RU2434977C1 - Procedure for production of diamonds of fantasy yellow and black colour - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure consists in ion-energy-beam processing diamonds with high power ion beam of inert chemical element of helium with dose of radiation within range from 0.2×10¹⁶ to 2.0×10¹⁷ ion/cm² eliminating successive thermal annealing.

EFFECT: production of amber-yellow and black colour of diamond resistant to external factors at significant reduction of material and time expenditures of process of diamond upgrading.

1 dwg, 2 ex

Description

The invention relates to the field of processing (refinement) of natural and synthetic diamonds with the ultimate goal of improving their decorative properties. Namely, the invention provides for colorless diamonds (diamonds) to be persistent yellow or black in color, which will significantly increase their market value and expand the range of these precious stones in the jewelry industry.

Fantasy-colored diamonds, such as amber-yellow, blue, green, pink, red, are extremely rare in nature and valued above all. The price of diamonds in international gem markets is primarily determined by their color. Due to the rarity of such stones, their market is currently very specific, they are often sold through specialized auctions such as Sothebys or Christies. At the same time, brown diamonds are widely used in nature, are relatively inexpensive and are often used as industrial ones in drilling, metalworking, etc. According to Rapaport Diamond Report - 2009, the cost of the most expensive fancy red diamonds can reach 300,000 dollars. per 1 carat (0.2 g). After fancy color diamonds, colorless diamonds have the highest value.

Thus, there is a great financial incentive to ennoblement, i.e. obtaining fancy coloring of diamonds. To date, in the field of gemological refinement of diamonds, a certain scientific and production potential has been accumulated.

A known method of processing diamonds by the action of an electron beam with an integrated flux in the range of 5 × 10 ¹⁵ -5 × 10 ¹⁸ electron / cm and annealing in the temperature range of 300-1900 ° C with simultaneously acting electric field with a voltage of over 10 V / cm is subjected to at least one local region of the crystal to give this region a certain color shade (RF patent No. 2293148, C30B 33/04; C30B 33/02; C30B 29/04; C30B 31/04, 02/10/2007), analogue 1.

The disadvantages of this method are:

 multi-stage processing;

 significant energy and hardware costs;

 the locality of the resulting fantasy coloring of diamonds;

 heterogeneity of the distribution of color across the crystal, which leads to lower prices.

A known method for changing the color of non-decoratively colored natural diamond, including rough cutting of natural diamond to give a streamlined natural diamond, placing said streamlined natural diamond in a pressure transmitting medium, compacting said pressure transmitting medium in a tablet, exposing said tablet to high pressure and high pressure temperature within the region of stability of graphite or within the region of stability of diamond in the carbon phase diagram over time enough to change the color of said diamond; and extracting said diamond (RF patent No. 2279908, B01J 3/00; СВВ 31/06; СВВ 29/04; 07/20/2006), analogue 2.

This method of refinement of diamonds (diamonds) is associated with significant material costs, since it involves simultaneous autoclaving of samples under conditions of ultrahigh pressures and temperatures in the thermodynamic region of stability of diamond and graphite. A significant part of the initial diamond material may be destroyed.

A known method of processing colored diamonds or diamonds to discolor them and relieve additional stresses by physically applying in a closed reaction volume the samples of diamonds or diamonds with high pressure and temperature for a time sufficient to improve their quality, the pressure exerted on the samples is from 6 to 9 GPa in the field of thermodynamic stability, and the temperature during the physical impact is in the range of 1700-2300 ° C, the physical impact on the samples is carried out in a medium of g rafite powder, which filled the reaction volume, temperature heating is carried out by direct exposure to alternating electric current on diamond or diamond samples through graphite powder with a specific electric power of 0.18 kW / cm ³ or more, and the current power gradually increases from zero to the operating value a subsequent decrease and increase in current power at least 2 times with a temporary exposure for each change in electric power, and the output from the annealing process of samples is carried out by a smooth decrease in power current type to zero (RF patent No. 2281350, С30В 33/02; C30B 33/04; C30B 29/04; B01J 3/06; СB 31/06, 08/10/2006), analog 3.

