Colored diamond with stable color system and preparation method thereof

Abstract

The invention relates to the technical field of superhard material synthesis, and particularly discloses a stable-color-system colored diamond and a preparation method thereof.The preparation method comprises the steps that doped diamond is provided; carrying out irradiation treatment and heating and pressurizing treatment on the doped diamond; and cooling and depressurizing the doped diamond subjected to the irradiation treatment and the heating and pressurizing treatment to obtain the stable-color-system colored diamond. According to the preparation method, by accurately controlling the speed and time of temperature and pressure reduction, the residual stress in the diamond crystal can be effectively released, so that doped elements and defects are effectively bonded and more uniformly distributed in the diamond crystal, the color of the diamond is prevented from fluctuating due to environmental change, and the quality of the diamond crystal is improved. The color stability and the structural integrity of the colored diamond are improved, the colored diamonds with different colors and stable color systems can be prepared by controlling the temperature and pressure reduction rate and time, and the requirements of jewelry and industrial application are met.

Description

Technical Field

[0001] The present application relates to the technical field of superhard material synthesis, and in particular to a stable color diamond and a preparation method thereof. Background Art

[0002] Colored diamonds refer to diamonds with significant colors. Most natural diamonds are colorless or slightly yellow, but colored diamonds have always been favored because of their unique aesthetic value and scarcity. The geological conditions for the formation of natural colored diamonds are very special. For example, the only stable source of pink diamonds in the world is the Argyle Mine in Australia. Only one colored diamond can be obtained for every 100,000 rare and high-quality white diamonds produced. Therefore, its market value is much higher than that of colorless diamonds. In recent years, with the continuous development of artificial diamond cultivation technology, the quality of colorless cultivated diamonds has been comparable to that of natural diamonds.

[0003] However, there are still many problems in synthesizing colored diamonds with uniform and stable colors. According to the diamond color theory, there are three main reasons why diamonds are colorful: one is defect coloring; the second is inclusion coloring; and the third is plastic deformation coloring. There are two relatively mature preparation methods. One is to use irradiation treatment to produce a large number of defects inside the diamond to cause coloring. The other is to use high temperature and high pressure methods to introduce coloring inclusions during the diamond growth process to cause coloring.

[0004] In the prior art, artificial colored diamonds are usually prepared using the above two methods or a combination of the above two methods. However, after the sample is heated and pressurized, a certain degree of residual stress and uneven distribution of defects inside the sample will often remain inside the sample. The residual stress will gradually decrease over time, which will lead to a fundamental change in the color uniformity or even color of the sample, ultimately affecting the rating of colored diamonds. Although defects play a vital role in the color of colored diamonds, the formation and control of defects are still a difficult problem that requires fine control during the preparation process, making it impossible for artificially cultivated colored diamonds to achieve the desired color and stable color. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a stable color colored diamond and a preparation method thereof, aiming to solve the problem that artificially cultivated colored diamonds cannot achieve the desired color or stable color.

[0006] The technical solution of this application is as follows:

[0007] In a first aspect of the present application, a method for preparing a stable color colored diamond is provided, comprising: providing a doped diamond; subjecting the doped diamond to irradiation treatment and heating and pressurization treatment; subjecting the doped diamond that has been subjected to the irradiation treatment and heating and pressurization treatment to cooling and pressure reduction treatment to obtain the stable color colored diamond.

[0008] Preferably, the doped diamond is doped with nitrogen, and the doping concentration of the nitrogen is 10PPB-10PPM.

[0009] Preferably, the irradiation dose of the irradiation treatment is 1-200 MGy, and the irradiation treatment time is 1-10 h.

[0010] Preferably, the pressure of the heating and pressurizing treatment is 4-6 GPa, the temperature is 600-2500° C., and the insulation time is 1-300 min.

[0011] Preferably, the heating and pressurizing treatment comprises the steps of: pressing the irradiated doped diamond and the first powder into a sample column in a volume ratio of 1:1-1:5, assembling and baking the sample column with a synthetic block, and then placing the sample column into a six-sided press for heating and pressurizing treatment.

[0012] Preferably, the first powder includes at least one of sodium chloride powder, graphite powder or hexagonal boron chloride powder.

