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INVENTION
Patent of the Russian Federation RU2237113
METHOD OF OBTAINING DIAMONDS OF FANTASY RED COLOR
Applicant's name: Vince Victor Genrikhovich (RU)
The name of the inventor: Vince Victor Genrikhovich (RU)
The name of the patent owner: Vince Victor Genrikhovich (RU)
Address for correspondence: 630058, Novosibirsk, ul. Russian, 43, V.G. Vince
Date of commencement of the patent: 2003.06.26
The invention relates to the processing (refinement) of diamond to give them a different color and can be used in the jewelry industry. The method consists in the formation of isolated nitrogen atoms in the substitution position - defects C in the crystal lattice of a natural diamond of type Ia containing defects A or natural high-nitrogen type Ia diamond containing more than 800 ppm of nitrogen impurities in the form of defects A or B1 . A natural diamond of type Ia containing defects A is annealed in a high-pressure apparatus at a temperature of more than 2150 ° C with a stabilizing pressure of 6.0-7.0 Gpa , then irradiated with an electron beam of 5 × 10 15 -5 × 10 18 cm -2 at 2 -4 MeV and subjected to annealing in vacuum at a temperature of not less than 1100 ° C. A natural high-nitrogen type Ia diamond containing more than 800 ppm of nitrogen impurities in the form of defects A or B1 is irradiated with a high-energy electron beam with an irradiation dose of more than 10 19 cm -2 and annealed in vacuum at a temperature of not less than 1100 ° C. Get fancy red diamonds for diamonds with stable NV color centers, absorbing in the wavelength range of 400-640 nm .
DESCRIPTION OF THE INVENTION
The invention relates to the processing (refinement) of diamonds for imparting to them a different coloring, in particular giving a unique fancy red color to natural diamonds, and can find application in the jewelry industry.
A method is known for producing diamonds of red-yellow and black shades , based on the principle of color imposition, i. E. Obtaining the desired color by mixing in a sample of natural color with an electron beam "deposited" by an electron beam in the range 5 × 10 15 -5 × 10 18 cm -2 and annealing at 300-1900 ° C for a time of 30 minutes to several hours, Pressure, and in ultrahigh vacuum or pulsed heating. The process is repeated repeatedly to obtain the desired color ( RU 2145365 C1, 10.02.2000 ).
Modern conventional physical classification of diamonds into types is described in a large number of scientific literature (for example, Walker John Optical absorption and luminescence in diamond - Reports on Progress Physics, 1979, v.42 ) and subdivides diamonds into four types:
- IIa - low-nitrogen diamonds . The main classification features: Absence of absorption in the infrared region of the spectrum, a pronounced edge of fundamental absorption in the ultraviolet region of the spectrum at 225 nm . Diamonds of this type are quite rare, their content does not exceed 2% of the total mass of natural diamonds ;
- IIb - blue semiconductor diamonds . Contain even less nitrogen than diamonds IIa . The blue color and semiconductor properties are due to the impurity of boron. The form of the entry of boron is an isolated atom in the position of substitution;
- Ia is the most common type of natural diamonds (up to 98%) , containing up to 0.3 atomic percent nitrogen. The most frequently encountered forms of the entry of impurity nitrogen are defects A, which are a close nitrogen pair in the neighboring sites of the crystal lattice, and defects B1 , which are four nitrogen atoms around the vacancy;
- Ib - the most rare (less than 0.2%) occurring in nature diamonds and make up the majority of synthetic diamonds . Isolated nitrogen atoms (defects C ) contain a substitutional impurity in an amount of up to 0.05 atomic percent (about 5-6 ppm ). The absorption band associated with defects C begins in the visible region, about 500 nm , and is amplified toward short wavelengths, causing a yellow coloration of type Ib diamonds .