The disadvantages of this method are:

high material costs;

high time costs;

multi-stage process.

A known method for producing fancy red diamonds with stable NV color centers, absorbing in the wavelength range of 400-640 nm, by irradiation with an electron stream and annealing at a temperature of at least 1100 ° C in vacuum, which uses natural type Ia diamond and in its crystalline isolated nitrogen atoms are formed in the lattice in the substitutional position — defects C — by high-temperature treatment in a high-pressure apparatus at a temperature of more than 2150 ° C with a stabilizing pressure of 6.0-7.0 GPa, carried out before irradiation with high an energetic electron flux with a dose of 5 * 10 ¹⁵ -5 * 10 ¹⁸ cm ² at 2-4 MeV when using diamonds containing defects A, or by irradiating a high-energy electron flux with an irradiation dose of more

10 ¹⁹ cm ^-2 when using highly nitrogenous natural diamonds containing more than 800 ppm nitrogen impurities in the form of defects A or B1 (RF patent No. 2237113, C30B 33/04; C30B 33/02; C30B 29/04; C01B 31/006, 27.09 .2004), analogue 4.

The disadvantages of this method are:

significant energy costs

the method is not applicable for absolutely all diamonds and in this regard has certain limitations.

A colored diamond is known in which a single-crystal diamond layer is obtained by chemical vapor deposition, said layer is colored and its thickness is more than 1 mm (RF patent No. 2314368, С30В 25/02; С30В 25/20; С30В 29/04; А44С 17 / 00, 01/10/2008), analog 5.

The principal limitation of this method is the insignificant thickness of the overgrown diamond layer, the limited distribution of the induced fantasy color.

A known method of refinement of diamonds by exposure to electron beams and annealing for a period of time from 30 minutes to several hours to give them certain shades, in which exposure is carried out by electron beams with an integrated electron flux in the range of 5 × 10 ¹⁵ -5 × 10 ¹⁸ cm ^{- 2} , and annealing is carried out either at atmospheric pressure, or in a vacuum, or in an atmosphere of inert gases at 300-1900 ° C, after which they are again exposed to electron beams and annealed, and the process is repeated many times until the desired color is obtained spines (RF patent No. 2145365, С30В 33/04; СВВ 29/04; СВВ 31/06, 02/10/2000), analogue 6.

The method is associated with a frequent undesirable effect of deterioration of the decorative properties of rough diamonds.

A known method of coloring substandard diamonds in black, including heating in a vacuum and exposure to additional physical factors, which use light polychromatic radiation and a magnetic field, while heating and exposure to additional physical factors (RF patent No. 2178814, C30B 33 / 02; С30В 33/04; С30В 29/04; СВВ 31/06, 01/27/2002), analog 7.

The method is energy-consuming, since it is associated with heating, exposure to a magnetic field and polychromatic exposure, as well as the result of this method is to color diamonds only in black.

Known experimental work on the implantation of helium ions into diamond at energies of 350 keV and at doses from 1.0 × 10 ¹⁵ to 1.0 × 10 ¹⁷ ion / cm ² followed by heat treatment of samples at temperatures from 150 ° C to 1600 ° C , in order to form a local graphitized layer and change the optical properties of crystals. In this work, a change in optical properties (namely, blackening due to graphitization and an increase in optical density) occurs only in the near-surface layer with a thickness of up to 100 nm at a depth of 700 nm. However, the authors do not report any data on the change in the initial, colorless color of diamond crystals to yellow. In addition, the proposed method for modifying the optical properties of diamonds included the stage of etching the surface, graphitized zones of implanted crystals in chemically aggressive media (Khomich A.V., Khmelnitsky R.A., Dravin V.A., Gippius A.A., Zavedeev E. V., Vlasov I.I. Radiation damage in diamonds during implantation of helium \\ FTT. 2007. V.49. Issue 9. P.1585-1589).

Summarizing all of the above, it should be noted that all the described methods for refining diamonds are very laborious, require significant material, energy and hardware costs, suggest a complex, multi-stage effect on the processed substrate by various physicochemical methods. Many of these methods cannot be considered environmentally friendly, because The result of hard electromagnetic radiation is often induced radioactivity, which automatically excludes the use of such diamonds in the production, distribution and use of jewelry.

