A method of reducing the growth of diamond seed cracks

Abstract

The application provides a method for reducing cracks of cultured diamonds, which comprises the following steps: placing a synthetic cavity of a phlogopite containing diamond seeds in a cubic press, pressurizing the cubic press to a set pressure value and performing pressure keeping; increasing the heating power of the cubic press to a set heating power value, and then performing temperature keeping; after a set synthesis time is reached, performing alternating multiple times of temperature reduction and pressure release on the cubic press, wherein the temperature reduction and the pressure release are not synchronized, pressure keeping is performed during the temperature reduction, and temperature keeping is performed during the pressure release, so as to form stepped cross temperature reduction and pressure release; and separating the synthetic cavity of the phlogopite after the synthesis is completed by using a handheld electric grinder, so as to obtain a catalyst block containing cultured diamonds. The method for reducing cracks of cultured diamonds can reduce the internal stress of the cultured diamonds, so that the internal stress of the cultured diamonds can be fully released, the phenomenon of cracks of the cultured diamonds is avoided, the probability of cracks of the cultured diamonds is reduced, and the phenomenon of blasting during the pressure release of the high pressure is avoided.

Description

Technical Field

[0001] This invention relates to the field of lab-grown diamonds, and more specifically, to a method for reducing crystal cracking in lab-grown diamonds. Background Technology

[0002] Currently, lab-grown diamonds are primarily produced using the high-temperature, high-pressure (HTHP) method. This method simulates the high-temperature, high-pressure environment in which diamonds form using a six-sided press, and uses graphite as the raw material. Under the action of a catalyst, the carbon atoms in the graphite rearrange and grow, ultimately forming a rough diamond. Lab-grown diamonds produced using the HTHP method undergo processes such as pressurization, heating, holding, cooling, and depressurization. In existing technologies, the rapid temperature drop during cooling prevents the full release of internal stress within the crystal, leading to cracks and defects, resulting in crystal fissures. Furthermore, the current practice of using forceful hammering to remove the catalyst block containing the lab-grown diamond from the pyrophyllite also increases the probability of crystal fissures.

[0003] To reduce the probability of crystal cracking in lab-grown diamonds, patent application CN116163016A discloses a synthesis method for suppressing crystal cracking in synthetic gem-quality diamonds, including: a ball milling step for pressure-transmitting and heat-insulating materials; and a preparation step for raw materials and auxiliary components.

[0004] The process includes: preparation of raw materials and auxiliary components; baking of assembled components; assembly and heat treatment of the composite block; high-temperature and high-pressure crystal growth; and acid washing and post-treatment to obtain gem-quality diamond single crystals. This synthesis method for suppressing crystal cracking in synthetic gem-quality diamond employs catalyst composition optimization, which effectively inhibits crystal cracking, significantly improves the yield of diamond single crystals, and thus substantially reduces the synthesis cost. However, this method only reduces the crystal cracking rate from the perspective of catalyst composition optimization; the internal stress of the crystal cannot be fully released, which may lead to crystal cracking later. Summary of the Invention

[0005] To reduce internal stress in lab-grown diamonds and ensure its full release, thereby preventing crystal cracking and minimizing the probability of crystal cracking, and to avoid explosions during high-pressure release, the technical solution adopted in this invention is: a method for reducing crystal cracking in lab-grown diamonds, comprising the following steps:

[0006] The synthesis process involves placing a pyrophyllite synthesis chamber containing diamond seed crystals into a six-sided press, pressurizing the press to a set pressure value and maintaining that pressure; then increasing the heating power of the press to a set heating power value and maintaining that temperature.

[0007] After the set synthesis time is reached, the six-sided press is subjected to alternating cooling and depressurization multiple times. The cooling and depressurization are not synchronized. Pressure is maintained during cooling and heat is maintained during depressurization, forming a stepped cross cooling and depressurization process.

[0008] The synthesized pyrophyllite chamber was separated using a handheld electric grinder to obtain a catalyst block containing cultured diamonds.

[0009] Based on the above, in the synthesis step, the six-sided top press is pressurized from atmospheric pressure to the set pressure value in 5 to 10 minutes.

[0010] Based on the above, in the synthesis step, the heating power of the six-sided top press is increased to the set heating power value within 10 to 20 minutes.