It is known that crystals giving part of impurity nitrogen in the form of isolated replacement atoms (defects C ) are isolated using optical spectroscopy methods to give the diamond various shades of red among the whole variety of natural diamonds. According to the physical classification of diamonds into types, such crystals can be assigned either to type Ib, or to mixed types Ia + Ib or Ib + Ia . In the work ( Collins AT, Irradiated typed Ib diamond - J.Phys.C: Solid State Phys., 1978, v.11, 10, L417-L422 ), the fundamental processes of the transformation of defects in the crystal lattice of diamond Type Ib under irradiation with a stream of high-energy electrons ( 10 22 m -2 / 2 MeV ) and subsequent annealing in vacuum ( 800 ° C, 2 h ). In the process of irradiation, a large number of primary radiation defects arise: vacancies and interstitia. Subsequent high-temperature annealing in vacuum provides stable NV color centers, which are isolated nitrogen atoms at the substitution position with vacancies in neighboring lattice sites. Such defects have absorption in the red region of the spectrum at wavelengths less than 640 nm (1.945 eV) and cause a different intensity of the red color of the diamond crystals.
A method for producing a purple diamond diamond based on a synthetic diamond is known . ( US 4,950,463 A, August 21, 1990 ). According to this method, a synthetic diamond type Ib with a nitrogen content of C defects in the range 8 × 10 17 -1.4 × 10 19 at / cm 3 (or 4.5 to 80 ppm) is irradiated with an electron beam in the range of 5 × 10 16 -2 · 10 18 cm -2 at 2-4 MeV , followed by annealing in vacuum at least 10 -2 torr at a temperature of 800-1100 ° C for more than 20 hours . Purple diamond crystals with NV color centers having an absorption in the range of 500-640 nm at a peak of 570 nm are obtained.
However, as established from the analysis of the luminescence excitation spectra in the work of Vince VG. (Spectroscopy of optically active defects in synthetic diamond - Author's Abstract of Candidate of Physical and Mathematical Sciences, Minsk, 1989, 21 pp.) , NV centers absorb in the range of 400-640 nm . And this absorption in type Ib diamonds is superimposed on the absorption of defects C , beginning and increasing at wavelengths less than 500 nm . As a result, the total absorption spectrum of diamond type Ib with NV centers lies in the wavelength range 400-640 nm .
It is an object of the invention to provide such a method for producing a fantasy red diamond that would allow obtaining in the crystal lattice of natural diamond type Ia stable NV color centers having absorption in the red region of the spectrum at wavelengths of 400-640 nm .
For this, crystals of natural diamond type Ia are used and in its crystal lattice isolated nitrogen atoms are formed at the substitution position-defects C , are irradiated with a high-energy electron flux and subjected to high-temperature annealing in a vacuum.
In this case, the natural diamond type Ia contains an admixture of nitrogen in the form of defects A or is highly nitrogenous and contains an admixture of nitrogen in the form of defects A or B1 with a concentration of more than 800 ppm .
A natural diamond of type Ia , containing an admixture of nitrogen in the form of defects A , is preliminarily subjected to high-temperature annealing in a high-pressure apparatus at a temperature of more than 2150 ° C and a stabilizing pressure of 6.0-7.0 Gpa (the so-called HPHT treatment), then irradiated with a high-energy flow Electrons 5 · 10 15 -5 · 10 18 cm -2 , preferably 10 cm -2 at 2-4 MeV, and subjected to high-temperature annealing in a vacuum at a temperature of not less than 1100 ° C.
A natural high-nitrogen type Ia diamond containing an admixture of nitrogen in the form of defects A or B1 with a concentration of more than 800 ppm is treated with a high-energy particle flux, for example electrons, with an irradiation dose of more than 10 19 cm -2 and subjected to high-temperature annealing in vacuum at a temperature of not less than 1100 ° C.
