Method of growing diamond monocrystal

FIELD: crystal growth.

SUBSTANCE: method comprises separating the inoculation from the source of carbon by a metal-dissolver made of an alloy of ferrous, aluminum, and carbon when a 20-30°C temperature gradient is produced between the carbon source and inoculation. The growth zone is heated up to a temperature higher than the melting temperature of the alloy by 10-20°C, and the melt is allowed to stand at this temperature for 20 hours. The temperature then suddenly increases above the initial temperature by 10-25°C and decreases down to the initial value with a rate of 0.2-3 degree per minute.

EFFECT: improved quality of crystal.

1 tbl, 2 ex

 

The invention relates to the field of growing diamond single crystals, in particular large high-quality nitrogen-free, intended for the manufacture of diamond anvils of high-pressure cells for studies of phase transitions and properties of various substances at high pressures by the method of Raman scattering (CRS).

For these purposes, can be used natural nitrogen-free diamonds of type IIa, however, their number among all mined diamonds does not exceed 2%. Given that the diamonds are of this type used for the manufacture of diamonds, their cost is high. In addition, the large number of defect-free crystals, suitable for the manufacture of products with a diameter of 6-8 mm, very small. Thus, the use of natural diamonds are type IIa cannot meet the needs of science and technology in diamond crystals of the desired quality and size.

Fairly large, weighing several carats, the diamond single crystals can be grown with the use of equipment high pressure.

A method of obtaining single crystals of diamond in high-pressure apparatus (RTH) using temperature gradient, in which the source of carbon (graphite or diamond) is located in a region with a higher temperature, and the seed crystal, separated from the source of carbon with a layer of molten metal-rest is ritala, is located in the area with less than a high temperature. The carbon source is soluble in the molten metal diffuses through the melt and is deposited on the seed crystal in the form of a diamond (US 4340576, SW 31/06, pub. 20.07.1982).

Also known is a method of obtaining single-crystal diamond by the method of temperature gradient on the crystal, the seed crystal in a melt of metal-solvent selected from the group of cobalt, Nickel, iron, chromium and manganese, including heating in the area of diamond stability at initial pressure of more than 4 HPa and shutter, wherein the exposure is carried out at the joint temperature change up to 10% of the initial synthesis temperature and increased pressure in the range of 1-5% of the initial value (EN 2192511 C1, SW 29/04, 01J 3/06, SW 31/06, pub. 10.11.2002). This method allows you to obtain the single-crystal diamond weighing 2.72 carats. However, according to this method can be obtained diamonds only with high (50-200 parts per million (ppm)) impurity content of nitrogen, which causes a strong absorption at wavelengths less than 550 nm, which limits their use as a material for the manufacture of diamond anvils.

To obtain diamond single crystals with a low concentration of an impurity of nitrogen must be added to the growth medium a substance that can bind nitrogen in the reaction volume (Goethe is nitrogen), and preventing its incorporation into the lattice of the growing diamond.