[0011] Based on the above, in the synthesis step, the internal pressure of the six-sided press is increased to 5GPa to 7GPa from 5 to 10 minutes, and then the pressure is kept constant while the power is increased. From 10 to 20 minutes, the heating power of the six-sided press is increased to 10KW to 11KW. At this time, the internal temperature of the six-sided press is 1200℃ to 1300℃, and then the power is kept constant.

[0012] Based on the above, in the cooling and depressurization step, after the set synthesis time is reached, the six-sided top press is alternately cooled and depressurized three times.

[0013] During the initial cooling and depressurization, the heating power of the six-sided press is reduced to 70% to 80% of the maximum combined heating power, while the pressure remains constant during the reduction of heating power; then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 70% to 80% of the maximum combined pressure.

[0014] During the second cooling and depressurization, the heating power of the six-sided press is reduced to 50% to 60% of the maximum combined heating power. The pressure remains constant during the reduction of heating power. Then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 40% to 50% of the maximum combined pressure.

[0015] During the third cooling and depressurization process, the heating power of the six-sided press is reduced to 0, while the pressure remains constant during the reduction of heating power. Then, the pressure of the six-sided press is reduced to atmospheric pressure.

[0016] Based on the above, in the cooling and depressurization step, during the first cooling and depressurization, the heating power of the six-sided press is reduced to 70% to 80% of the maximum combined heating power value for 10 to 20 minutes, while the pressure remains constant during the reduction of heating power; then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 70% to 80% of the maximum combined pressure value for 10 to 20 minutes.

[0017] During the second cooling and depressurization, the heating power of the six-sided press is reduced to 50% to 60% of the maximum combined heating power for 20 to 30 minutes. The pressure remains constant during the reduction of heating power. Then, the heating power remains constant, and the pressure of the six-sided press is reduced to 40% to 50% of the maximum combined pressure for 20 to 30 minutes.

[0018] During the third cooling and depressurization, the heating power of the six-sided press is reduced to 0 for 20 to 30 minutes, while the pressure remains constant during the reduction of heating power. Then, the pressure of the six-sided press is reduced to atmospheric pressure for another 20 to 30 minutes.

[0019] Based on the above, in the cooling and depressurization steps, during the first cooling and depressurization, the heating power of the six-sided press is reduced to 80% of the maximum combined heating power value for 20 minutes, while the pressure remains constant during the reduction of heating power; then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 80% of the maximum combined pressure value for 20 minutes.

[0020] During the second cooling and depressurization, the heating power of the six-sided press is reduced to 60% of the maximum combined heating power after 30 minutes. The pressure remains constant during the reduction of heating power. Then, the heating power remains constant, and the pressure of the six-sided press is reduced to 50% of the maximum combined pressure after 30 minutes.

[0021] During the third cooling and depressurization, the heating power of the six-sided press is reduced to 0 within 30 minutes, while the pressure remains constant during the reduction of heating power. Then, the pressure of the six-sided press is reduced to atmospheric pressure within 30 minutes.

[0022] Based on the above, in the separation step, a high-speed steel saw blade with a diameter of 22mm to 35mm and a diamond abrasive grinding wheel with a working surface length of 9mm to 12mm are used to separate the pyrophyllite synthesis cavity after synthesis to obtain a catalyst block containing cultured diamonds.

[0023] Specifically, the main reasons for crystal cracking in lab-grown diamonds are as follows: Internal causes of crystal cracking that cannot be eliminated: The process of preparing lab-grown diamonds using the high temperature and high pressure method involves the crystallization and growth of diamond single crystals in a liquid catalyst solvent. During the growth process, there may be defects such as metal impurities, lattice defects, surface depressions, and polymorphism. If these defects are not handled properly, they will eventually cause crystal cracking in the blank crystal.

[0024] External factors that induce and amplify crystal cracks: During the cooling process after the growth of lab-grown diamonds is completed, the catalyst changes from a liquid to a solid state, and changes in external force during the decompression of the six-sided top press can all induce and amplify internal defects, thus leading to crystal cracks. After decompression, using violent knocking to remove the catalyst block containing lab-grown diamonds from pyrophyllite can also cause some crystal cracks to appear and amplify the degree of crystal cracking.