[0013] Preferably, when the pressure reduction rate of the temperature reduction and pressure reduction treatment is 0.02-0.05 GPa / min and the temperature reduction rate is 3-15° C. / min, the stable color colored diamond is in the first color.

[0014] Preferably, when the pressure reduction rate of the temperature reduction and pressure reduction treatment is 0.1-0.2 GPa / min and the temperature reduction rate is 100-300° C. / min, the stable color colored diamond exhibits a second color.

[0015] Preferably, the cooling and pressure reduction treatment further comprises the step of: subjecting the product after the cooling and pressure reduction treatment to acid treatment for purification.

[0016] In a second aspect of the present application, there is provided a stable color colored diamond prepared by the preparation method according to the first aspect of the present application.

[0017] Compared with the prior art, this application has the following advantages:

[0018] The preparation method of the stable color colored diamond in the present application is to cool and depressurize the doped diamond after irradiation and heating and pressurization. By precisely controlling the rate and time of cooling and depressurization, the residual stress in the diamond crystal can be effectively released, so that the doping elements and defects are effectively bonded and more evenly distributed inside the diamond crystal, avoiding the color fluctuation of the diamond due to environmental changes, improving the color stability and structural integrity of the colored diamond, and reducing the risk of fading. And by controlling the rate and time of cooling and depressurization, stable color colored diamonds of different colors can be prepared to meet the needs of jewelry and industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for describing the embodiments are briefly introduced below.

[0020] Figure 1 A schematic diagram of a process for preparing a stable color diamond provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of the structure of the synthesis block provided in the embodiment of the present application;

[0022] Figure 3 A physical picture of the prepared stable pink diamond provided in Example 1 of the present application;

[0023] Figure 4 This is the fluorescence spectrum of diamond before and after the experiment in Example 1 of the present application;

[0024] Figure 5 A physical picture of the unstable color diamond prepared as provided in Example 2 of the present application;

[0025] Figure 6 A physical picture of the prepared stable red diamond provided in Example 3 of the present application;

[0026] Figure 7 This is a physical picture of the prepared stable purple diamond provided in Example 4 of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings and embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present application. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0028] It should be noted that if there are descriptions involving "first", "second", etc. in the implementation of this application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance and implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in the field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0029] In the prior art, it is difficult to control the defect combination and stress distribution inside the diamond during the artificial cultivation of colored diamonds, which makes it impossible for artificially cultivated colored diamonds to achieve the desired color and stable color. Based on this, the present application provides a method for preparing colored diamonds with stable color system, such as Figure 1 As shown, including:

[0030] S1. providing doped diamond;

[0031] S2, subjecting the doped diamond to irradiation treatment and heating and pressurization treatment;

[0032] S3, subjecting the doped diamond that has been irradiated and heated and pressurized to a cooling and pressure reducing process to obtain the stable color colored diamond.

[0033] In some embodiments, the doped diamond is grown by chemical vapor deposition to obtain a single crystal diamond, and the doped diamond is doped with nitrogen, and the doping concentration of the nitrogen element is 10PPB-10PPM, for example, the doping concentration of the nitrogen element is 10PPB, 100PPB, 500PPB, 1000PPB, 2PPM, 5PPM, 8PPM or 10PPM, etc. The doping of nitrogen element can form colored diamonds of yellow, brown, red or pink colors. The single crystal diamond grown by chemical vapor deposition is roughly cut by laser, and the surrounding polycrystalline diamond part is removed to obtain a standardized single crystal diamond initial sample, that is, the doped diamond in S1.

[0034] In some embodiments, the irradiation dose of the irradiation treatment is 1-200 MGy. For example, the irradiation dose of the irradiation treatment is 1 MGy, 10 MGy, 30 MGy, 50 MGy, 60 MGy, 70 MGy, 80 MGy, 90 MGy, 100 MGy, 150 MGy or 200 MGy. The irradiation treatment time is 1-10 h. For example, the irradiation treatment time is 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h. The irradiation treatment can make the doped diamond have vacancy defects, and the irradiation treatment with different irradiation doses can also affect the color of the diamond.