The closest known analogues technical solution chosen as a prototype, is a method of growing diamond single crystals containing inclusions of metal in a concentration of not more than 0.5 wt.% and nitrogen in an amount of not more than 0.1 ppm, while the growth rate of not less than 2 mg/hour, using temperature gradient, which uses a source of carbon, a metal-solvent and the seed crystal, the source of carbon is separated from the seed crystal metal-solvent, a source of carbon dissolved in the metal-solvent by heating, between the carbon source and the seed crystal, there is a temperature gradient, and the temperature and pressure are such that the potential growth of diamond seed crystal. In this way as a metal-solvent is used, the alloy containing iron and at least one component selected from the group comprising cobalt, Nickel, manganese and chromium, and also containing from 0.1 to 6 wt.% of carbon. As nitrogen getter is used, at least one metal selected from the group comprising titanium, zirconium, hafnium, vanadium, niobium and tantalum in an amount of from 0.5 to 7 wt.% the weight of the metal-solvent. To reduce capture the growing crystal inclusions of metal-solvent ROSTO the second medium is added, at least one metal with a low viscosity selected from the group comprising aluminum, tin, indium, gallium, silver, copper, cesium, lead, antimony and zinc in an amount of from 0.5 to 3 wt.% the weight of the metal-solvent (US 6,129,900, 01J 3/06, pp.. 10.10.2000). This method allows you to obtain the single-crystal diamond weighing 8 carats related to type IIa, suitable for the manufacture of diamond optical elements infrared range. However, the growth of crystals by this method is carried out using the alloys of the metal-solvent containing as components of cobalt and Nickel, the atoms are in contrast to the iron atoms are seamlessly integrated into the lattice of the growing crystal as a structural impurities, located in the growth sectors {111} (Jia H., Hayakawa, S., Li W. et al. Cobalt impurities in synthetic diamond is Diamond and Related Materials, 1999, 8, R-1899). This leads to changes in the electronic structure of diamond and causes the formation of bands in the luminescence spectra, the intensity of which increases with decreasing crystallization temperature (Kanda H., Watanabe K. Distribution of the cobalt-related luminescence center in HPHT diamond - Diamond and Related Materials, 1997, 6, R-711). Crystals grown by this method cannot be applied for the manufacture of diamond anvils of high-pressure cells used in the studies of the properties of materials using cattle as their own luminescence prevents floor is to obtain reliable information on the Raman spectra of the investigated material. Research of the authors of the patent, selected as a prototype for growing diamonds for use as a metal-solvent system alloys iron-aluminum-carbon, showed that a significant decrease in the impurity concentration of nitrogen in the crystal the concentration of aluminum than 4 wt.%, this increase in crystal growth rate above 1 mg/h leads to an increase in the concentration of metallic impurities and significantly affects the quality of the crystals. When reducing the concentration of aluminum in the alloy was possible to grow crystals with a higher speed while maintaining their quality, but not enough nitrogen getter in this case led to a rise in the concentration of nitrogen impurities in crystals.

The technical result of the invention consists in the cultivation of large diamond single crystals containing a reduced concentration of nitrogen impurities, metallic impurities and low intensity luminescence, suitable for the manufacture of diamond anvil pressure.

The technical result is achieved by a method of growing diamond single crystals in the region of its thermodynamic stability on the seed crystal, which is separated from the source of carbon with a metal-solvent, which is used as an alloy of iron, aluminum and plastics technology : turning & the Yes, when creating a temperature gradient between the carbon source and the seed crystal 20-30°With an alloy of iron, aluminum, and carbon taken in the following ratio, wt.%: iron - 89-92, aluminum - 4-6, carbon - 4-5, heating is carried out until the starting temperature in the growth zone, the value of which 10-20°C above the alloy melting temperature of the metal-solvent, produce exposure at this temperature for up to 20 hours, and then spend a recurrent cycles of temperature changes, including the stage of the stepwise temperature increase by 10-25°and above the initial step of lowering the temperature to the initial speeds of 0.2 to 3 degrees per minute.

If all these conditions grow diamond crystals weighing more than 3 carats with the mass growth rate of more than 2 mg/hour, the Crystals contain not more than 0.1 ppm nitrogen impurities, not more than 0.5 wt.% metallic impurities are luminescence intensity is 2-3 times lower than the crystals grown by the method selected as the prototype.

It is found experimentally that when the time consuming process of crystallization of less than 20 hours spent in the system iron-aluminum-carbon at a constant temperature, when the growing crystal diamond has a sufficiently small size, the capture of metallic impurities in the volume, except for a small area near his summe is zi seed, does not occur. Increasing the duration of crystallization is observed cyclic capture the growing crystal metallic impurities, the concentration of which is up to 4 wt.%. From the data obtained in practice, it follows that to reduce the probability of capture of inclusions while maintaining a sufficiently high growth rate it is necessary to periodically dissolving the surface layer of the growing diamond crystal by an abrupt temperature increase with subsequent slow it down to the initial value.