[0025] This invention has outstanding substantive features and significant progress compared to the prior art. Specifically, this invention provides a method for reducing crystal cracking in lab-grown diamonds. It starts by analyzing the internal and external factors that cause crystal cracking in lab-grown diamonds, and simultaneously adopts a method of step-by-step cooling and depressurization and separation using a small handheld electric grinder. This method can effectively avoid crystal cracking in lab-grown diamonds and significantly reduce the probability of crystal cracking.

[0026] Specifically, the reasons for using a stepped, cross-cooling and depressurization method are as follows: First, maintaining pressure while slowly cooling allows for partial healing of growth defects (internal causes), while preventing the induction and expansion of internal defects due to changes in external forces during depressurization. Second, maintaining temperature while slowly depressurizing ensures that pyrophyllite retains good elastic recovery during depressurization, preventing bursting. Finally, using a stepped, cross-cooling method avoids excessively rapid temperature or pressure drops, which could induce and expand crystal cracking. A small handheld electric grinder is used to avoid the induction and expansion of crystal cracking caused by violent impacts. Attached Figure Description

[0027] Figure 1 This is a photograph of a flawless cultured diamond produced using a method to reduce crystal cracking, as provided by the present invention.

[0028] Figure 2 These are photographs of lab-grown diamonds with surface cracks, prepared using a method provided by a comparative experiment.

[0029] Figure 3 , Figure 4 and Figure 5 These are photographs of lab-grown diamonds with through-cracks, prepared using a method provided by a comparative experiment.

[0030] Figure 6 These are photographs of lab-grown diamonds with surface cracks and through-cracks, prepared using a method provided by comparative experiments. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0032] Example 1

[0033] This embodiment provides a method for reducing crystal cracking in grown diamonds, including the following steps:

[0034] After 5 to 10 minutes of synthesis, the internal pressure of the six-sided press is increased to 5 GPa. Then the pressure is kept constant, and the power is increased. After 10 to 20 minutes, the heating power of the six-sided press is increased to 10 KW. At this time, the internal temperature of the six-sided press is 1200℃. Then the power is kept constant.

[0035] After the set synthesis time is reached, the six-sided press is subjected to three alternating cooling and depressurization cycles. The cooling and depressurization are not synchronized. Pressure is maintained during cooling and heat is maintained during depressurization, forming a stepped cross cooling and depressurization process.

[0036] The synthesized pyrophyllite chamber was separated using a handheld electric grinder to obtain a catalyst block containing cultured diamonds.

[0037] In the cooling and depressurization step, after the set synthesis time is reached, the six-sided press is alternately cooled and depressurized three times. During the first cooling and depressurization, the heating power of the six-sided press is reduced to 80% of the maximum synthesis heating power in 20 minutes, and the pressure remains unchanged during the reduction of heating power. Then, the heating power remains unchanged, and the pressure of the six-sided press is reduced to 80% of the maximum synthesis pressure in 20 minutes.

[0038] During the second cooling and depressurization, the heating power of the six-sided press is reduced to 60% of the maximum combined heating power after 30 minutes. The pressure remains constant during the reduction of heating power. Then, the heating power remains constant, and the pressure of the six-sided press is reduced to 50% of the maximum combined pressure after 30 minutes.

[0039] During the third cooling and depressurization, the heating power of the six-sided press is reduced to 0 within 30 minutes, while the pressure remains constant during the reduction of heating power. Then, the pressure of the six-sided press is reduced to atmospheric pressure within 30 minutes.

[0040] In the separation step, the depressurized pyrophyllite is first separated from the synthetic auxiliary materials by loading a high-speed steel saw blade onto a small handheld electric grinder. When it approaches the catalyst block, the high-speed steel saw blade on the handheld electric grinder is replaced with a diamond grinding needle for further separation, resulting in a catalyst block containing cultured diamonds.

[0041] In this embodiment, the diameter of the high-speed steel saw blade is 22mm, and the working surface length of the diamond grinding needle is 9mm.

[0042] During the experiment, four presses with basically the same environment, state, and position were selected and named Press A, Press B, Press C, and Press D, respectively. The above four six-sided presses were used to repeat this embodiment five times. Finally, the crystal cracking statistics of the cultured diamonds were performed, and the final crystal cracking probabilities were 10.90%, 8.27%, 8.70%, 8.82%, and 10.19%, respectively. Moreover, no backfiring occurred in the six-sided presses during the entire synthesis and depressurization cooling process.