[0035] In some embodiments, the pressure of the heating and pressurizing treatment is 4-6 GPa. For example, the pressure of the heating and pressurizing treatment is 4 GPa, 4.5 GPa, 5 GPa, 5.5 GPa or 6 GPa. The temperature of the heating and pressurizing treatment is 600-2500°C. For example, the temperature of the heating and pressurizing treatment is 600°C, 800°C, 1000°C, 1200°C, 1500°C, 2000°C or 2500°C. The holding time of the heating and pressurizing treatment is 1-300 min. For example, the time of the heating and pressurizing treatment is 1 min, 5 min, 10 min, 50 min, 100 min, 150 min, 200 min, 250 min or 300 min. The heating and pressurizing treatment can accelerate the diffusion and effective bonding of the doping elements and defects inside the diamond, and then more evenly distribute them inside the diamond crystal.

[0036] In some embodiments, the heating and pressurizing treatment includes the steps of: pressing the irradiated doped diamond and the first powder into a sample column in a volume ratio of 1:1-1:5, assembling and baking the synthetic block, and then placing it in a six-sided top press for heating and pressurizing treatment. For example, the volume ratio of the irradiated doped diamond and the first powder is 1:1, 1:2, 1:3, 1:4 or 1:5, etc., wherein the baking time is 10-12 hours. The baking temperature is 150-200°C. The structure of the synthetic block is as follows Figure 2 Preferably, the first powder includes at least one of sodium chloride powder, graphite powder, and hexagonal boron chloride powder. For example, the first powder may be sodium chloride powder, graphite powder, hexagonal boron chloride powder, or a mixed powder of graphite powder and hexagonal boron chloride powder.

[0037] In some embodiments, by precisely controlling the cooling rate and the pressure reduction rate of the cooling and pressure reduction treatment, the residual stress in the diamond crystal can be effectively released, so that the doping elements and defects can be effectively bonded and more evenly distributed inside the diamond crystal, thereby avoiding the color fluctuation of the diamond due to environmental changes and improving the color stability and structural integrity of the colored diamond.

[0038] Furthermore, when the decompression rate of the temperature reduction and pressure reduction treatment is 0.02-0.05 GPa / min and the temperature reduction rate is 3-15°C / min, the stable color colored diamond is in the first color. When the decompression rate of the temperature reduction and pressure reduction treatment is 0.1-0.2 GPa / min and the temperature reduction rate is 100-300°C / min, the stable color colored diamond is in the second color. For example, for diamonds with the same nitrogen doping amount, after irradiation treatment and heating and pressurization treatment, when a slower temperature reduction and pressure reduction rate is used, the stable color colored diamond can appear pink. When a faster temperature reduction and pressure reduction rate is used, the stable color colored diamond can appear purple.

[0039] In some embodiments, the method for preparing stable color diamonds further comprises the steps of:

[0040] S4, subjecting the product after the temperature and pressure reduction treatment to acid treatment for purification.

[0041] The embodiment of the present application also provides a stable color colored diamond prepared by the preparation method as described above.

[0042] The following is further described by means of specific examples.

[0043] Example 1

[0044] (1) Preparation of doped diamond: Single crystal diamond is grown by chemical vapor deposition, and nitrogen is doped during the growth process, with a doping concentration range of 10 PPB-10 PPM to obtain nitrogen-doped single crystal diamond with a diamond size of about 7 mm×7 mm×4 mm. For the specific experimental method, please refer to the patent publication number CN117587512A.

[0045] (2) Irradiation treatment: The nitrogen-doped single crystal diamond is irradiated for 5 h with an irradiation dose of about 100 MGy.

[0046] (3) Heating and Pressurizing Treatment: The irradiated diamond and sodium chloride powder were mixed in a volume ratio of 1:3, and then pressed into a sample column using a tablet press. Figure 2 In the experimental synthetic block shown, after the synthetic block is assembled, it is placed in an oven and baked at 200°C for 12 hours. It is then placed in a domestic six-sided top press for heating and pressurization treatment. The maximum pressure is 6GPa, the temperature is 1000°C, and the insulation time is 60 minutes.

[0047] (4) Cooling and depressurizing treatment: The product of the above heating and pressurizing treatment is slowly cooled and depressurized at a depressurizing rate of 0.02 GPa / min and a cooling rate of 3°C / min. The entire cooling and depressurizing process lasts for 6 hours.