When the content of aluminum is less than 4 wt.% the weight of the metal-solvent-concentration impurity nitrogen in the resulting diamond crystals exceeds 0.1 ppm, and with more than 6 wt.% there is a stratification of molten metal solvent into two immiscible phases and growth of diamond seed crystal does not occur. When the carbon content is less than 4 wt.% the weight of the metal-solvent there is frequent dissolution of the seed crystal, and when more than 5 wt.% there is often a parasitic growth spontaneously formed crystals of diamond, competing with the growth of the crystal core, reducing its final weight. When heated to an initial temperature of less than 10°C above the alloy melting temperature of the metal-solvent, the rate of crystal growth is less than 2 mg/hour and the concentration of meta is symbolic inclusions in the resulting crystal is greater than 0.5 wt.%. When heated to the initial temperature by more than 20°exceeding the melting temperature of the alloy of the metal-solvent, and carrying out further process of growing simultaneously at maximum temperature difference between the carbon source and the seed crystal and the magnitude of the abrupt increase of the temperature, the concentration of nitrogen impurities in the grown crystals may exceed 0.1 ppm. After a sudden temperature rise of less than 10°With the concentration of metallic impurities in the obtained crystal is greater than 0.5 wt.%, and after a sudden temperature increase of more than 25°With the concentration of nitrogen impurities in crystals grown at the maximum values of the initial overheating relative to the melting temperature of the alloy of the metal-solvent and the temperature difference between the carbon source and the seed crystal, exceed 0.1 ppm. When the rate of temperature decrease of less than 0.2 degrees per minute and more than 3 degrees per minute, the concentration of metallic impurities in the crystal exceeds 0.5 wt.%.

The following examples illustrate the practical implementation of the method.

Example 1. In the reaction cell volume high pressure place the puck source of carbon with a diameter of 15 mm, a height of 2.75 mm graphite purity 99,9995%; under it place the washer SPL is and the metal-solvent with the following ratio of components, wt.%: iron - 90, aluminum - 5, C - 5, diameter 15 mm, height of 4.5 mm, the Seed single crystal diamond size of 0.5 mm guide face (100) parallel to the plane of the washer metal-solvent and pressed into a substrate of cesium chloride, which is placed under the metal washer solvent.

The temperature difference between the carbon source and the seed crystal (growth zone) set upper and lower end of heaters of different heights, made from a mixture of graphite and Zirconia.

The assembled cell was placed in the RTH type "donut", which is placed in the working space of the hydraulic press TO 044. Create pressure in the reaction volume of 5.5 GPA and running automated system of control of crystallization processes increase the input electric power to a value that ensures the achievement of temperature in the growth zone 10°C above the alloy melting temperature of the metal-solvent, when the temperature difference between the carbon source and the seed crystal 20°C. the Specified mode support 18 hours. Then, under the control of the automated system of control of the crystallization process carried out stepwise increase of the electric power supplied at 40 watts, providing a temperature increase of 30°C. Further, under the control of automates the trated system control the crystallization process carried out even decrease the electric power supplied 30 minutes, providing lower temperature in the reaction volume at a rate of 1 degree per minute.

Similarly repeat the rounds, "sharp heat-smooth cooling 400 times. Shut off supply of electric power, lower pressure, relieve RTH, extract the reaction cell. Separate washer metal-solvent grown diamond and dissolve the metal in a mixture of hydrochloric and nitric acids. Remove the grown diamond. The weight of the crystal 682 mg (3,41 carats). The total duration of the process of growing amounted to 218 hours, and the average mass rate of growth of 3.13 mg/h of the Crystal without inclusions in the volume, with the exception of three small inclusions in the area of the seed. The amount of metallic impurities, measured using magnetic scales GENEQ MSB AUTO, is 0.32 wt.%. The impurity concentrations of nitrogen (Nccalculated by the value of the absorption coefficient at 270 nm α270in the spectrum recorded on the spectrometer CARY 4000:

Nc[ppm]=0.517 α270[cm-1],

is 0.08 ppm. The excitation of the luminescence and Raman scattering spectrum of diamond is carried out at room temperature by radiation of an argon laser with a wavelength of 514.5 nm. Registration of the spectra is performed on the spectrometer JY TRIAX 552A, equipped with a cooled CCD-matrix. The intensity of luminescence of the crystal To that estimated by the method of vnutrennih the standard value of the maximum of the Raman peak of the second order in the diamond at 2467 cm -1I2467to the average value of the background luminescence, measured at 1000 (I1000) and 3000 (I3000) cm-1according to the formula:

K=2I2467/(I1000+I3000);

has a value of 11.3. The higher the value, the weaker luminescence of the crystal.