Closest to the claimed method is a method for staining diamonds (diamonds) using the ion implantation method and high-temperature subsequent thermal annealing. The method described in the patent involves, at the first stage, ion-beam treatment (implantation) of either initially colorless or pale yellow colored diamond crystals, with a beam of nitrogen ions with an energy of 70 keV and a dose of 10 ¹⁷ ion / cm ² . The second mandatory step is the post-implantation treatment of implanted diamonds, namely, thermal annealing in vacuum at temperatures of about 650 ° C for 2 hours (US patent No. 7604846 B2, C23C 14/06; C23C 14/14; C23C 14/48; C23C 14 / 58, 10.20.2009).

The disadvantages of this invention is that in the process of implantation, the treated diamonds acquire an uneven (surface), non-decorative only black color, the formation of which is associated with partial amorphization and graphitization of the surface zones of crystals and the formation of precipitate particles of the composition in the diamond structure (C ₃ N ₄ ), which reduces (excludes) the commercial attractiveness of diamonds processed by this method. It is the postimplantation heat treatment stage that leads to the formation of persistent black coloration in diamonds. In addition to nitrogen, the patent contains a number of chemical elements of groups II-VI (B, O, Mg, Al, P, S, etc.), promising, according to the authors, when refining diamonds, and in addition to vacuum medium, the possibilities of thermal annealing of samples are mentioned in an inert atmosphere of helium, nitrogen, argon, etc. However, specific technical results in this case are not given.

The task of the invention is to provide a method for producing fancy yellow and black diamonds, resistant to external factors.

The problem is solved in that in the method for producing fancy diamonds from yellow to black, which consists in ion-beam processing of diamonds with a high-energy ion beam of reactive elements, characterized in that the ion-beam processing of diamonds is carried out by ions of an inert chemical element of helium with a radiation dose of the range from 0.2 × 10 ¹⁶ to 2.0 × 10 ¹⁷ ion / cm ² , with the possibility of eliminating subsequent thermal annealing.

The method is as follows: implantation of accelerated to high energies, for example up to 40 keV, of singly charged He ⁺ ions is carried out on specialized high-energy hardware complexes - the so-called ion-beam accelerators (ILU) at room temperature of the substrate in a residual vacuum, depending on the type (industrial brand) of the accelerator used. The ion current density is within the range of 1-20 μA / cm ² . Depending on the ultimate task of obtaining fancy diamond coloring, the radiation dose varies in the range from 0.2 × 10 ¹⁶ to 2.0 × 10 ¹⁷ ion / cm ² . The time (t) of the actual implantation processing of the samples is determined by the ion current density (j) and a given radiation dose (D) according to the formula

t = (D · e) / j,

where e = 1,60219 × 10 ^-19 C - the positive charge of the ion. When implementing the proposed method, in accordance with the above values of the changes in the values of j and D, the implantation processing time of the samples falls in the range from tenths of a minute to several hours. At minimum radiation doses, diamonds acquire a bright amber-yellow color, and at maximum radiation doses, the crystals turn black. An intermediate amount of interstitial helium ions leads to the appearance of intermediate tan, bright tan, red tan, and tan tones processed by implantation. All of the above color shades of implantation-processed diamonds are highly decorative fantasy type.

The claimed solution is illustrated by the drawing, which illustrates the optical absorption spectra of various diamond samples.

