Method for treating colored diamonds and brilliants for decolorizing them and releasing stresses

FIELD: decolorizing diamonds and brilliants.

SUBSTANCE: method is realized due to physically acting in closed reaction space upon samples of diamonds and brilliants by means of high pressure and temperature for time period sufficient for enhancing their quality. Pressure acting upon samples is in range 6 - 9 GPa in region of thermodynamic stability. Temperature during physical action upon samples is in range 1700 - 2300°C. Samples are subjected to physical action in medium of graphite powder filling reaction space. Heating till high temperature is realized due to applying AC to samples of diamond or brilliant through graphite powder at specific electric current power from 0.18 kWt/cm3 and more. Then electric power is gradually increased from zero till working value and further it is decreased and increased at least two times for some time interval at each change of electric power. Process of annealing samples is completed by smoothly lowering electric current power till zero. At physical action upon sample electric current intensity is lowered by 11 - 13 % and it is increased by 15 - 17 % for time interval from 8 min and more at each change of electric power. Sample is AC heated and it is cooled at rate no more than 0.05kWt/min per cubic centimeter of reaction volume of chamber.

EFFECT: shortened time period of treating for whole decolorizing, lowered voltage values, keeping of desired parameters existing before treatment in diamonds and brilliants.

3 cl, 3 ex

 

The invention relates to the field of processing of diamonds high pressures at high temperatures and can be used at the enterprises of processing diamonds, discoloration and weakening of the stresses in the crystals.

It is known that one of the main impurities in diamonds is nitrogen, and this mixture can be dispersed in the paramagnetic form, and in aggregate form. Diamonds containing nitrogen, mainly in the dispersion of paramagnetic form, are generally accepted classification of type 1B, and diamonds containing nitrogen mostly in the form of aggregates that are of type 1A. Crystals of type 1 usually colored in shades of brown, yellow-green, and the crystals of type 1A colorless and have a higher hardness compared with crystals of type 1B.

Obviously, under the influence of annealing diamonds at a pressure of 85 Kbar and at a temperature 1850-1960°due to diffusion processes is the transition of doped nitrogen from the dispersed state in the aggregate, i.e. the transition diamonds of type 1 to type 1A diamonds.

A method of processing diamonds, including the impact on diamonds temperatures 1500-2200°and high pressures in the area of its thermodynamic stability. Annealing is carried out in a period of time sufficient to convert at least 20% of dispersed nitrogen in diamonds is aggregated state (French Patent No. 2359071, IPC 01 31/06, publ. 1978).

The disadvantage of this method is the low speed of the process of transformation of one form of nitrogen in diamond to another, due to the achievement of an equilibrium for a given temperature distribution of nitrogen in various forms of its location in the diamond. With significant changes in relative concentrations of nitrogen in the dispersed and aggregated forms are achieved when the duration of the annealing of the crystals measured a few hours, besides the 50% transition of the dispersed nitrogen in aggregated form is not enough to discoloration of the crystals, since the discoloration process is being developed intensively since 70% decrease in the concentration of dispersed nitrogen. Another disadvantage of this method is the appearance of significant stress, contributing to the practical impossibility of adequate mechanical processing of diamonds.

The closest technical solution (prototype) is a method of improving the color of a diamond, comprising the following operations: creating a reaction mixture by ensuring the availability of natural diamond in a pressure-transmitting medium, which completely surrounds the diamond, and the effect on the reaction mass to high temperature and pressure for a suitable period of time, characterized in that the diamond is a brown diamond, its color is menaut from brown to colorless, and the reaction mass is subjected to temperatures in the range from 2200 to 2600°at a pressure of from 7.6 to 9 GPA. Diamond has a concentration of nitrogen of less than 2 million-1shows color from brown to pinkish-brown and has an absorption spectrum in the ultraviolet/visible region, which shows a monotonically increasing absorption or monotonically increasing absorption with wide bands with centers at wavelengths of about 390 and 550 nm.

The temperature during processing is in the range from 2500 to 2550°C. the Period during which the diamond is exposed to conditions of operation does not exceed 5 hours And the reaction mass during processing is subjected to the first stage pressure from 6.9 to 8.5 GPA. The period of heat treatment in the first stage is from 10 minutes to 10 hours, the temperature of the heat treatment in the second stage ranges from 2500 to 2550°C. 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 a diamond or of each of the diamonds. Transmitting pressure environment to a low shear strength and water-soluble (international application (WO) No. 2001/72406, IPC 01 J 3/06, publ. 04.10.2001 year).

The disadvantage of the prototype is the length of the process of crystal samples from 5 to 10 hours is in and more as well as higher temperature processing result can be created additional tension zones in the crystal.

The technical result of the invention is to reduce the time of processing of diamonds with their full discoloration and reduce stress, while maintaining their positive parameters, pre-processing.