[0048] (5) Post-processing: Take out the synthetic block and treat it with acid for purification. The purified diamond is polished to obtain stable color diamonds, such as Figure 3 As shown. Figure 3 It can be seen that the prepared stable color colored diamond layer is pink. The fluorescence spectrum of the prepared stable color colored diamond was measured, and the results are as follows Figure 4 As shown, from Figure 4 It can be seen that after diamond is irradiated and treated with high temperature and high pressure, obvious NV color centers appear in the diamond, which is the key to the pink color of diamond.

[0049] Example 2

[0050] (1) Preparation of doped diamond: Single crystal diamond is grown by chemical vapor deposition, and nitrogen is doped during the growth process, with a doping concentration range of 10 PPB-10 PPM to obtain nitrogen-doped single crystal diamond with a diamond size of about 7 mm×7 mm×4 mm. For the specific experimental method, please refer to the patent publication number CN117587512A.

[0051] (2) Irradiation treatment: The nitrogen-doped single crystal diamond is irradiated for 5 h with an irradiation dose of about 100 MGy.

[0052] (3) Heating and Pressurizing Treatment: The irradiated diamond and sodium chloride powder were mixed in a volume ratio of 1:3, and then pressed into a sample column using a tablet press. Figure 2 In the experimental synthetic block shown, after the synthetic block is assembled, it is placed in an oven and baked at 200°C for 12 hours. It is then placed in a domestic six-sided top press for heating and pressurization treatment. The maximum pressure is 6GPa, the temperature is 1000°C, and the insulation time is 60 minutes.

[0053] (4) Cooling and depressurizing treatment: The product of the above heating and pressurizing treatment was slowly cooled and depressurized at a depressurizing rate of 0.1 GPa / min and a cooling rate of 300°C / min. The entire cooling and depressurizing process lasted for 4 minutes.

[0054] (5) Post-processing: Take out the synthetic block, treat it with acid for purification, purify it to obtain diamond and polish it, and finally obtain colored diamond, such as Figure 5 As shown. Figure 5 It can be seen that the prepared colored diamond layer appears purple. However, the color of the sample changes significantly after processing.

[0055] Combining Example 1 and Example 2, it can be seen that different cooling rates and pressure reduction rates have an impact on the color of diamond. Specifically, Figure 3For samples that have undergone slow cooling annealing, the sample is pink and the color of the sample does not change after processing. Figure 5 The sample that was annealed at a rapid temperature drop was purple, and the color of the sample changed significantly after processing. That is, the sample that was annealed at a slow temperature drop had a stable color even after cutting and polishing.

[0056] Example 3

[0057] (1) Preparation of doped diamond: Single crystal diamond is grown by chemical vapor deposition, and nitrogen is doped during the growth process, with a doping concentration range of 10 PPB-10 PPM to obtain nitrogen-doped single crystal diamond with a diamond size of about 7 mm×7 mm×4 mm. For the specific experimental method, please refer to the patent publication number CN117587512A.

[0058] (2) Irradiation treatment: The nitrogen-doped single crystal diamond is irradiated for 6 h with an irradiation dose of about 120 MGy.

[0059] (3) Heating and Pressurizing Treatment: The irradiated diamond and sodium chloride powder were mixed in a volume ratio of 1:3, and then pressed into a sample column using a tablet press. Figure 2 In the experimental synthetic block shown, after the synthetic block is assembled, it is placed in an oven and baked at 200°C for 12 hours. It is then placed in a domestic six-sided top press for heating and pressurization treatment. The maximum pressure is 6GPa, the temperature is 1100°C, and the insulation time is 60 minutes.

[0060] (4) Cooling and depressurizing treatment: The product of the above heating and pressurizing treatment is slowly cooled and depressurized at a depressurizing rate of 0.02 GPa / min and a cooling rate of 3°C / min. The entire cooling and depressurizing process lasts for 6 hours.

[0061] (5) Post-processing: Take out the synthetic block and treat it with acid for purification. The purified diamond is polished to obtain stable color diamonds, such as Figure 6 As shown. Figure 6 It can be seen that the prepared stable color diamond layer appears red, and the color of the sample does not change after processing.