Example 1. A faceted diamond (brilliant) is used originating from the Mir deposit (Yakutia). Weight 0.12 carats, diamond cut Кр-57 of category “A”, colorless (curve A in the drawing), transparent, without visible defects and foreign inclusions. An abnormal birefringence is observed in the polariscope throughout the stone. In the shortwave UV light is inert. Color assessment according to GOST 52913-2008 - “5”, according to the GIA International System - “L”. He ⁺ ions were implanted at room temperature of the irradiated substrate using an ILU-3 ion accelerator in a residual vacuum of 10 ^-5 Torr. Ion-beam treatment modes: energy 40 keV, ion current density I = 3 μA / cm ² , radiation dose 1.0 × 10 ¹⁶ ion / cm ² , implantation time 1 min. Result: the diamond is painted bright yellow with a golden amber tint. When studying in a polarized light a petrographic microscope and in immersion liquids (magnification 35 times), yellow color of high saturation is observed, the stone is uniformly colored throughout. According to the color characteristics of the international system, the GIA is identical to the natural counterpart, Fancy Light Yellow. On a microspectrophotometer in a high-precision “photon counting” mode, optical absorption spectra are recorded in the wavelength range 400-800 nm, which are shown in the figure. The optical spectrum of a fancy bright yellow diamond (curve B) shows intense absorption in the near ultraviolet and infrared spectral regions, as well as absorption bands at 595 and 635 nm in the visible wavelength range. As a result of this, the “transmission window” falls on the yellow wavelength range, which explains the nature of the yellow color of the implanted diamond.

Example 2. A faceted diamond (brilliant) is used originating from the Mir deposit (Yakutia). Weight 0.10 carat, diamond cut Kr-57, category “A”, colorless, transparent, with no visible defects and foreign inclusions. An abnormal birefringence is observed in the polariscope throughout the stone. In the shortwave UV light is inert. Color assessment according to GOST 52913-2008 - “5”, according to the GIA International System - “L”. He ⁺ ions were implanted at room temperature of the irradiated substrate using an ILU-3 ion accelerator in a residual vacuum of 10 ^-5 Torr. Ion-beam treatment modes: energy 40 keV, ion current density I = 3 μA / cm ² , radiation dose 7.0 × 10 ¹⁶ ion / cm ² , implantation time 1 min. Result: The diamond is painted in intense black. When studying in a polarized light a petrographic microscope and in immersion liquids (magnification 35 times), a black color of high saturation is observed, the stone is uniformly colored throughout. In the optical absorption spectrum of fancy black diamond (curve B), there is a significant increase in optical density over the entire visible wavelength range: about 2 times compared with the yellow diamond described in example 1, which leads to an intense black color of the crystal.

In contrast to the above patents and prototype, the proposed method uses ion beams with lower energy and there is completely no post-implantation heat treatment of irradiated diamonds, which together significantly reduces the energy, material and time costs of the process of staining diamonds in the desired colors. In addition, the refinement of diamonds by the proposed method can be carried out directly in the finished jewelry, because the methodology is gentle and is not associated with a violation of the integrity of the gem and the surrounding space.

The color is characterized by a uniform distribution throughout the volume of the crystal (or faceted stone), uniformity, physico-chemical resistance to external influences and environmental cleanliness (absence of any residual radiation.) An independent gemological study of the diamonds processed by the proposed method showed their correspondence and identity natural patterns. For processing by the proposed method, practically all conditional (colorless) and substandard (board, ballas, carbonado) diamonds of both natural and artificial origin are suitable.

The presence of diamond crystals or faceted diamonds named fancy color will significantly increase the cost of rough diamonds and, accordingly, the price of diamond jewelry in the specialized world market of precious stones.

The claimed technical solution meets the criterion of "novelty" presented to the invention, because the claimed combination of features and the achieved technical result is not revealed from the level of solution to this problem that has been studied to date.

The claimed technical solution meets the criterion of "inventive step" for inventions, because it is not obvious to a person skilled in the art.

The claimed technical solution was implemented in laboratory conditions of Kazan State University and the Kazan Physical-Technical Institute of the Russian Academy of Sciences on real diamond samples and can be implemented at any specialized enterprise using standard ILU, which proves the claimed technical solution meets the criterion of "industrial applicability".

Claims (1)

A method for producing fancy diamonds from yellow to black, comprising ion-beam processing of diamonds with a high-energy ion beam of reactive elements, characterized in that ion-beam processing of diamonds is carried out by ions of an inert chemical element of helium with a radiation dose in the range of 0.2 · 10 ¹⁶ to 2.0 · 10 ¹⁷ ion / cm ² with the possibility of eliminating subsequent thermal annealing.

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