder of carbonaceous substances and processing the mixture at a pressure of >40 kbar and T>950°C at a heating rate of less than 100°C/min, wherein the carbonaceous substance use needle coke or graphite-based coke with one-component anisotropic structure with the degree graphitization is not less than 0.55 relative units.



 

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