Method of change of diamond color at high temperature and high pressure

FIELD: treatment of natural diamond for change of its color.

SUBSTANCE: proposed method includes the following stages: (i)forming of reaction mass at presence of diamond pressure-transmitting medium which fully surrounds it; (ii) action on reaction mass by high temperature and pressure during required period of time; proposed diamond is brown diamond, type IIa; its color is changed from brown to rose by action on reaction mass by temperature from 1900°C to 2300°C at pressure from 6.9 GPa to 8.5 GPa.

EFFECT: enhanced efficiency of enriching diamond color keeping its crystals intact.

30 cl, 4 dwg, 1 ex

 

Background of invention

This invention relates to a method of changing the color of the diamond.

Diamonds usually are divided into four main types: Ia, Ib, IIa and IIb. These types usually differ in the infrared and ultraviolet spectra. The diamonds are type Ia and Ib contain nitrogen in a combination of different forms. Diamond type Ib contains single substitutional nitrogen atoms or centers. Diamond type Ia contains a combination of different structures of the nitrogen atoms. Diamonds of type IIa have a nitrogen content of less than a few parts per million and can be characterized as diamonds, which do not exhibit essentially no absorption in the range 1332-400 cm-1irradiated by infrared radiation. The diamond is type IIa may have a brown color, due, as I believe, structural deformation within the crystal lattice of the diamond.

In U.S. patent 4124690 described method of converting nitrogen type Ib nitrogen to type Ia in diamond type Ib by high-temperature annealing under pressure, which prevents graphitization. The result of this processing is to reduce the yellow color of the diamond type Ib.

The invention

In accordance with the present invention, a method for changing the color of a diamond, comprising the stage of:

(i) creating a reaction mixture by providing diamond in the PE edusei pressure environment, which completely surrounds the diamond; and

(ii) impact on the reaction mass to high temperature and pressure for a suitable period of time;

characterized in that a diamond is a brown diamond type IIa, and its color change from brown to pink by treatment of the reaction mass temperature in the range from 1900°2300°at a pressure of from 6.9 to 8.5 GPA GPA.

Description of embodiments

In accordance with the present invention, a brown crystal diamond type IIa, which, as a rule, is a natural diamond, is subjected to annealing under pressure, which prevents significant graphitization to modify structural deformation, which causes staining in brown color, and thus reduce brown color and to obtain or enhance the pink color of the diamond. Get pink diamond.

Pink natural diamonds are rare. Thus, in the present invention, a method for obtaining or enhancing pink natural diamond type IIa, without causing damage to the diamond crystal.

A typical absorption spectrum of the diamond type IIa in the infrared region is shown in figure 1. However, not all diamonds are type IIa suitable for color change due to processing at high temperature and high pressure according to the present invention. Diamonds should the s have a brown color, which can vary from dark to light brown, including, for example, pinkish-brown. Those diamonds are type IIa, which is most suitable for the present invention are the nitrogen concentration less than 2 ppm, preferably less than 0.2 parts per million, have colors ranging from brown to pinkish-brown and have a typical absorption spectrum in the ultraviolet and visible region, shown in figure 2 in the form of lines (a), which shows a monotonically increasing absorption or monotonically increasing absorption with wide bands with centers at wavelengths of about 390 and 550 nm, as shown in figure 2 as line (b).

Brown diamond turned into a pink diamond by using an annealing temperature in the range from approximately 1900°With up to approximately 2300°and preferably from 2100°2300°C, under a pressure in the range of from 6.9 to 8.5 GPA GPA, and preferably from about 7.4 to 8.5 HPa HPa, over a period of time, usually located in the interval from 10 minutes to 10 hours, and preferably from 20 minutes to 4 hours. As a rule, the higher the annealing temperature, the shorter the annealing time. Examples of particularly suitable annealing conditions within the specified ranges of pressure values:

2200-2300°C for 1 hour;

2300°during the period of men who e 4 hours and preferably 1 hour;

2100°C for 1 hour.