Example 2. In the reaction cell volume high pressure place the puck source of carbon with a diameter of 15 mm, a height of 2.75 mm, graphite purity 99,9995%; under it put the puck alloy metal-solvent with the following ratio of components, wt.%: iron - 91; aluminum - 4 and carbon - 5, diameter 15 mm, height of 4.5 mm, the Seed single crystal diamond size of 0.5 mm, Orient the face (100) parallel to the plane of the washer metal-solvent and pressed into a substrate of cesium chloride, which is placed under the metal washer solvent. The temperature difference between the carbon source and the seed crystal (growth zone) set upper and lower end of heaters of different heights, made from a mixture of graphite and Zirconia.

The assembled cell was placed in the RTH type "donut", which is placed in the working space of the hydraulic press TO 044. Create pressure in the reaction volume of 5.5 GPA and running automated system of control of crystallization processes increase the applied electric power to the extent of providing the first temperature in the growth zone, on 20°C above the alloy melting temperature of the metal-solvent, when the temperature difference between the carbon source and the seed crystal 20°C. the Specified mode support 15 hours. Then, under the control of the automated system of control of the crystallization process carried out, a sharp increase in electrical power input of 20 watts, providing a temperature increase of 15°C. Further, under the control of the automated system of control of the crystallization process carried out even decrease the electric power supplied at 20 watts for 10 minutes, allowing the temperature decrease in the reaction volume with the speed of 1.5 degrees per minute.

Similarly repeat the exercise cycles "sharp heat-smooth cooling 1500 times. Shut off supply of electric power, lower pressure, relieve RTH, extract the reaction cell. Separate washer metal-solvent grown diamond and dissolve the metal in a mixture of hydrochloric and nitric acids. Remove the grown diamond. The weight of the crystal 608 mg (3.04 from CT). The total duration of the process of growing amounted to 265 hours, and the average mass growth rate - to 2.29 mg/H. the Crystal contains one small inclusion in the peripheral part and four small inclusions in the area of the seed crystal. The amount of metal the ski inclusions is 0.48 wt.%. The impurity concentrations of nitrogen (Ncis 0.06 ppm. The intensity of luminescence of the crystal To has a value of 12.4.

Other examples, including the method selected as the prototype shown in the table.

Thus, the proposed method of growing diamond single crystals allows you to get the crystals weighing more than 3 carats, with a low intensity luminescence containing an admixture of nitrogen is not more than 0.1 part per million, and metal inclusions is not more than 0.5 wt.%, when the mass growth rate of more than 2 mg/h

Received the diamond single crystals were used for the manufacture of diamond anvil pressure to study the properties of materials by the method of Raman scattering of light.

Table
OptionsExample 3Example 4Example 5An example of the prototype 1Example prototype 2
The composition of the alloy-solvent, wt.%Fe-90

Al-6

C-4
Fe-91

Al-4

C-5
Fe-90

Al-4

S-6
Fe-52,

With-41,

Al-2,

C-5
Fe-33,

Ni-60,

Al-2,

C-5
Pressure, HPa5,55,55,55,5 5,5
The excess of the initial temperature above the melting point of the metal-solvent °C1015202020
The temperature gradient °2030302020
Exposure at the initial temperature, h181515200200
Temperature rise, °102015nono
The speed of the temperature, deg/min30,50,2nono
The number of cycles "heating-cooling"5500420200nono
The weight of the crystal mg665764710649703
The duration of the growth process, h323,6295265200200
The average mass growth rate, mg/hto 2.062,592,683,253,52
Metal inclusions, wt.% 0.470.490,360,43
The concentration of nitrogen, ppm0,060,090,100,060,08
The intensity of the luminescence13,811,213,15,24,4

A method of growing diamond single crystals in the region of its thermodynamic stability on the seed crystal, which is separated from the source of carbon with a metal-solvent, which is used as an alloy of iron, aluminum, and carbon, when creating a temperature gradient between the carbon source and the seed crystal 20-30°C, characterized in that the alloy of iron, aluminum, and carbon taken in the following ratio, wt.%:

iron89-92
aluminum4-6
carbon4-5,the

the heating is carried out until the starting temperature in the growth zone, the value of which 10-20°C above the alloy melting temperature of the metal-solvent, produce exposure at this temperature for 20 h, and then carried out periodically repeated cycles of temperature changes, including the stage of the abrupt increase the temperature by 10-25° With the above primary and the step of lowering the temperature to the initial speeds of 0.2 to 3 degrees per minute.