Our experimental data indicate that when HPNT is treated with a natural diamond type Ia containing an admixture of nitrogen in the form of defects A (a pair of nitrogen in neighboring lattice sites), at a temperature of more than 2150 ° C, approximately 15-20% of defects A are dissociated with formation of Along with other defect defects C in a concentration of at least 10 ppm . As shown by previous studies, given in Insom VG. (Change in the color of brown natural diamonds under the influence of high pressures and temperatures, Notes of the All-Russian Mineralogical Society, 2002, 4, pp. 112-119) , at lower temperatures of HPNT processing (less than 2150 o C ) dissociation of defects A and, accordingly, the formation of defects C not happening. Defects C , formed at temperatures of HPNT treatment of more than 2150 o C , it is quite sufficient that in the course of the irradiation with the electron beam and the high-temperature annealing of diamonds in vacuum, stable NV centers of color formed having absorption in the red region of the spectrum at wavelengths 400 -640 nm and providing the diamond with various shades of fantasy red color.
The mechanism of the appearance of defects C in the crystal lattice of diamond C under irradiation of natural highly-nitrogenous type Ia , containing an admixture of nitrogen in the form of defects A (nitrogen pair at adjacent lattice sites) or B1 (four nitrogen atoms around the vacancy) with a concentration of more than 800 ppm , high doses of high-energy Particles, for example electrons, is associated with the displacement of the nitrogen atoms forming part of the defects A and B1 into an interstitial position. During the subsequent after irradiation of high-temperature annealing, interstitial nitrogen atoms annihilate with vacancies, forming isolated nitrogen atoms in the position of substitution, i.e. Defects C. And absorption in a narrow band of 1346 cm -1 due to defects C was observed. That is, in the crystal lattice of a diamond, along with interstitial nitrogen atoms, isolated nitrogen atoms appear in the position of substitution, defects C. The concentration of defects C is about 5 ppm . Then the defects C thus formed capture occupations, forming stable NV color centers, having absorption in the red region of the spectrum at wavelengths not exceeding 640 nm and providing the diamond with various shades of fantasy red color.
All the changes in the set and concentration of optically active defects, such as A, B1, C, N3, H3 and NV , in the crystal lattice of the diamond were determined from the intensity of the corresponding absorption bands in the infrared, visible and ultraviolet regions of the spectrum.
Examples of the method for obtaining diamonds of a fantasy red color with stable NV color centers, absorbing in the wavelength range 400-640 nm .
Example 1
A 1.84 carat natural diamond crystal is used, initially containing impurity nitrogen in the form of defects A at a concentration of 92 ppm , and defects B1 at a concentration of 258 ppm . In the infrared absorption spectra, bands of 1370 and 1430 cm -1 due to "pleatelites" and a narrow line of 3107 cm -1 due to impurity hydrogen defects were observed. In the visible range of the spectrum at wavelengths below 650 nm , a monotonic increase in absorption toward short wavelengths was observed. Weak absorption systems of 415 nm and 503 nm due to N3 and H3 defects were observed. By the form of the absorption spectra and the set of impurity defects, the crystal uniquely corresponded to type Ia diamonds . The diamond is subjected to HPHT treatment in a high-pressure apparatus at a temperature of 2150 ° C and a pressure of 7 GPa for 10 minutes . During HPNT treatment, the concentration of defects A decreased to 71 ppm , the concentration of defects B1 remained at the same level and formed about 20 ppm of defects C.
The absorption intensity associated with the "pleatelites" decreased three-fold; Absorption, associated with impurity hydrogen, was no longer observed. In the visible range of the spectrum, there was an increase in absorption at wavelengths less than 550 nm . The transmission edge was at 423 nm . In the spectra there were systems: 503 nm - very weak intensity and 990 nm in the near infrared region. The color of the crystal after HPNT treatment became greenish-yellow. On a set of impurity defects, the crystal was already defined as a diamond of the mixed Ia + Ib type.