Color changing crystal diamond type IIa can be quantitatively evaluated due to changes in the absorption spectrum of the crystal, obtained before and after annealing. Absorption spectra of the crystal get at room temperature using a spectrometer in the usual way, which allows to obtain the absorption spectrum of the crystal in the UV and visible region. After annealing the crystal spectra is again at room temperature.

The handling of such diamonds in accordance with the method according to this invention reduces the intensity monotonically increasing absorption and the degree or intensity of the broad absorption bands at wavelengths of 390 and 550 nm; this leads to a more enhanced (saturated) pink color.

In the method according to this invention, the reaction mass is generated by the availability of diamond in a pressure-transmitting medium, which completely surrounds the diamond. Preferably, the reaction mass is generated by sealing a pressure-transmitting medium around the diamond before placing the diamond in the reaction zone of the plant for treatment at a high temperature and high pressure and prior to exposure to the reaction mass to conditions of stage (ii). Transmitting the pressure of the medium is a homogeneous environment, which is fully surrounds the diamond or each of the diamond and which is applied over the entire surface of a diamond or of each of the diamonds. Transmitting the pressure medium is preferably a homogeneous transmitting pressure environment, which provides a uniform distribution of pressure, which is applied over the entire surface of the processed diamond. Examples of suitable media are those that have low shear strength, such as metal salts, for example, halide salts of metals. Transmitting the pressure medium may be a salt of an alkali metal or a salt of the noble metal. Examples of suitable halide salts of metals are potassium bromide, sodium chloride, potassium chloride, cesium chloride, cesium bromide, copper chloride and copper bromide.

It was found that such environments provide the desired uniform distribution of pressure, which ensures that any graphitization that can occur on the surface of the diamond will remain minimal. A special advantage of the use of halide metal salt as a pressure-transmitting medium is that diamonds can be easily extracted after processing by dissolving medium in hot water.

The method according to the invention can be used for processing a single diamond or multiple discrete (separate) diamonds. If handle multiple diamonds at the same time, each diamond must be separated from the neigh boring with them diamonds in a pressure-transmitting medium. The maximum volume of the diamond, which can be subjected to processing is limited only by the capacity of the used setup for processing at high pressure and high temperature.

To implement the method according to the invention it is possible to use the typical installation for processing at high temperature and high pressure. In the patent literature discloses various designs reaction vessels, which provide indirect or direct heating of the reaction mass, and they are suitable for the implementation of the annealing process of the present invention. These reaction vessels are typically composed of many fitted to each other cylindrical elements and end caps or discs for holding the reaction mass in the Central cylinder. In a reaction vessel with indirect heating one of the cylindrical elements made of graphite, which is heated by passing an electric current through it, and which thereby heats the reaction mass. In a reaction vessel with a direct heating of the reaction mass is conductive, avoiding the need to use a cylinder of electrically conductive graphite, and an electric current is passed directly through the reaction mass to heat it.

The invention is illustrated using the following example.

Example 1

Was used natural brown diamond type IIa with the absorption spectrum in the ultraviolet and visible region before processing, shown in figure 3 as line (a). Many of these diamonds was placed in transmitting the pressure medium in the reaction vessel of this type, as illustrated in figure 4. As shown in this figure, the crystals 10 diamonds placed in transmitting the pressure medium 12 so that the crystals were isolated (discrete) and were separated from each other in a pressure-transmitting medium. Diamonds are preferably evenly distributed in the environment. Transmitting the pressure medium is preferably a medium with low resistance to shear of the type indicated above. Containing diamonds Wednesday 12 is placed in the container 14 made of graphite, pyrophyllite, magnesium oxide or zirconium oxide and completely surrounded vzaimopodchinennym metal caps 16, 18, which form a metal enclosure around the container 14. The metal may be molybdenum, tantalum or steel. The housing can be pressed against the container to eliminate air pockets. The container is loaded in the housing is then placed into the reaction zone of a typical installation for processing at high temperature and high pressure. The contents of the capsules were subjected to a temperature of 2250°C and a pressure of 8 GPA, these conditions were maintained for a time period of 4 hours. The capsule was removed from the plant and allowed to cool. Case and graphite container was removed, and the diamonds were extracted from the environment. Absorption spectrum of the diamond in the ultraviolet and visible region after processing is shown in figure 3 as line (b). The spectrum shows the presence of broad bands at a wavelength of 390 and 550 nm, which lead to pink coloration, which was marked.