 

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3 cl, 9 dwg, 4 ex

FIELD: carbon materials.

SUBSTANCE: invention relates to electrochemistry of carbon materials, namely to removing carbon-containing impurities from diamond powders. Method comprises electrochemical treatment of diamond powder in sulfuric acid electrolyte, more specifically in sulfuric acid solution of manganese sulfate while electrochemical treatment is effected at concentration of manganese in electrolyte 15-30 g/L, solids/liquids ratio 1:(3-5), anodic current density 0.10-0.20 A/cm2. and temperature 125 to 170°C for 2 to 7 h. Degree of purification reaches 99.8%.

EFFECT: increased degree of removing residual graphite under relatively low temperature preventing oxidation of diamond.

1 tbl, 7 ex

FIELD: production of nanodiamond suspensions in various media for conducting of plating processes.

SUBSTANCE: method involves providing thermal processing of nanodiamond powder in air at temperature of 440-600 C until powder weight losses reach 5-85%. Thermally processed powder forms stable suspensions in water, ethyl alcohol and other solvents upon common mixing. Sediment stability of nanodiamond suspensions thermally processed in accordance with invention and produced using supersonic treatment is at least 1.5 times as high as similar parameter of nanodiamond suspensions produced by prior art processes.

EFFECT: simplified method allowing stability of nanodiamond suspension in various media to be improved.

3 ex

FIELD: chemical industry; cutting tool industry; mechanical engineering; methods of the production of the artificial highly rigid materials.

SUBSTANCE: the invention is pertaining to production of the artificial highly rigid materials, in particular, diamonds, and may be used in chemical industry; cutting tool industry; mechanical engineering, boring engineering. The method provides for compaction of the powdery carbon-containing materials in the field of the quasi-equilibrium state of the graphite-diamond system and the slow refrigeration in the zone of the thermodynamic stability of the diamond or other synthesized material. The heated capsule made out of tungsten with the pure carbon raw fill in with the liquid silicon at the temperature of 1750°K, hermetically plug up, then reduce the temperature to 1700°K during 30-40 minutes and cool to the room temperature within 5-6 hours in the process of the synthesis of the high-strength materials. The monocrystals of the boron carbide of the 400-450 microns fraction and the diamonds of the 40 microns fraction have been produced. The technical result of the invention consists in improvement of the quality, the increased sizes of the monocrystals, and also in the decreased labor input of the production process.

EFFECT: the invention ensures the improved quality and the increased sizes of the produced monocrystals, the decreased labor input of the production process.

2 cl, 2 ex

FIELD: electrochemical extraction of metals from complex compounds; purification of diamond synthesis products.

SUBSTANCE: proposed method includes electrochemical treatment of synthesis product in acid electrolyte for obtaining graphite-diamond product containing 0.5-2.0% of metallic admixtures and deposition of metallic nickel and manganese on cathode. During purification of diamond synthesis products at extraction of nickel and manganese in form of metallic product, electrochemical treatment is carried out in membrane-type electrolyzer at circulation of catholyte through second electrolyzer. Process is conducted in area of temperatures of 25-30°C at cathode current density in the first electrolyzer of 2-15 A/dm2 and 15-30 A/dm2 in the second electrolyzer; catholyte pH in the presence of 100-150 g/l of (NH4)2SO4 in it is maintained at outlet from the first electrolyzer of 5-7.5 and 2.5-5 at return.

EFFECT: possibility of performing nickel and manganese extraction and purification of diamond synthesis products in one cycle.

1 tbl, 6 ex

FIELD: treatment of diamonds.

SUBSTANCE: proposed method of change of diamond color includes the following stages: (i) forming reaction mass at presence of diamond in pressure-transmitting medium fully surrounds the diamond; (ii) subjecting the reaction mass to action of high temperature and pressure during required period of time; proposed diamond is brown diamond, type IIa; its color is changed from brown to colorless by subjecting the reaction mass to action of temperature of from 2200°C to 2600°C at pressure of 7.6 Gpa to 9 Gpa.

EFFECT: possibility of keeping diamond intact during treatment.

46 cl, 4 dwg, 1 ex

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

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