This technical result is achieved in that in the method of processing colored diamond or diamonds for bleaching and removing additional stress by physical action in a closed reaction volume of samples diamonds or diamonds of high pressure and temperature for a time sufficient to improve their quality, according to the invention, the pressure exerted on the sample is from 6 to 9 HPa in the region of thermodynamic stability, and the temperature in the process of physical impact is within 1700-2300°With physical effects on the samples is carried out in an environment of graphite powder, which is filled in the reaction volume, temperature heating is carried out the direct influence of an alternating electric current on the samples of diamond or diamond through a graphite powder with a specific electrical power from 0.18 kW/cm3and more, and the power current gradually increases from zero to a slave is what values, with the subsequent reduction and capacity increase of the current at least 2 times with a time delay at each change of electric power, and the exit from the annealing of the samples provide a gradual decrease in the power current to zero.

And in the process of physical impact on the pattern of a diamond or diamond power reduction current is carried out at 11-13%, and increased by 15-17% with time delay at each change of electric capacity from 8 minutes or more. Heating of the sample alternating electrical current and cooling is carried out at a speed of not more than 0.05 kW per minute per cm3the reaction volume of the chamber. The processing time of the proposed method from 60 minutes to 180 minutes, depending on the color and the presence of a defect of the crystal.

Description of the proposed method of handling the diamond or diamonds

The original defective crystals, such as diamonds containing nitrogen, mainly in dispersed form, is placed in the reaction chamber volume high pressure. The crystals are surrounded by a chemically inert with respect to diamond in terms of annealing environment, good transmitting pressure, well conducting electric current, for example a powder of hexagonal graphite.

The treatment is carried out by exposure to a pattern of high pressures in the region of their thermodynamic stability, i.e. the pressure in the chamber is increased up to the values, both the providing process in the region of thermodynamic stability of diamond, then deliver the appropriate power of alternating electric current and carry out the annealing in the specified mode.

When heating an alternating electric current with a speed of not more than 0.05 kW per minute per cm3the reaction volume of the chamber with the sample, achieving a power density of current to 0.18 of 0.47 kW / cm3sample together with conductive filler reaction volume of dielectric container T increased to 1700-2300°under the direct influence of AC on the processing object. Then the temperature and the output current is reduced by 11-13% aged from 8 to 20 min and increase by 15-17% aged from 8 to 20 minutes From the annealing out, reducing the power current with a speed of 0.05 kW per minute per cm3the reaction volume of the chamber with the sample, to the zero power current.

The difference of the proposed method from the known analogues is that the heating is carried out under the direct influence of AC on the processing object to 1700-2300°S, the power current is reduced by 11-13%, then increase by 15-17% with exposure at each temperature from 8 to 20 minutes Additional lowering and raising the capacity of the current repeat 2-3 times with a speed of 0.05 kW per minute per cm3the reaction volume of the chamber with the sample. Final power reduction current to zero is produced at the rate not exceed the overall value of 0.05 kW per minute per cm 3the reaction volume of the chamber with the sample.

Thus, in the first stage of annealing at a temperature of 1700-2300°there is a partial Association of the nitrogen atoms, accompanied by discoloration of diamonds, accelerated by the direct action of electric current in a preheated conductive state of the crystal, the intensity of the Association increases sharply due to the action of alternating current, sharply catalyzing the process of excitation of the atoms disperse nitrogen, the most resistant to the formation of aggregates with carbon, the so-called N3. Further, the speed of the Association decreases in time due to the fall activity diffusion when approaching the relative concentration of dispersed and aggregated nitrogen atoms to equilibrium when the energy of the impact. In the absence of direct passing alternating electric current through the crystal, with indirect heating, the samples of yellow and green shades, containing the stable admixture of nitrogen (N3), not significantly discolored. At temperatures below 1700°With, no noticeable discoloration of diamonds. At a temperature of 2200°With the initial intensity of the Association process of the nitrogen atoms has the greatest value, and at higher temperatures it decreases.

Power reduction current at 11-13%, it is necessary to provide a partial exit in Burdenko status when saving already achieved the Association of nitrogen and activation process further diffusion in the third stage of annealing at a temperature less than the initial. The boundaries of this temperature-power interval determined experimentally: 11% - this is the minimum temperature-power mode, which is required to Wake the system out of balance, and when the temperature-power mode, more than 13% from the initial begins the reverse process - dissociation of nitrogen atoms.

The boundary temperature of the third stage of annealing (15-17% higher than the second stage output system from the equilibrium state) are determined by the same conditions as in the first stage.

The time interval of the temperature of the first and third stages of annealing due to the fact that at smaller 8 min exposures no apparent change in color of the crystals, and at large 30 min exposures, the intensity of the discoloration dramatically slowed. The length of the exposure time for the temperature of the second stage annealing is determined by the need for a strong enough output system crystal admixture of equilibrium, varying depending on the values of the initial annealing temperature in the range from 8 to 20 minutes

Thus, this method involves performing annealing in three stages, with changes in the relative concentrations of dispersed and aggregated nitrogen occurs only on the first and third stages. But the loss of time on the second stage effectively compensated by increasing the front speed of the process of aggregation of nitrogen in diamond crystal. The speed increase and decrease the capacity of the current in the reaction chamber is not more than 0.05 kW min per cm3the reaction volume of the chamber, provide stress relief and prevent parasitic vintage crystal after exposure. These limits the rate of change of output current and temperature is established experimentally.