Then the crystal is irradiated with electrons of energy 3.0 MeV and a dose of 10 18 cm -2 . Irradiation with such parameters creates in the crystal lattice of diamond about 10 ppm vacancies, which coincides with the data obtained on synthetic diamonds, given by Vince VG. (A change in the color of synthetic diamonds due to irradiation with fast electrons and subsequent annealing.) Vestnik Gemmologii, 2002, 2 (5), p . 19-33) . The color of the crystal after irradiation was opaque dark green. Then, the diamond is placed in an evacuated quartz ampoule in which it is annealed for 24 hours at 1100 ° C. During the annealing process, due to migration of vacancies and their capture by isolated nitrogen atoms, 1.5 to 2.0 ppm NV color centers were formed in the crystal. Absorption of NV color centers, observed at wavelengths less than 640 nm , with a maximum at 570 nm , was superimposed on the initial (before irradiation with fast electrons and subsequent annealing) absorption with a transmission edge at 423 nm , which determined the final color of the diamond crystal , which was determined as Intense fantasy purplish red.
Example 2
A natural diamond crystal with a mass of 2.948 carats containing defects A was used with a concentration that did not allow recording the infrared absorption spectra. A 0.236-carat piece is cut from it, and two plane-parallel plates 0.2 and 0.3 mm in thickness are made from this piece. The concentration of defects A in both plates was about 800 ppm . In the infrared absorption spectra, one system of bands with the most intense band of 1282 cm -1 , characteristic of diamonds of type Ia , containing defects A, was observed. The absorption edge was in the ultraviolet region of the spectrum at 300 nm . Absorption in the visible range was absent. Both plates are irradiated with a stream of high-energy electrons ( 3.0 MeV, 10 19 cm -2 ). During the irradiation, the plates are completely black in opaque color. After irradiation, the plates are annealed in a vacuum quartz ampoule at a temperature of about 1100 ° C for 24 hours. Annealing restored the transparency of both plates, giving them an intense fantasy violet-red color.
In the infrared absorption spectra, in addition to the band system associated with defects A, absorption was observed in the band 1450 cm -1 , which is associated with the appearance in the spectra of a single interstitial nitrogen atom, which is also described for synthetic diamond crystals (Malogolovets VG Studying the impurity composition and Real structure of synthetic diamonds by spectroscopic methods.Thesis abstract of candidate of physical and mathematical sciences, Kiev, IPM of Ukrainian Academy of Sciences, 1979, 21 p.) . And absorption in a narrow band of 1346 cm -1 due to defects C was observed. That is, in the crystal lattice of diamond along with interstitial nitrogen atoms, isolated nitrogen atoms appeared in the substitution position (defects C ). The concentration of defects C was about 5 ppm, and an intense absorption system of 640 nm appeared in the visible spectral range, indicating the formation of NV color centers.
After staining both plates in red, similar technological procedures were made with the remaining large piece of diamond weighing 2.712 carats . He changed his color from the initially transparent to the intense fantasy violet-red.
Thus, the proposed method can be used to produce diamonds of fantasy red color, suitable for making diamonds. According to this method, it is possible to process (ennoble) all natural diamonds of type Ia that do not contain in the initial state an admixture of nitrogen in the form of defects C , but having in any concentrations an admixture of nitrogen in the form of defects A and / or B1 .
CLAIM
A method for obtaining diamonds of a fantasy red color with stable NV color centers absorbing in the wavelength range 400-640 nm by irradiating with an electron beam and annealing at a temperature of not less than 1100 ° C in a vacuum, characterized in that a natural diamond of the type Ia is used and in its The crystal lattice forms isolated nitrogen atoms at the substitution position - defects C - by high-temperature treatment in a high-pressure apparatus at a temperature of more than 2150 ° C at a stabilizing pressure of 6.0-7.0 Gpa , performed before irradiation with a high-energy electron flux with a dose of 5 × 10 15 -5 · 10 18 cm -2 at 2-4 MeV using diamonds containing defects A or by irradiation with a high-energy electron flux with an irradiation dose of more than 10 19 cm -2 using high-nitrogen natural diamonds containing more than 800 ppm of nitrogen impurities in the form of Defects A or B1 .
print version
Date of publication 19.11.2006гг
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