[0043] Example 2

[0044] This embodiment provides a method for reducing crystal cracking in grown diamonds. The main difference from Embodiment 1 is that in this embodiment:

[0045] In the cooling and depressurization step, during the first cooling and depressurization, the heating power of the six-sided press is reduced to 70% of the maximum combined heating power value within 10 minutes, while the pressure remains constant during the reduction of heating power; then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 70% of the maximum combined pressure value within 10 minutes.

[0046] During the second cooling and depressurization, the heating power of the six-sided press was reduced to 50% of the maximum combined heating power after 20 minutes. The pressure remained constant during the reduction of heating power. Then, the heating power remained constant, and the pressure of the six-sided press was reduced to 40% of the maximum combined pressure after 20 minutes.

[0047] During the third cooling and depressurization, the heating power of the six-sided press was reduced to 0 for 20 minutes, while the pressure remained constant during the reduction of heating power. Then, the pressure of the six-sided press was reduced to atmospheric pressure for another 20 minutes.

[0048] During the experiment, four presses with basically the same environment, state, and position were selected and named Press A, Press B, Press C, and Press D, respectively. The above four six-sided presses were used to repeat this embodiment five times. Finally, the crystal cracking statistics of the cultured diamonds were performed, and the final crystal cracking probabilities were 9.33%, 8.56%, 8.75%, 8.91%, and 10.06%, respectively. Moreover, no backfiring occurred in the six-sided presses during the entire synthesis and depressurization cooling process.

[0049] Example 3

[0050] This embodiment provides a method for reducing crystal cracking in grown diamonds. The main difference from Embodiment 1 is that in this embodiment:

[0051] In the cooling and depressurization step, during the first cooling and depressurization, the heating power of the six-sided press is reduced to 75% of the maximum combined heating power in 12 minutes, while the pressure remains constant during the reduction of heating power; then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 74% of the maximum combined pressure in 16 minutes.

[0052] During the second cooling and depressurization, the heating power of the six-sided top press was reduced to 57% of the maximum combined heating power in 26 minutes. The pressure remained constant during the reduction of heating power. Then, the heating power remained constant, and the pressure of the six-sided top press was reduced to 42% of the maximum combined pressure in 22 minutes.

[0053] During the third cooling and depressurization, the heating power of the six-sided press was reduced to 0 after 26 minutes, while the pressure remained constant during the reduction of heating power. Then, the pressure of the six-sided press was reduced to 0 after 27 minutes.

[0054] During the experiment, four presses with basically the same environment, state, and position were selected and named Press A, Press B, Press C, and Press D, respectively. The above four six-sided presses were used to repeat this embodiment five times. Finally, the crystal cracking statistics of the cultured diamonds were performed, and the final crystal cracking probabilities were 10.44%, 9.98%, 8.50%, 8.65%, and 9.33%, respectively. Moreover, no backfire occurred in the six-sided presses during the entire synthesis and depressurization cooling process.

[0055] Comparative Example

[0056] To verify that the method for reducing crystal cracking in lab-grown diamonds provided by this invention effectively reduces the probability of final crystal cracking by simultaneously employing stepped cross-cooling and depressurization and using a handheld electric grinder for separation, the following comparative verification experiment was designed:

[0057] In the experimental conditions, the synthesis steps were the same as those in Example 1, except that the cooling and depressurization steps and the separation steps differed in each comparative example. During the experiment, four presses with essentially the same environment, state, and location were selected and named Press A, Press B, Press C, and Press D, respectively. Each comparative example was repeated five times using these four six-sided presses. Finally, the resulting cultured diamonds were analyzed for crystal cracking. The experimental design and crystal cracking statistics are shown in Tables 1, 2, and 3 below. The synthesized cultured diamonds are shown in... Figures 1 to 6 As shown.

[0058] As can be clearly seen from the figures and the table below, the method of simultaneously employing stepped cross-cooling and depressurization, along with separation using a small handheld electric grinder, effectively avoids crystal cracking in cultured diamonds, significantly reducing the probability of crystal cracking, and also prevents bursting during high-pressure depressurization. Solutions not using the method provided by this invention, or those solely employing stepped cross-cooling and depressurization, or solely using a small handheld electric grinder for separation, do not achieve the same effects as this invention.