The proposed mode of annealing allows to reduce the concentration and dispersion, respectively, to increase the concentration of aggregated atoms of impurity nitrogen in diamonds by 80-90%, which is accompanied by almost complete bleaching crystals and stress relief. For crystals containing dispersed nitrogen type N3in quantities of the order of 5-1018cm-3and more, it is necessary to repeat the cycle of annealing 2-3 times, starting with lowering the temperature at 11-13% and subsequent increase relative to the initial values of 2-5%, with these exposures at each temperature, which gives a completely colorless crystals of diamond or diamond from the originally brown, yellow, green and shades. In this case, the authors consistently achieved the aggregation of impurity nitrogen up to 99% of the original. It should be noted that in the process of raising temperature in a sealed chamber there is also a slight increase in pressure in the reaction volume of 20-50% of the initial is O. Because if there is a clear exit from the zone of thermodynamic stability of diamond is not processed crystals are not in danger of graphitization and other damage. In the case of processing diamond polishing surface faces is not disturbed.

Following are experimental examples 1-3 sample processing by the claimed method

EXAMPLE 1.

In the reaction volume of the high-pressure chamber filled with graphite powder, put a diamond with a weight of 2.0 ct with jewelry quality characteristic - 3, color - 7. The number of dispersed nitrogen, also amounted to 5-1018cm-3. Created the initial pressure of 60 Kbar. Heating was carried out direct influence of an alternating electric current to the reaction volume with the sample for 10 minutes prior to the operating temperature of 2200°C. Then the heating power was reduced by 12%, then increased by 16%. After the exposure time for each power mode, 10 min, when the rate of change in heating power 0.05 kW per minute per cm3the reaction volume of the chamber with the sample, removed the power current to zero with the same speed. After mechanical grinding SPECA drew crystal discolored. The characteristics were: as - 2, color - 4. The study faces a 10-fold microscope revealed no defects polishing, as the formation of cracks. The Association of nitrogen was 90%. BP is me processing - 2,5 hours.

EXAMPLE 2.

Initial conditions as in example 1. In the reaction volume was placed three natural diamond - two yellow and one brown with a crack in the area of one vertex, passing to half of the crystal, weight 1,8; 1,9; 2,1 ct, respectively, of octahedral habit. Processing was carried out according to the algorithm of example 1, except for the stage of reducing the output to zero. Then the treatment continued to reduce heat output by 12% and increase power by 5% from the initial value, reiterated this effect three times with the shutter speed in each mode 15 minutes. When the rate of change in heating power 0.05 kW per minute per cm3the reaction volume of the chamber with the sample, removed the power current to zero. After mechanical grinding SPECA learned crystals are completely discolored. The characteristics were: the quality of the edges and surfaces of the ribs without changes, the crack in the third crystal stayed the same. The color of all samples equally missing completely. The study faces a 30-fold microscope revealed no defects polishing, and increase the size of the microcracks. The Association of nitrogen was 97-98% in all three crystals. Processing time is 1.5 hours.

EXAMPLE 3.

Initial conditions as in example 1. In the reaction volume was placed diamond 3,0 ct with quality characteristic - 2, color - 7. The processing carried the or algorithm of example 2. After mechanical grinding of cake, took the crystal is completely discolored. The characteristics were: quality - 2 Color - 1. The study faces a 30-fold microscope revealed no defects polishing, and increase the size of the microcracks. The Association of nitrogen was 99%. Processing time 1 hour.

Thus, the proposed method reduces the processing time of the diamond or diamond from 2 to 10 times while reducing them in tension.

1. The way to handle colored diamond or diamonds for bleaching and removing additional stress by physical action in a closed reaction volume of samples diamonds or diamonds of high pressure and temperature for a time sufficient to improve their quality, characterized in that the pressure exerted on the sample is from 6 to 9 HPa in the region of thermodynamic stability, and the temperature in the process of physical impact is within 1700-2300°With physical effects on the samples is carried out in an environment of graphite powder, which is filled in the reaction volume, temperature warming exercise direct influence of an alternating electric current to samples of diamond or diamond through a graphite powder with a specific electrical power from 0.18 kW/cm3and more, and the power current smoothly veliquat from zero to the set, followed by a decline and an increase in the power current is not less than 2 times with a time delay at each change of electrical power, and the exit from the annealing of the samples provide a gradual decrease in the power current to zero.

2. The method according to claim 1, characterized in that in the process of physical impact on the pattern of a diamond or diamond power reduction current is carried out at 11-13%, and increased by 15-17% with time delay at each change of electric capacity from 8 or more minutes.

3. The method according to claim 1, characterized in that the heating of the sample alternating electrical current and cooling is carried out at a speed of not more than 0.05 kW per minute per cm3the reaction volume of the chamber.



 

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