[0062] Example 4

[0063] (1) Preparation of doped diamond: Single crystal diamond is grown by chemical vapor deposition, and nitrogen is doped during the growth process, with a doping concentration range of 10 PPB-10 PPM to obtain nitrogen-doped single crystal diamond with a diamond size of about 7 mm×7 mm×4 mm. For the specific experimental method, please refer to the patent publication number CN117587512A.

[0064] (2) Irradiation treatment: The nitrogen-doped single crystal diamond is irradiated for 10 h at a dose of about 200 MGy.

[0065] (3) Heating and Pressurizing Treatment: The irradiated diamond and sodium chloride powder were mixed in a volume ratio of 1:3, and then pressed into a sample column using a tablet press. Figure 2 In the experimental synthetic block shown, after the synthetic block is assembled, it is placed in an oven and baked at 200°C for 12 hours. It is then placed in a domestic six-sided top press for heating and pressurization treatment. The maximum pressure is 6GPa, the temperature is 1300°C, and the insulation time is 60 minutes.

[0066] (4) Cooling and depressurizing treatment: The product of the above heating and pressurizing treatment is slowly cooled and depressurized at a depressurizing rate of 0.02 GPa / min and a cooling rate of 3°C / min. The entire cooling and depressurizing process lasts for 6 hours.

[0067] (5) Post-processing: Take out the synthetic block and treat it with acid for purification. The purified diamond is polished to obtain stable color diamonds, such as Figure 7 As shown. Figure 7 It can be seen that the prepared stable color diamond layer appears purple, and the color of the sample does not change after processing.

[0068] It can be seen from the combination of Example 1, Example 3 and Example 4 that under the conditions of slow temperature and pressure reduction treatment, the color of the stable color diamond does not change after processing.

[0069] In summary, the method for preparing stable color colored diamonds in the present application is to perform a cooling and depressurizing treatment after irradiating the doped diamond and performing a heating and pressurizing treatment. By precisely controlling the rate and time of cooling and depressurizing, the residual stress in the diamond crystal can be effectively released, so that the doping elements and defects are effectively bonded and more evenly distributed inside the diamond crystal, thereby avoiding fluctuations in the color of the diamond due to environmental changes, improving color stability and structural integrity, and by controlling the rate and time of cooling and depressurizing, stable color colored diamonds of different colors (pink, purple, red) can be prepared to meet the needs of jewelry and industrial applications.

[0070] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A method for preparing colored diamonds with stable color, characterized in that: include: Providing doped diamond; The doped diamond is subjected to irradiation treatment and heating and pressure treatment; The doped diamond that has been irradiated and heated and pressurized is subjected to a temperature and pressure reduction treatment to obtain the stable color colored diamond.

2. The preparation method according to claim 1, characterized in that: The doped diamond is doped with nitrogen, and the doping concentration of the nitrogen is 10PPB-10PPM.

3. The preparation method according to claim 1, characterized in that: The irradiation dose of the irradiation treatment is 1-200 MGy, and the irradiation treatment time is 1-10 h.

4. The preparation method according to claim 1, characterized in that: The pressure of the heating and pressurizing treatment is 4-6 GPa, the temperature is 600-2500° C., and the insulation time is 1-300 min.

5. The preparation method according to claim 1, characterized in that: The heating and pressurizing treatment comprises the following steps: The irradiated doped diamond and the first powder are pressed into a sample column in a volume ratio of 1:1-1:5, assembled with a synthesis block and baked, and then placed in a six-sided top press for heating and pressurization treatment.

6. The preparation method according to claim 5, characterized in that: The first powder includes at least one of sodium chloride powder, graphite powder or hexagonal boron chloride powder.

7. The preparation method according to claim 1, characterized in that: When the pressure reduction rate of the temperature reduction and pressure reduction treatment is 0.02-0.05 GPa / min and the temperature reduction rate is 3-15°C / min, the stable color colored diamond is in the first color.

8. The preparation method according to claim 1, characterized in that: When the pressure reduction rate of the temperature reduction and pressure reduction treatment is 0.1-0.2 GPa / min and the temperature reduction rate is 100-300° C. / min, the stable color colored diamond exhibits a second color.

9. The preparation method according to claim 5, characterized in that: The method further comprises the step of: subjecting the product after the cooling and pressure reduction treatment to acid treatment for purification.

10. Colored diamond with stable color prepared by the preparation method according to any one of claims 1 to 9.

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