[0059] Table 1. Conditions for the test cooling and depressurization steps and separation steps

[0060] Comparative Example 1 direct cooling Direct pressure relief violent separation Comparative Example 2 direct cooling Direct pressure relief Small handheld electric grinder separation Comparative Example 3 Cooling down in 3 stages Pressure was released in three stages. violent separation Comparative Example 4 Cooling down in 3 stages Direct pressure relief violent separation Comparative Example 5 Cooling down in 3 stages Direct pressure relief Small handheld electric grinder separation Comparative Example 6 direct cooling Pressure was released in three stages. violent separation Comparative Example 7 direct cooling Pressure was released in three stages. Small handheld electric grinder separation Example 1 Cooling down in 3 stages Pressure was released in three stages. Small handheld electric grinder separation Example 2 Cooling down in 3 stages Pressure was released in three stages. Small handheld electric grinder separation Example 3 Cooling down in 3 stages Pressure was released in three stages. Small handheld electric grinder separation

[0061] Table 2. Distribution Scheme of the Six-Sided Top Press Machine in the Experiment

[0062]

[0063] Table 3. Crack rate corresponding to different test rounds

[0064]

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for reducing crystal cracking in grown diamonds, comprising the following steps: Synthesis: The pyrophyllite synthesis chamber containing diamond seed crystals is placed in a six-sided press, the six-sided press is pressurized to the set pressure value and held at the pressure; the heating power of the six-sided press is increased to the set heating power value, and then held at the temperature. Cooling and depressurization: After reaching the set synthesis time, the six-sided top press is alternately cooled and depressurized three times. During the first cooling and depressurization, the heating power of the six-sided top press is reduced to 70% to 80% of the maximum synthesis heating power for 10 to 20 minutes, while the pressure remains constant during the reduction of heating power. Then, with the heating power constant, the pressure of the six-sided top press is reduced to 70% to 80% of the maximum synthesis pressure for 10 to 20 minutes. During the second cooling and depressurization, the heating power of the six-sided top press is reduced to 50% to 60% of the maximum combined heating power for 20 to 30 minutes. The pressure remains constant during the reduction of heating power. Then, the heating power remains constant, and the pressure of the six-sided top press is reduced to 40% to 50% of the maximum combined pressure for 20 to 30 minutes. During the third cooling and depressurization, the heating power of the six-sided top press is reduced to 0 for 20 to 30 minutes, while the pressure remains constant during the reduction of heating power. Then, the pressure of the six-sided top press is reduced to atmospheric pressure for 20 to 30 minutes. Separation: The pyrophyllite synthesis chamber after synthesis was separated by high-speed steel saw blades with a diameter of 22mm to 35mm and diamond abrasive grinding wheels with a working surface length of 9mm to 12mm, respectively, to obtain catalyst blocks containing cultured diamonds.

2. The method for reducing crystal cracking in cultured diamonds according to claim 1, characterized in that: In the synthesis step, the six-sided top press is pressurized from atmospheric pressure to the set pressure value in 5 to 10 minutes.

3. The method for reducing crystal cracking in cultured diamonds according to claim 2, characterized in that: During the synthesis step, the heating power of the six-sided top press is increased to the set heating power value within 10 to 20 minutes.

4. The method for reducing crystal cracking in cultured diamonds according to claim 3, characterized in that: In the synthesis step, the internal pressure of the six-sided press is increased to 5GPa to 7GPa from 5 to 10 minutes, and then the pressure is kept constant while the power is increased. From 10 to 20 minutes, the heating power of the six-sided press is increased to 10KW to 11KW, and then the power is kept constant.

5. The method for reducing crystal cracking in cultured diamonds according to claim 4, characterized in that: In the cooling and depressurization step, during the initial cooling and depressurization, the heating power of the six-sided press is reduced to 80% of the maximum combined heating power over 20 minutes, while the pressure remains constant during the reduction of heating power; then, with the heating power remaining constant, the pressure of the six-sided press is reduced to 80% of the maximum combined pressure over 20 minutes. During the second cooling and depressurization, the heating power of the six-sided top press is reduced to 60% of the maximum combined heating power after 30 minutes. The pressure remains constant during the reduction of heating power. Then, the heating power remains constant, and the pressure of the six-sided top press is reduced to 50% of the maximum combined pressure after 30 minutes. During the third cooling and depressurization, the heating power of the six-sided press is reduced to 0 within 30 minutes, while the pressure remains constant during the reduction of heating power. Then, the pressure of the six-sided press is reduced to atmospheric pressure within 30 minutes.

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