1. How to change the color of the diamond, which includes stage

(i) creating a reaction mixture by ensuring the presence of diamond in a pressure-transmitting medium, which completely surrounds the diamond; and

(ii) impact on the reaction mass to high temperature and pressure for a suitable period of time;

characterized in that a diamond is a brown diamond type IIa and its color change from brown to pink by treatment of the reaction mass temperature in the range from 1900 to 2300°at a pressure of from 6.9 to 8.5 GPA.

2. The method according to claim 1, characterized in that a diamond is a natural diamond.

3. The method according to claim 1 or 2, characterized in that the diamond has a concentration of nitrogen is less than 2 parts per million, has brown to pinkish-brown and has an absorption spectrum in the ultraviolet and what idivi region, that shows monotonically increasing absorption or monotonically increasing absorption with wide bands with centers at wavelengths of about 390 and 550 nm.

4. The method according to claim 3, characterized in that the nitrogen concentration is less than 0.2 parts per million.

5. The method according to any of the preceding paragraphs, characterized in that the diamond after exposure stage (ii) is characterized by the intensity decrease monotonically increasing absorption and the formation or the intensity of the broad absorption bands at wavelengths of 390 and 550 nm.

6. The method according to any of the preceding items, wherein the temperature in stage (ii) is in the range from 2100 to 2300°C.

7. The method according to any of the preceding paragraphs, characterized in that the pressure in stage (ii) is in the range from 7.4 to 8.5 GPA.

8. The method according to any of the preceding paragraphs, characterized in that the period during which the diamond is exposed to conditions of stage (ii)is from 10 minutes to 10 hours

9. The method according to any one of claims 1 to 7, characterized in that the period during which the diamond is exposed to conditions of stage (ii)is from 20 min to 4 hours

10. The method according to any of the preceding paragraphs, characterized in that the set of diamonds are placed in transmitting pressure environment, with each diamond division is n from its neighboring diamond a pressure-transmitting medium.

11. The method according to any of the preceding items, wherein transmitting the pressure medium is a homogeneous environment, which completely surrounds the diamond or each of the diamond and which is applied over the entire surface of the diamond.

12. The method according to any of the preceding paragraphs, characterized in that the reaction mass is generated by sealing a pressure-transmitting medium around the diamond before placing the diamond in the reaction zone of the plant for treatment at a high temperature and high pressure and influence on the reaction mass to conditions of stage (ii).

13. The method according to any of the preceding items, wherein transmitting pressure environment to a low shear strength.

14. The method according to any of the preceding items, wherein transmitting the pressure medium is soluble in water.

15. The method according to any of the preceding items, wherein transmitting the pressure medium is a salt of the metal.

16. The method according to item 15, wherein transmitting the pressure medium is a halide salt of the metal.

17. The method according to item 16, wherein the halide is a chloride or bromide.

18. The method according to item 15 or 16, wherein transmitting the pressure medium is a salt of an alkali metal.

19. The method according to item 13 or 1, wherein transmitting the pressure medium is a salt of a noble metal.

20. The method according to item 13 or 14, wherein transmitting the pressure medium is a salt of potassium.

21. The method according to item 13 or 14, wherein transmitting the pressure medium is a sodium salt.

22. The method according to item 13 or 14, wherein transmitting the pressure medium is a salt of cesium.

23. The method according to item 13 or 14, wherein transmitting the pressure medium is a salt of copper.

24. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is a bromide of potassium.

25. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is sodium chloride.

26. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is potassium chloride.

27. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is a caesium chloride.

28. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is a bromide cesium.

29. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is a chloride of copper.

30. The method according to any one of claims 1 to 12, wherein transmitting the pressure medium is a bromide m is Dee.



 

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EFFECT: simplified method and improved quality of grown jewelry diamond.

3 cl, 2 tbl

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